> We've experienced a few odd anomalies during testing our IDE RAID-5
> array ( 6 x 16gb =80g).
raidtools 0.90 with raid0145 patches ?
> We simulated a drive failure by disconnecting a drive's power, and if
> the IDE channel contained a second drive in the RAID5 array, the array
> was permanently hosed and couldn't be used, even though the
> RAID5 driver would report that it was running in ok degraded mode (5
> of 6 drives) and ALL remaining drives were functional and could be
> accessed.
"should not happen" :-(
> We reasoned that this was because the second IDE drive (on the
> channel with the failure) temporarily was offline for a brief instant
> during the "failure".
That should only have been noticed it it was accessing the disk at the time.
It would have shown up as having failed.
> Can anyone confirm these findings,
Sounds wrong to me !
> and if so, do they imply that elements of a RAID array must be on seperate
> IDE channels?
If going for speed, I'd so that anyway.
[ I've never been 100% sure whether a "master" disc failure should lose a
"slave" (or vica versa) -- "slave only" works fine ... ]
> It is our impression that the RAID5 array will not gracefully shut down,
... in the case of going below N disks .... pass ...
> and most likely be corrupted if two drives temporarily fail,
I would have hoped that it would just "stop" ...
> or even go off line at once.
same thing as failure as far as the RAID code goes -- I guess it might retry a
bit ...
> Secondly, we had several instances where the RAID5 driver
> reported that it was running in degraded mode with four out of six
> drives functioning (Note: This array had no spares) - a seeming
> impossibility, but the array continued to operate. Is this a bug?
Certainly sounds like it to me !!
> In these cases e2fsck found excessive errors and no data could be used.
No surprise there !!
> Third, we tried restarting the array, sometimes switching drives
> around on different channels
ARGHH !!!!!
> and couldn't get all drives to be properly recognized by the RAID5 driver
Not all thst surprised by that ...
the PSB does include infor about what device it *thinks* it is,
but I'm not sure if that is used to cope with address changes (it would be
nice if it could -- would allow SCSI re-numbering etc ...)
> even though we correctly updated the /etc/raidtab file.
With PSBs, raidtab isn't used !
> Would turning off the persistant-sperblock feature help out here?
Definitely ...
But you really should be using PSBs ...
