Re: change strip_cache_size freeze the whole raid

[Justin Piszcz <jpiszcz@lucidpixels.com>]

On Mon, 22 Jan 2007, kyle wrote:

> Hi,
> 
> Yesterday I tried to increase the value of strip_cache_size to see if I can
> get better performance or not. I increase the value from 2048 to something
> like 16384. After I did that, the raid5 freeze. Any proccess read / write to
> it stucked at D state. I tried to change it back to 2048, read
> strip_cache_active, cat /proc/mdstat, mdadm stop, etc. All didn't return back.
> I even cannot shutdown the machine. Finally I need to press the reset button
> in order to get back my control.
> 
> Kernel is 2.6.17.8 x86-64, running at AMD Athlon3000+, 2GB Ram, 8 x Seagate
> 8200.10 250GB HDD, nvidia chipset.
> 
> cat /proc/mdstat (after reboot):
> Personalities : [raid1] [raid5] [raid4]
> md1 : active raid1 hdc2[1] hda2[0]
>      6144768 blocks [2/2] [UU]
> 
> md2 : active raid5 sdf1[7] sde1[6] sdd1[5] sdc1[4] sdb1[3] sda1[2] hdc4[1]
> hda4[0]
>      1664893440 blocks level 5, 512k chunk, algorithm 2 [8/8] [UUUUUUUU]
> 
> md0 : active raid1 hdc1[1] hda1[0]
>      104320 blocks [2/2] [UU]
> 
> Kyle
> 
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> 

Yes, I noticed this bug too, if you change it too many times or change it 
at the 'wrong' time, it hangs up when you echo numbr > 
/proc/stripe_cache_size.

Basically don't run it more than once and don't run it at the 'wrong' time 
and it works.  Not sure where the bug lies, but yeah I've seen that on 3 
different machines!

Justin.