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| -rw-r--r-- | debian/mdadm.doc-base.faq | 9 | ||||
| -rw-r--r-- | debian/mdadm.doc-base.md-txt | 11 | ||||
| -rw-r--r-- | debian/mdadm.doc-base.raid5-vs-10 | 11 | ||||
| -rw-r--r-- | debian/mdadm.doc-base.recipes | 9 | ||||
| -rw-r--r-- | debian/mdadm.doc-base.superblock-formats | 10 | ||||
| -rw-r--r-- | debian/mdadm.docs | 1 | ||||
| -rw-r--r-- | md.txt | 185 | ||||
| -rw-r--r-- | md_superblock_formats.txt | 534 |
8 files changed, 732 insertions, 38 deletions
diff --git a/debian/mdadm.doc-base.faq b/debian/mdadm.doc-base.faq new file mode 100644 index 00000000..3fff4504 --- /dev/null +++ b/debian/mdadm.doc-base.faq @@ -0,0 +1,9 @@ +Document: mdadm-faq +Title: mdadm Debian FAQ +Author: martin f. krafft +Abstract: The document answers frequently asked questions about Debian's mdadm +Section: System/Administration + +Format: text +Index: /usr/share/doc/mdadm/FAQ.gz +Files: /usr/share/doc/mdadm/FAQ.gz diff --git a/debian/mdadm.doc-base.md-txt b/debian/mdadm.doc-base.md-txt new file mode 100644 index 00000000..3887026b --- /dev/null +++ b/debian/mdadm.doc-base.md-txt @@ -0,0 +1,11 @@ +Document: mdadm-md-txt +Title: Linux kernel documentation on the md driver (2.6.26) +Author: Neil Brown +Abstract: The document comes from the Linux kernel sources' Documentation/ + directory and contains notes and other information about the md kernel + driver (which mdadm uses). It is current for version 2.6.26 of the kernel. +Section: System/Administration + +Format: text +Index: /usr/share/doc/mdadm/md.txt.gz +Files: /usr/share/doc/mdadm/md.txt.gz diff --git a/debian/mdadm.doc-base.raid5-vs-10 b/debian/mdadm.doc-base.raid5-vs-10 new file mode 100644 index 00000000..47416e53 --- /dev/null +++ b/debian/mdadm.doc-base.raid5-vs-10 @@ -0,0 +1,11 @@ +Document: mdadm-raid5-vs-10 +Title: Comparison of RAID5 and RAID10 +Author: Art S. Kagel +Abstract: This document compares RAID5 and RAID10 and strongly argues against + RAID5. The Debian package maintainer does not agree in full but includes the + document to allow people to make up their own mind. +Section: System/Administration + +Format: text +Index: /usr/share/doc/mdadm/RAID5_versus_RAID10.txt.gz +Files: /usr/share/doc/mdadm/RAID5_versus_RAID10.txt.gz diff --git a/debian/mdadm.doc-base.recipes b/debian/mdadm.doc-base.recipes new file mode 100644 index 00000000..d1069682 --- /dev/null +++ b/debian/mdadm.doc-base.recipes @@ -0,0 +1,9 @@ +Document: mdadm-readme-recipes +Title: mdadm Debian recipes +Author: David Pashley +Abstract: The document contains some common recipes for mdadm usage on Debian +Section: System/Administration + +Format: text +Index: /usr/share/doc/mdadm/README.recipes.gz +Files: /usr/share/doc/mdadm/README.recipes.gz diff --git a/debian/mdadm.doc-base.superblock-formats b/debian/mdadm.doc-base.superblock-formats new file mode 100644 index 00000000..81dc5105 --- /dev/null +++ b/debian/mdadm.doc-base.superblock-formats @@ -0,0 +1,10 @@ +Document: mdadm-superblock-formats +Title: Description of md superblock formats +Author: GrangerX +Abstract: This document details the different md superblock formats and their + disk layouts +Section: System/Administration + +Format: text +Index: /usr/share/doc/mdadm/md_superblock_formats.txt.gz +Files: /usr/share/doc/mdadm/md_superblock_formats.txt.gz diff --git a/debian/mdadm.docs b/debian/mdadm.docs index 830549ad..1adc5b77 100644 --- a/debian/mdadm.docs +++ b/debian/mdadm.docs @@ -8,3 +8,4 @@ md.txt rootraiddoc.97.html RAID5_versus_RAID10.txt davidpashley.com_blog_2008_07_12_rebuilding-raid.html +md_superblock_formats.txt @@ -1,3 +1,11 @@ +# linux-2.6/Documentation/md.txt +# +# From http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob_plain;f=Documentation/md.txt;hb=v2.6.26 +# +# This is md.txt for Linux kernel 2.6.26, which is current in Debian lenny. +# The latest version of this document is at +# http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob_plain;f=Documentation/md.txt;hb=HEAD + Tools that manage md devices can be found at http://www.