Re: change strip_cache_size freeze the whole raid

[Liang Yang]

Do we need to consider the chunk size when we adjust the value of 
Striped_Cache_Szie for the MD-RAID5 array?

Liang

----- Original Message ----- 
From: "Justin Piszcz" <jpiszcz@xxxxxxxxxxxxxxx>
To: "kyle" <kylewong@xxxxxxxxxx>
Cc: <linux-raid@xxxxxxxxxxxxxxx>; <linux-kernel@xxxxxxxxxxxxxxx>
Sent: Monday, January 22, 2007 5:18 AM
Subject: Re: change strip_cache_size freeze the whole raid


> 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.
>
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