Re: Kernel 2.6.17 and RAID5 Grow Problem (critical section backup)

From: Justin Piszcz
Date: Fri Jul 07 2006 - 18:13:59 EST




On Sat, 8 Jul 2006, Neil Brown wrote:

On Friday July 7, jpiszcz@xxxxxxxxxxxxxxx wrote:

Jul 7 08:44:59 p34 kernel: [4295845.933000] raid5: reshape: not enough
stripes. Needed 512
Jul 7 08:44:59 p34 kernel: [4295845.962000] md: couldn't update array
info. -28

So the RAID5 reshape only works if you use a 128kb or smaller chunk size?


Neil,

Any comments?


Yes. This is something I need to fix in the next mdadm.
You need to tell md/raid5 to increase the size of the stripe cache
before the grow can proceed. You can do this with

echo 600 > /sys/block/md3/md/stripe_cache_size

Then the --grow should work. The next mdadm will do this for you.

NeilBrown


Hey! You're awake :)

I am going to try it with just 64kb to prove to myself it works with that, but then I will re-create the raid5 again like I had it before and attempt it again, I did not see that documented anywhere!! Also, how do you use the --backup-file option? Nobody seems to know!
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