<country>.kernel.org/pub/linux/utils/raid/.... @@ -62,7 +70,7 @@ be reconstructed (due to no parity). For this reason, md will normally refuse to start such an array. This requires the sysadmin to take action to explicitly start the array -desipite possible corruption. This is normally done with +despite possible corruption. This is normally done with mdadm --assemble --force .... This option is not really available if the array has the root @@ -154,11 +162,12 @@ contains further md-specific information about the device. All md devices contain: level - a text file indicating the 'raid level'. This may be a standard - numerical level prefixed by "RAID-" - e.g. "RAID-5", or some - other name such as "linear" or "multipath". + a text file indicating the 'raid level'. e.g. raid0, raid1, + raid5, linear, multipath, faulty. If no raid level has been set yet (array is still being - assembled), this file will be empty. + assembled), the value will reflect whatever has been written + to it, which may be a name like the above, or may be a number + such as '0', '5', etc. raid_disks a text file with a simple number indicating the number of devices @@ -174,9 +183,24 @@ All md devices contain: raid levels that involve striping (1,4,5,6,10). The address space of the array is conceptually divided into chunks and consecutive chunks are striped onto neighbouring devices. - The size should be atleast PAGE_SIZE (4k) and should be a power + The size should be at least PAGE_SIZE (4k) and should be a power of 2. This can only be set while assembling an array + layout + The "layout" for the array for the particular level. This is + simply a number that is interpretted differently by different + levels. It can be written while assembling an array. + + reshape_position + This is either "none" or a sector number within the devices of + the array where "reshape" is up to. If this is set, the three + attributes mentioned above (raid_disks, chunk_size, layout) can + potentially have 2 values, an old and a new value. If these + values differ, reading the attribute returns + new (old) + and writing will effect the 'new' value, leaving the 'old' + unchanged. + component_size For arrays with data redundancy (i.e. not raid0, linear, faulty, multipath), all components must be the same size - or at least @@ -192,13 +216,11 @@ All md devices contain: 1.2 (newer format in varying locations) or "none" indicating that the kernel isn't managing metadata at all. - level - The raid 'level' for this array. The name will often (but not - always) be the same as the name of the module that implements the - level. To be auto-loaded the module must have an alias - md-$LEVEL e.g. md-raid5 - This can be written only while the array is being assembled, not - after it is started. + resync_start + The point at which resync should start. If no resync is needed, + this will be a very large number. At array creation it will + default to 0, though starting the array as 'clean' will + set it much larger. new_dev This file can be written but not read. The value written should @@ -207,27 +229,52 @@ All md devices contain: available. It will then appear at md/dev-XXX (depending on the name of the device) and further configuration is then possible. - sync_speed_min - sync_speed_max - This are similar to /proc/sys/dev/raid/speed_limit_{min,max} - however they only apply to the particular array. - If no value has been written to these, of if the word 'system' - is written, then the system-wide value is used. If a value, - in kibibytes-per-second is written, then it is used. - When the files are read, they show the currently active value - followed by "(local)" or "(system)" depending on whether it is - a locally set or system-wide value. - - sync_completed - This shows the number of sectors that have been completed of - whatever the current sync_action is, followed by the number of - sectors in total that could need to be processed. The two - numbers are separated by a '/' thus effectively showing one - value, a fraction of the process that is complete. - - sync_speed - This shows the current actual speed, in K/sec, of the current - sync_action. It is averaged over the last 30 seconds. + safe_mode_delay + When an md array has seen no write requests for a certain period + of time, it will be marked as 'clean'. When another write + request arrives, the array is marked as 'dirty' before the write + commences. This is known as 'safe_mode'. + The 'certain period' is