On 2017-11-15 04:26, Marat Khalili wrote:
On 15/11/17 10:11, waxhead wrote:
hint: you need more than two for raid1 if you want to stay safe
Huh? Two is not enough? Having three or more makes a difference? (Or,
you mean hot spare?)
They're probably referring to an issue where a two device array
configured for raid1 which had lost a device and was mounted degraded
and writable would generate single profile chunks on the remaining
device instead of a half-complete raid1 chunk. This, when combined with
the fact that older kernels only check the filesystem as a whole for
normal/degraded/irreparable instead of checking individual chunks would
refuse to mount the resultant filesystem, meant that you only had one
chance to fix such an array.
If instead you have more than two devices, regular complete raid1
profile chunks are generated, and it becomes a non-issue.
The second issue (checking degraded status at the chunk level instead of
volume level) has been fixed in the most recent kernels.
The first issue has not been fixed yet, but I'm pretty sure there are
patches pending.
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