On Thu, Jul 02, 2009 at 05:22:54PM +0200, Marek wrote:
5. In case one decides for a partitioned approach - does mdadm kick
out faulty partitions or whole drives? I have read several sources
including some comments on slashdot that it's much better to split
large drives into many small partitions, but noone clarified in
maybe because those suggesting this are not able to come up with a
reasonable explanation?
detail. A possible though unlikely scenario would be simultaneous
failure of all hdds in the array:
md1 RAID6 sda1[_] sdb1[_] sdc1[U] sdd1[U] sde1[U] sdf1[U]
md2 RAID6 sda2[U] sdb2[_] sdc2[_] sdd2[U] sde2[U] sdf2[U]
md3 RAID6 sda3[U] sdb3[U] sdc3[_] sdd3[_] sde3[U] sdf3[U]
md4 RAID6 sda4[U] sdb4[U] sdc4[U] sdd4[_] sde4[_] sdf4[U]
md5 RAID6 sda5[U] sdb5[U] sdc5[U] sdd5[U] sde5[_] sdf5[_]
(...)
If mdadm kicks out faulty partitions only, but leaves the remaining
part of drive going as long as it's able to read it, would it mean
that even if every single hdd in the array failed somewhere (for
example due to Reallocated_Sector_Ct), mdadm would keep the healthy
partitions of that failed drive running, thus the entire system would
be still running in degraded mode without loss of data?
This really depends on your priorities, i would have replaced my drives
well in advance of a similar situation.
The only reason i can imagine for splitting a disk into many partitions
and raiding them together is avoiding lenghty rebuilds when a single
drive is kicked from an array due to a correctable read error.
In practice the above scenario should not happen anymore, since md will
retry writing a stripe if it gets a read-error, besides you are planning
on using raid6, so a single drive failure will still leave you with a
nice degree of protection.
Regards,
L.
--
Luca Berra -- bluca@xxxxxxxxxx
Communication Media & Services S.r.l.
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