controlled by this file which stores the + period as a number of seconds. The default is 200msec (0.200). + Writing a value of 0 disables safemode. + + array_state + This file contains a single word which describes the current + state of the array. In many cases, the state can be set by + writing the word for the desired state, however some states + cannot be explicitly set, and some transitions are not allowed. + + clear + No devices, no size, no level + Writing is equivalent to STOP_ARRAY ioctl + inactive + May have some settings, but array is not active + all IO results in error + When written, doesn't tear down array, but just stops it + suspended (not supported yet) + All IO requests will block. The array can be reconfigured. + Writing this, if accepted, will block until array is quiessent + readonly + no resync can happen. no superblocks get written. + write requests fail + read-auto + like readonly, but behaves like 'clean' on a write request. + + clean - no pending writes, but otherwise active. + When written to inactive array, starts without resync + If a write request arrives then + if metadata is known, mark 'dirty' and switch to 'active'. + if not known, block and switch to write-pending + If written to an active array that has pending writes, then fails. + active + fully active: IO and resync can be happening. + When written to inactive array, starts with resync + + write-pending + clean, but writes are blocked waiting for 'active' to be written. + + active-idle + like active, but no writes have been seen for a while (safe_mode_delay). As component devices are added to an md array, they appear in the 'md' @@ -250,10 +297,18 @@ Each directory contains: faulty - device has been kicked from active use due to a detected fault in_sync - device is a fully in-sync member of the array + writemostly - device will only be subject to read + requests if there are no other options. + This applies only to raid1 arrays. spare - device is working, but not a full member. This includes spares that are in the process - of being recoverred to - This list make grow in future. + of being recovered to + This list may grow in future. + This can be written to. + Writing "faulty" simulates a failure on the device. + Writing "remove" removes the device from the array. + Writing "writemostly" sets the writemostly flag. + Writing "-writemostly" clears the writemostly flag. errors An approximate count of read errors that have been detected on @@ -270,7 +325,7 @@ Each directory contains: This gives the role that the device has in the array. It will either be 'none' if the device is not active in the array (i.e. is a spare or has failed) or an integer less than the - 'raid_disks' number for the array indicating which possition + 'raid_disks' number for the array indicating which position it currently fills. This can only be set while assembling an array. A device for which this is set is assumed to be working. @@ -293,7 +348,7 @@ in the array. These are named rdNN -where 'NN' is the possition in the array, starting from 0. +where 'NN' is the position in the array, starting from 0. So for a 3 drive array there will be rd0, rd1, rd2. These are symbolic links to the appropriate 'dev-XXX' entry. Thus, for example, @@ -343,6 +398,54 @@ also have than sectors, this my be larger than the number of actual errors by a factor of the number of sectors in a page. + bitmap_set_bits + If the array has a write-intent bitmap, then writing to this + attribute can set bits in the bitmap, indicating that a resync + would need to check the corresponding blocks. Either individual + numbers or start-end pairs can be written. Multiple numbers + can be separated by a space. + Note that the numbers are 'bit' numbers, not 'block' numbers. + They should be scaled by the bitmap_chunksize. + + sync_speed_min + sync_speed_max + This are similar to /proc/sys/dev/raid/speed_limit_{min,max} + however they only apply to the particular array. + If no value has been written to these, of if the word 'system' + is written, then the system-wide value is used. If a value, + in kibibytes-per-second is written, then it is used. + When the files are read, they show the currently active value + followed by "(local)" or "(system)" depending on whether