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authormadduck <madduck@3cfab66f-1918-0410-86b3-c06b76f9a464>2006-10-26 18:40:26 +0000
committermadduck <madduck@3cfab66f-1918-0410-86b3-c06b76f9a464>2006-10-26 18:40:26 +0000
commit577ef7c9ac951f20f6697a52ee25fc61f38df0c0 (patch)
tree9f885fef40a0ea0ada8ab562b27a8f4e4626f1a2 /debian/FAQ
parent767210c5fbd689906c7795cacae9904c24d0b113 (diff)
faq updates
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@@ -129,6 +129,9 @@ Also see /usr/share/doc/mdadm/README.recipes.gz
4b. Can a 4-disk RAID10 survive two disk failures?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ I am assuming that you are talking about a setup with two copies of each
+ block, so --layout=near2/far2/offset2:
+
In half of the cases, yes [0], and it does not matter which layout you use.
When you assemble 4 disks into a RAID10, you essentially stripe a RAID0
across two RAID1, so the four disks A,B,C,D become two pairs: A,B and C,D.
@@ -138,7 +141,8 @@ Also see /usr/share/doc/mdadm/README.recipes.gz
Thus, if you see a disk failing, replace it as soon as possible!
If you need to handle two failing disks out of a set of four, you have to
- use RAID6.
+ use RAID6, or store more than two copies of each block (see the --layout
+ option in the mdadm(8) manpage).
0. it's actually 1/(n-1), where n is the number of disks. I am not
a mathematician, see http://aput.net/~jheiss/raid10/