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Diffstat (limited to 'Documentation/mkfs.btrfs.asciidoc')
| -rw-r--r-- | Documentation/mkfs.btrfs.asciidoc | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/Documentation/mkfs.btrfs.asciidoc b/Documentation/mkfs.btrfs.asciidoc index d53d9e26..f69c529d 100644 --- a/Documentation/mkfs.btrfs.asciidoc +++ b/Documentation/mkfs.btrfs.asciidoc @@ -21,13 +21,8 @@ mount option. See section *MULTIPLE DEVICES* for more details. OPTIONS ------- -*-A|--alloc-start <offset>*:: -(An option to help debugging chunk allocator.) -Specify the (physical) offset from the start of the device at which allocations -start. The default value is zero. - *-b|--byte-count <size>*:: -Specify the size of the filesystem. If this option is not used, +Specify the size of the filesystem. If this option is not used, then mkfs.btrfs uses the entire device space for the filesystem. *-d|--data <profile>*:: @@ -79,7 +74,7 @@ default value is 16KiB (16384) or the page size, whichever is bigger. Must be a multiple of the sectorsize and a power of 2, but not larger than 64KiB (65536). Leafsize always equals nodesize and the options are aliases. + -Smaller node size increases fragmentation but lead to higher b-trees which in +Smaller node size increases fragmentation but leads to taller b-trees which in turn leads to lower locking contention. Higher node sizes give better packing and less fragmentation at the cost of more expensive memory operations while updating the metadata blocks. @@ -135,6 +130,12 @@ Print the *mkfs.btrfs* version and exit. *--help*:: Print help. +*-A|--alloc-start <offset>*:: +*deprecated, will be removed* +(An option to help debugging chunk allocator.) +Specify the (physical) offset from the start of the device at which allocations +start. The default value is zero. + SIZE UNITS ---------- The default unit is 'byte'. All size parameters accept suffixes in the 1024 @@ -166,7 +167,7 @@ root partition created with RAID1/10/5/6 profiles. The mount action can happen before all block devices are discovered. The waiting is usually done on the initramfs/initrd systems. -As of kernel 4.9, RAID5/6 is still considered experimental and shouldn't be +As of kernel 4.14, RAID5/6 is still considered experimental and shouldn't be employed for production use. FILESYSTEM FEATURES @@ -281,9 +282,9 @@ The mkfs utility will let the user create a filesystem with profiles that write the logical blocks to 2 physical locations. Whether there are really 2 physical copies highly depends on the underlying device type. -For example, a SSD drive can remap the blocks internally to a single copy thus +For example, a SSD drive can remap the blocks internally to a single copy--thus deduplicating them. This negates the purpose of increased redundancy and just -wastes filesystem space without the expected level of redundancy. +wastes filesystem space without providing the expected level of redundancy. The duplicated data/metadata may still be useful to statistically improve the chances on a device that might perform some internal optimizations. The actual |