it is + a locally set or system-wide value. + + sync_completed + This shows the number of sectors that have been completed of + whatever the current sync_action is, followed by the number of + sectors in total that could need to be processed. The two + numbers are separated by a '/' thus effectively showing one + value, a fraction of the process that is complete. + A 'select' on this attribute will return when resync completes, + when it reaches the current sync_max (below) and possibly at + other times. + + sync_max + This is a number of sectors at which point a resync/recovery + process will pause. When a resync is active, the value can + only ever be increased, never decreased. The value of 'max' + effectively disables the limit. + + + sync_speed + This shows the current actual speed, in K/sec, of the current + sync_action. It is averaged over the last 30 seconds. + + suspend_lo + suspend_hi + The two values, given as numbers of sectors, indicate a range + within the array where IO will be blocked. This is currently + only supported for raid4/5/6. + + Each active md device may also have attributes specific to the personality module that manages it. These are specific to the implementation of the module and could @@ -355,3 +458,9 @@ These currently include there are upper and lower limits (32768, 16). Default is 128. strip_cache_active (currently raid5 only) number of active entries in the stripe cache + preread_bypass_threshold (currently raid5 only) + number of times a stripe requiring preread will be bypassed by + a stripe that does not require preread. For fairness defaults + to 1. Setting this to 0 disables bypass accounting and + requires preread stripes to wait until all full-width stripe- + writes are complete. Valid values are 0 to stripe_cache_size. diff --git a/md_superblock_formats.txt b/md_superblock_formats.txt new file mode 100644 index 00000000..f9c3eb81 --- /dev/null +++ b/md_superblock_formats.txt @@ -0,0 +1,534 @@ +# From: http://linux-raid.osdl.org/index.php/RAID_superblock_formats + +RAID superblock formats + +From Linux-raid + +Jump to: navigation, search + +Contents + + • 1 RAID superblock formats + □ 1.1 The version-0.90 Superblock Format + □ 1.2 The version-1 Superblock Format + □ 1.3 Sub-versions of the version-1 superblock + □ 1.4 The version-1 superblock format on-disk layout + ☆ 1.4.1 Total Size of superblock + ☆ 1.4.2 Section: Superblock/"Magic-Number" Identification area + ☆ 1.4.3 Section: Per-Array Identification & Configuration area + ☆ 1.4.4 Section: RAID-Reshape In-Process Metadata Storage/Recovery + area + ☆ 1.4.5 Section: This-Component-Device Information area + ☆ 1.4.6 Section: Array-State Information area + ☆ 1.4.7 Section: Device-Roles (Positions-in-Array) area + +[edit] + +RAID superblock formats + +Currently, the Linux RAID subsystem recognizes two distinct variant +superblocks. + +They are known as "version-0.90" and "version-1" Superblock formats. + +[edit] + +The version-0.90 Superblock Format + +The version-0.90 superblock format has several limitations. It limits the +number of component devices within an array to 28, and limits each component +device to a maximum size of 2TB. + +[edit] + +The version-1 Superblock Format + +The version-1 superblock format represents a more-expandable format, capable of +supporting arrays with 384+ devices, with 64-bit sector lengths. + +[edit] + +Sub-versions of the version-1 superblock + +The "version-1" superblock format is currently used in three different +"sub-versions". + +The sub-versions differ primarily (solely?) in the location on each component +device at which they actually store the superblock. + +┌───────────┬───────────────────────────────────┐ +│Sub-Version│ Superblock Position on Device │ +├───────────┼───────────────────────────────────┤ +│1.0 │At the end of the device │ +├───────────┼───────────────────────────────────┤ +│1.1 │At the beginning of the device │ +├───────────┼───────────────────────────────────┤ +│1.2 │4K from the beginning of the device│ +└───────────┴───────────────────────────────────┘ +[edit] + +The version-1 superblock format on-disk layout + +[edit] + +Total Size of superblock + +Total Size of superblock: 256 Bytes, plus 2 bytes per device in the array + +[edit] + +Section: Superblock/"Magic-Number" Identification area + +16 Bytes, Offset 0-15 (0x00 - 0x0F) + +┌──────┬──────┬──────┬─────────────┬───────────┬─────┬──────────────────────────┬───────┐ +│Offset│Offset│Length│ │ Usage/ │Data │ │ │ +│(Hex) │(Dec) │ (in │ Field Name │ Meaning │Type │ Data Value │ Notes │ +│ │ │bytes)│ │ │ │ │ │ +├──────┼──────┼──────┼─────────────┼───────────┼─────┼──────────────────────────┼───────┤ +│ │ │ │ │"Magic │ │ │ │ +│0x00 -│0 - 3 │4 │magic │Number" │__u32│0xa92b4efc │ │ +│0x03 │ │ │ │(Superblock│ │(little-endian) │ │ +│ │ │ │ │ID) │ │ │ │ +├──────┼──────┼──────┼─────────────┼───────────┼─────┼──────────────────────────┼───────┤ +│ │ │ │ │Major │ │ │ │ +│0x04 -│4 - 7 │4 │major_version│Version │__u32│1 │ │ +│0x07 │ │ │ │of the │ │ │ │ +│ │ │ │ │Superblock │ │ │ │ +├──────┼──────┼──────┼─────────────┼───────────┼─────┼──────────────────────────┼───────┤ +│ │ │ │ │ │ │0 │ │ +│ │ │ │ │ │ │Bit-Mapped Field │ │ +│ │ │ │ │ │ │ │ │ +│ │ │ │ │ │ │┌─────┬──────────────────┐│ │ +│ │ │ │ │ │ ││ Bit │ Meaning ││ │ +│ │ │ │ │ │ ││Value│ ││ │ +│ │ │ │ │ │ │├─────┼──────────────────┤│ │ +│ │ │ │ │ │ ││1 │RAID Bitmap is ││ │ +│ │ │ │ │ │ ││ │used ││ │ +│ │ │ │ │ │ │├─────┼──────────────────┤│ │ +│ │ │ │ │Feature Map│ ││ │RAID Recovery is ││ │ +│ │ │ │ │- which │ ││2 │in progress ││ │ +│ │ │ │ │extended │ ││ │(See ││ │ +│ │ │ │ │features │ ││ │"recovery_offset")││ │ +│ │ │ │ │(such as │ │├─────┼──────────────────┤│ │ +│0x08 -│ │ │ │volume │ ││4 │RAID Reshape is in││ │ +│0x0B │8 - 11│4 │feature_map │bitmaps, │__u32││ │progress ││ │ +│ │ │ │ │recovery, │ │├─────┼──────────────────┤│ │ +│ │ │ │ │or reshape)│ ││8 │undefined/reserved││ │ +│ │ │ │ │are in use │ ││ │(0) ││ │ +│ │ │ │ │on this │ │├─────┼──────────────────┤│ │ +│ │ │ │ │array │ ││16 │undefined/reserved││ │ +│ │ │ │ │ │ ││ │(0) ││ │ +│ │ │ │ │ │ │├─────┼──────────────────┤│ │ +│ │ │ │ │ │ ││32 │undefined/reserved││ │ +│ │ │ │ │ │ ││ │(0) ││ │ +│ │ │ │ │ │ │├─────┼──────────────────┤│ │ +│ │ │ │ │ │ ││64 │undefined/reserved││ │ +│ │ │ │ │ │ ││ │(0) ││ │ +│ │ │ │ │ │ │├─────┼──────────────────┤│ │ +│ │ │ │ │ │ ││128 │undefined/reserved││ │ +│ │ │ │ │ │ ││ │(0) ││ │ +│ │ │ │ │ │ │└─────┴──────────────────┘│ │ +├──────┼──────┼──────┼─────────────┼───────────┼─────┼──────────────────────────┼───────┤ +│ │ │ │ │ │ │ │Always │ +│0x0C -│12 - │ │ │Padding │ │ │set to │ +│0x0F │15 │4 │pad0 │Block 0 │__u32│0 │zero │ +│ │ │ │ │ │ │ │when │ +│ │ │ │ │ │ │ │writing│ +└──────┴──────┴──────┴─────────────┴───────────┴─────┴──────────────────────────┴───────┘ + + +[edit] + +Section: Per-Array Identification & Configuration area + +48 Bytes, Offset 16-63 (0x10 - 0x3F) + +┌──────┬──────┬──────┬─────────────┬──────────┬─────┬────────────────┬───────────┐ +│Offset│Offset│Length│ │ Usage/ │Data │ │ │ +│(Hex) │(Dec) │ (in │ Field Name │ Meaning │Type │ Data Value │ Notes │ +│ │ │bytes)│ │ │ │ │ │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│0x10 -│16 - │ │ │UUID for │__u8 │Set by │ │ +│0x1F │31 │16 │set_uuid │the Array │[16] │user-space │ │ +│ │ │ │ │(?) │ │formatting util │ │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│0x20 -│32 - │ │ │Name for │char │Set and used by │ │ +│0x3F │63 │32 │set_name │the Array │[32] │user-space utils│Nt │ +│ │ │ │ │(?) │ │ │ │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│ │ │ │ │ │ │low 40-bits are │ │ +│0x40 -│64 - │8 │ctime │Creation │__u64│seconds │ │ +│0x47 │71 │ │ │Time(?) │ │high 24-bits are│ │ +│ │ │ │ │ │ │uSeconds │ │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│ │ │ │ │ │ │┌──┬───────────┐│ │ +│ │ │ │ │ │ ││-4│Multi-Path ││ │ +│ │ │ │ │ │ │├──┼───────────┤│ │ +│ │ │ │ │ │ ││-1│Linear ││ │ +│ │ │ │ │ │ │├──┼───────────┤│ │ +│ │ │ │ │ │ ││0 │RAID-0 ││ │ +│ │ │ │ │ │ ││ │(Striped) ││ │ +│ │ │ │ │ │ │├──┼───────────┤│ │ +│ │ │ │ │ │ ││1 │RAID-1 ││ │ +│ │ │ │ │ │ ││ │(Mirrored) ││mdadm │ +│ │ │ │ │ │ │├──┼───────────┤│versions │ +│ │ │ │ │ │ ││ │RAID-4 ││(as of │ +│ │ │ │ │ │ ││ │(Striped ││v2.6.4) │ +│0x48 -│72 - │ │ │RAID Level│ ││4 │with ││limit │ +│0x4B │75 │4 │level │of the │__u32││ │Dedicated ││RAID-6 │ +│ │ │ │ │Array │ ││ │Block-Level││(creation) │ +│ │ │ │ │ │ ││ │Parity) ││to 256 │ +│ │ │ │ │ │ │├──┼───────────┤│disks or │ +│ │ │ │ │ │ ││ │RAID-5 ││less │ +│ │ │ │ │ │ ││ │(Striped ││ │ +│ │ │ │ │ │ ││5 │with ││ │ +│ │ │ │ │ │ ││ │Distributed││ │ +│ │ │ │ │ │ ││ │Parity) ││ │ +│ │ │ │ │ │ │├──┼───────────┤│ │ +│ │ │ │ │ │ ││ │RAID-6 ││ │ +│ │ │ │ │ │ ││6 │(Striped ││ │ +│ │ │ │ │ │ ││ │with Dual ││ │ +│ │ │ │ │ │ ││ │Parity) ││ │ +│ │ │ │ │ │ │└──┴───────────┘│ │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│ │ │ │ │ │ │┌─┬────────────┐│ │ +│ │ │ │ │ │ ││0│left ││ │ +│ │ │ │ │ │ ││ │asymmetric ││ │ +│ │ │ │ │ │ │├─┼────────────┤│Controls │ +│ │ │ │ │ │ ││1│right ││the │ +│ │ │ │ │layout of │ ││ │asymmetric ││relative │ +│0x4C -│76 - │4 │layout │array │__u32│├─┼────────────┤│arrangement│ +│0x4F │79 │ │ │(RAID5(and│ ││ │left ││of data and│ +│ │ │ │ │6?) only) │ ││2│symmetric ││parity │ +│ │ │ │ │ │ ││ │(default) ││blocks on │ +│ │ │ │ │ │ │├─┼────────────┤│the disks. │ +│ │ │ │ │ │ ││3│right ││ │ +│ │ │ │ │ │ ││ │symmetric ││ │ +│ │ │ │ │ │ │└─┴────────────┘│ │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│ │ │ │ │ │ │size of │ │ +│ │ │ │ │used-size │ │component │ │ +│0x50 -│80 - │8 │size │of │__u64│devices │ │ +│0x57 │87 │ │ │component │ │(in # of │ │ +│ │ │ │ │devices │ │512-byte │ │ +│ │ │ │ │ │ │sectors) │ │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│ │ │ │ │ │ │ │default is │ +│ │ │ │ │ │ │ │64K? for │ +│ │ │ │ │ │ │ │raid levels│ +│ │ │ │ │ │ │ │0, 10, 4, │ +│ │ │ │ │ │ │ │5, and 6 │ +│ │ │ │ │ │ │ │chunksize │ +│ │ │ │ │ │ │ │not used in│ +│ │ │ │ │ │ │ │raid levels│ +│ │ │ │ │ │ │chunk-size of │1, linear, │ +│ │ │ │ │chunk-size│ │the array │and │ +│0x58 -│88 - │4 │chunksize │of the │__u32│(in # of │multi-path │ +│0x5B │91 │ │ │array │ │512-byte │ │ +│ │ │ │ │ │ │sectors) │Note: │ +│ │ │ │ │ │ │ │During │ +│ │ │ │ │ │ │ │creation │ +│ │ │ │ │ │ │ │this │ +│ │ │ │ │ │ │ │appears to │ +│ │ │ │ │ │ │ │be created │ +│ │ │ │ │ │ │ │as a │ +│ │ │ │ │ │ │ │multiple of│ +│ │ │ │ │ │ │ │1024 rather│ +│ │ │ │ │ │ │ │than 512. │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│ │ │ │ │ │ │ │raid4 │ +│ │ │ │ │ │ │ │requires a │ +│ │ │ │ │ │ │ │minimum of │ +│ │ │ │ │ │ │ │2 member │ +│ │ │ │ │ │ │ │devs │ +│ │ │ │ │ │ │ │raid5 │ +│ │ │ │ │ │ │ │requires a │ +│ │ │ │ │ │ │ │minimum of │ +│ │ │ │ │(?)number │ │ │2 member │ +│0x5C -│92 - │4 │raid_disks │of disks │__u32│# │devs │ +│0x5F │95 │ │ │in array │ │ │raid6 │ +│ │ │ │ │(?) │ │ │requires a │ +│ │ │ │ │ │ │ │minimum of │ +│ │ │ │ │ │ │ │4 member │ +│ │ │ │ │ │ │ │devs │ +│ │ │ │ │ │ │ │raid6 │ +│ │ │ │ │ │ │ │limited to │ +│ │ │ │ │ │ │ │a max of │ +│ │ │ │ │ │ │ │256 member │ +│ │ │ │ │ │ │ │devs │ +├──────┼──────┼──────┼─────────────┼──────────┼─────┼────────────────┼───────────┤ +│ │ │ │ │ │ │ │This is │ +│ │ │ │ │# of │ │ │only valid │ +│ │ │ │ │sectors │ │ │if │ +│ │ │ │ │after │ │ │feature_map│ +│ │ │ │ │superblock│ │ │[1] is set │ +│ │ │ │ │that │ │ │ │ +│0x60 -│96 - │4 │bitmap_offset│bitmap │__u32│(signed) │Signed │ +│0x63 │99 │ │ │starts │ │ │value │ +│ │ │ │ │(See note │ │ │allows │ +│ │ │ │ │about │ │ │bitmap │ +│ │ │ │ │signed │ │ │to appear │ +│ │ │ │ │value) │ │ │before │ +│ │ │ │ │ │ │ │superblock │ +│ │ │ │ │ │ │ │on the disk│ +└──────┴──────┴──────┴─────────────┴──────────┴─────┴────────────────┴───────────┘ + + +[edit] + +Section: RAID-Reshape In-Process Metadata Storage/Recovery area + +64 Bytes, Offset 100-163 (0x64 - 0x7F) +(Note: Only contains valid data if feature_map bit '4' is set) + +┌──────┬──────┬──────┬────────────────┬───────────┬─────┬─────────────┬───────┐ +│Offset│Offset│Length│ │ Usage/ │Data │ │ │ +│(Hex) │(Dec) │ (in │ Field Name │ Meaning │Type │ Data Value │ Notes │ +│ │ │bytes)│ │ │ │ │ │ +├──────┼──────┼──────┼────────────────┼───────────┼─────┼─────────────┼───────┤ +│ │ │ │ │the new │ │ │ │ +│0x64 -│100 - │4 │new_level │RAID level │__u32│see level │ │ +│0x67 │103 │ │ │being │ │field (above)│ │ +│ │ │ │ │reshaped-to│ │ │ │ +├──────┼──────┼──────┼────────────────┼───────────┼─────┼─────────────┼───────┤ +│ │ │ │ │Next │ │current │ │ +│0x68 -│104 - │8 │reshape_position│address of │__u64│position of │ │ +│0x6F │111 │ │ │the array │ │the reshape │ │ +│ │ │ │ │to reshape │ │operation │ │ +├──────┼──────┼──────┼────────────────┼───────────┼─────┼─────────────┼───────┤ +├──────┼──────┼──────┼────────────────┼───────────┼─────┼─────────────┼───────┤ +│ │ │ │ │this holds │ │ │ │ +│0x70 -│112 - │4 │delta_disks │the change │__u32│change in # │ │ +│0x73 │115 │ │ │in # of │ │of raid disks│ │ +│ │ │ │ │raid disks │ │ │ │ +├──────┼──────┼──────┼────────────────┼───────────┼─────┼─────────────┼───────┤ +│0x74 -│116 - │4 │new_layout │new layout │__u32│see layout │ │ +│0x77 │119 │ │ │for array │ │field (above)│ │ +├──────┼──────┼──────┼────────────────┼───────────┼─────┼─────────────┼───────┤ +│0x78 -│120 - │4 │new_chunk │new chunk │__u32│see chunksize│ │ +│0x7B │123 │ │ │size │ │field (above)│ │ +├──────┼──────┼──────┼────────────────┼───────────┼─────┼─────────────┼───────┤ +│ │ │ │ │ │ │ │Always │ +│0x7C -│124 - │ │ │Padding │__u8 │ │set to │ +│0x7F │127 │4 │pad1 │Block #1 │[4] │0 │zero │ +│ │ │ │ │ │ │ │when │ +│ │ │ │ │ │ │ │writing│ +└──────┴──────┴──────┴────────────────┴───────────┴─────┴─────────────┴───────┘ + + + +[edit] + +Section: This-Component-Device Information area + +64 Bytes, Offset 128-191 (0x80 - 0xbf) + +┌──────┬──────┬──────┬──────────────────┬────────────┬─────┬────────────────────┬────────────┐ +│Offset│Offset│Length│ │ Usage/ │Data │ │ │ +│(Hex) │(Dec) │ (in │ Field Name │ Meaning │Type │ Data Value │ Notes │ +│ │ │bytes)│ │ │ │ │ │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│0x80 -│128 - │ │ │the sector #│ │sector # where data │ │ +│0x87 │135 │8 │data_offset │upon which │__u64│begins │ │ +│ │ │ │ │data starts │ │(Often 0) │ │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│ │ │ │ │sectors in │ │ │ │ +│0x88 -│136 - │ │ │the device │ │# of sectors that │ │ +│0x8F │143 │8 │data_size │that are │__u64│can be used for data│ │ +│ │ │ │ │used for │ │ │ │ +│ │ │ │ │data │ │ │ │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│ │ │ │ │# of the │ │ │ │ +│0x90 -│144 - │ │ │sector upon │ │# of the sector upon│ │ +│0x97 │151 │8 │super_offset │which this │__u64│which this │ │ +│ │ │ │ │superblock │ │superblock starts │ │ +│ │ │ │ │starts │ │ │ │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│ │ │ │ │sectors │ │ │ │ +│ │ │ │ │before this │ │ │ │ +│0x98 -│152 - │ │ │offset │ │ │ │ +│0x9F │159 │8 │recovery_offset │(from │__u64│sector # │ │ +│ │ │ │ │data_offset)│ │ │ │ +│ │ │ │ │have been │ │ │ │ +│ │ │ │ │recovered │ │ │ │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│0xA0 -│160 - │ │ │ │ │Permanent identifier│ │ +│0xA3 │163 │4 │dev_number │Fm │__u32│of this device (Not │ │ +│ │ │ │ │ │ │its role in RAID(?))│ │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│ │ │ │ │Number of │ │ │ │ +│0xA4 -│164 - │ │ │read-errors │ │ │ │ +│0xA7 │167 │4 │cnt_corrected_read│that were │__u32│Dv │ │ +│ │ │ │ │corrected by│ │ │ │ +│ │ │ │ │re-writing │ │ │ │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│ │ │ │ │UUID of the │ │ │Set by │ +│0xA8 -│168 - │16 │device_uuid │component │__u8 │ │User-Space │ +│0xB7 │183 │ │ │device │[16] │ │Ignored by │ +│ │ │ │ │ │ │ │kernel │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│ │ │ │ │ │ │Bit-Mapped Field │ │ +│ │ │ │ │ │ │ │ │ +│ │ │ │ │ │ │┌─────┬────────────┐│ │ +│ │ │ │ │ │ ││ Bit │ Meaning ││ │ +│ │ │ │ │ │ ││Value│ ││WriteMostly1│ +│ │ │ │ │ │ │├─────┼────────────┤│indicates │ +│ │ │ │ │ │ ││1 │WriteMostly1││that this │ +│ │ │ │ │ │ │├─────┼────────────┤│device │ +│ │ │ │ │ │ ││2 │(?) ││should only │ +│ │ │ │ │Per-Device │ │├─────┼────────────┤│be updated │ +│0xB8 │184 │1 │devflags │Flags │__u8 ││4 │(?) ││on writes, │ +│ │ │ │ │(Bit-Mapped │ │├─────┼────────────┤│not read │ +│ │ │ │ │Field) │ ││8 │(?) ││from. │ +│ │ │ │ │ │ │├─────┼────────────┤│(Useful with│ +│ │ │ │ │ │ ││16 │(?) ││slow devices│ +│ │ │ │ │ │ │├─────┼────────────┤│in RAID1 │ +│ │ │ │ │ │ ││32 │(?) ││arrays?) │ +│ │ │ │ │ │ │├─────┼────────────┤│ │ +│ │ │ │ │ │ ││64 │(?) ││ │ +│ │ │ │ │ │ │├─────┼────────────┤│ │ +│ │ │ │ │ │ ││128 │(?) ││ │ +│ │ │ │ │ │ │└─────┴────────────┘│ │ +├──────┼──────┼──────┼──────────────────┼────────────┼─────┼────────────────────┼────────────┤ +│ │ │ │ │ │ │ │Always set │ +│0xB9 -│185 - │7 │pad2 │Padding │__u8 │0 │to │ +│0xBF │191 │ │ │block 2 │[7] │ │zero when │ +│ │ │ │ │ │ │ │writing │ +└──────┴──────┴──────┴──────────────────┴────────────┴─────┴────────────────────┴────────────┘ + + +[edit] + +Section: Array-State Information area + +64 Bytes, Offset 192-255 (0xC0 - 0xFF) + +┌──────┬──────┬──────┬─────────────┬─────────────┬─────┬────────┬─────────────┐ +│Offset│Offset│Length│ │ │Data │ Data │ │ +│(Hex) │(Dec) │ (in │ Field Name │Usage/Meaning│Type │ Value │ Notes │ +│ │ │bytes)│ │ │ │ │ │ +├──────┼──────┼──────┼─────────────┼─────────────┼─────┼────────┼─────────────┤ +│ │ │ │ │ │ │low │ │ +│ │ │ │ │ │ │40-bits │ │ +│ │ │ │ │ │ │are │ │ +│0xC0 -│192 - │8 │utime │Fm │__u64│seconds │Nt │ +│0xC7 │199 │ │ │ │ │high │ │ +│ │ │ │ │ │ │24-bits │ │ +│ │ │ │ │ │ │are │ │ +│ │ │ │ │ │ │uSeconds│ │ +├──────┼──────┼──────┼─────────────┼─────────────┼─────┼────────┼─────────────┤ +│ │ │ │ │ │ │ │Updated │ +│ │ │ │ │ │ │ │whenever the │ +│ │ │ │ │ │ │ │superblock is│ +│ │ │ │ │ │ │ │updated. │ +│ │ │ │ │ │ │ │Used by mdadm│ +│0xC8 -│200 - │8 │events │Event Count │__u64│# │in │ +│0xCF │207 │ │ │for the Array│ │ │re-assembly │ +│ │ │ │ │ │ │ │to detect │ +│ │ │ │ │ │ │ │failed/ │ +│ │ │ │ │ │ │ │out-of-sync │ +│ │ │ │ │ │ │ │component │ +│ │ │ │ │ │ │ │devices. │ +├──────┼──────┼──────┼─────────────┼─────────────┼─────┼────────┼─────────────┤ +│ │ │ │ │Offsets │ │ │ │ +│ │ │ │ │before this │ │ │ │ +│ │ │ │ │one (starting│ │ │ │ +│0xD0 -│208 - │8 │resync_offset│from │__u64│offset #│ │ +│0xD7 │215 │ │ │data_offset) │ │ │ │ +│ │ │ │ │are 'known' │ │ │ │ +│ │ │ │ │to be in │ │ │ │ +│ │ │ │ │sync. │ │ │ │ +├──────┼──────┼──────┼─────────────┼─────────────┼─────┼────────┼─────────────┤ +│ │ │ │ │ │ │ │This value │ +│ │ │ │ │Checksum of │ │ │will be │ +│0xD8 -│216 - │ │ │this │ │ │different for│ +│0xDB │219 │4 │sb_csum │superblock up│__u32│# │each │ +│ │ │ │ │to devs │ │ │component │ +│ │ │ │ │[max_dev] │ │ │device's │ +│ │ │ │ │ │ │ │superblock. │ +├──────┼──────┼──────┼─────────────┼─────────────┼─────┼────────┼─────────────┤ +│ │ │ │ │How many │ │ │ │ +│0xDC -│220 - │ │ │devices are │ │ │ │ +│0xDF │223 │4 │max_dev │part of (or │__u32│# │ │ +│ │ │ │ │related to) │ │ │ │ +│ │ │ │ │the array │ │ │ │ +├──────┼──────┼──────┼─────────────┼─────────────┼─────┼────────┼─────────────┤ +│0xE0 -│224 - │ │ │Padding Block│__u8 │ │Always set to│ +│0xFF │255 │32 │pad3 │3 │[32] │0 │zero when │ +│ │ │ │ │ │ │ │writing │ +└──────┴──────┴──────┴─────────────┴─────────────┴─────┴────────┴─────────────┘ + + +[edit] + +Section: Device-Roles (Positions-in-Array) area + +Length: Variable number of bytes (but at least 768 bytes?) +2 Bytes per device in the array, including both spare-devices and +faulty-devices + +┌──────────────────────────────────────────────────────────────────────────────┐ +│ Section: Device-Roles (Positions-in-Array) area │ +├──────────────────────────────────────────────────────────────────────────────┤ +│(Variable length - 2 Bytes per Device in Array (including Spares/Faulty-Devs) │ +├──────────────────────────────────────────────────────────────────────────────┤ +│ │ +├────────┬───────┬──────┬─────────┬────────┬─────┬───────────────────────┬─────┤ +│ Offset │Offset │Length│ Field │ Usage/ │Data │ │ │ +│ (Hex) │ (Dec) │ (in │ Name │Meaning │Type │ Data Value │Notes│ +│ │ │bytes)│ │ │ │ │ │ +├────────┴───────┴──────┴─────────┴────────┴─────┴───────────────────────┴─────┤ +│ ?? Bytes, Offset 256-??? (0x100 - 0x???) │ +├────────┬───────┬──────┬─────────┬────────┬─────┬───────────────────────┬─────┤ +│ │ │ │ │ │ │Role or Position of │ │ +│0x100 - │256 │? │dev_roles│Fm │__u16│device in the array. │ │ +│0x??? │- ??? │ │ │ │ │0xFFFF means "spare". │ │ +│ │ │ │ │ │ │0xFFFE means "faulty". │ │ +└────────┴───────┴──────┴─────────┴────────┴─────┴───────────────────────┴─────┘ +Retrieved from "http://linux-raid.osdl.org/index.php/RAID_superblock_formats" + +Views + + • Article + • Discussion + • Edit + • History + +Personal tools + + • Log in / create account + + + +Navigation + + • Linux Raid + • Community portal + • Current events + • Recent changes + • Random page + • Help + • Donations + +Search + +[ ] [Go] [Search] +Toolbox + + • What links here + • Related changes + • Special pages + • Printable version + • Permanent link + +MediaWiki +GNU Free Documentation License 1.2 + + • This page was last modified 04:50, 3 June 2008. + • This page has been accessed 5,723 times. + • Content is available under GNU Free Documentation License 1.2. + • Privacy policy + • About Linux-raid + • Disclaimers + |