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up vote 9 down vote favorite
6

I did

echo 8192 > /sys/block/md0/md/stripe_cache_size

to improve my RAID performance, and it did helped alot.

But I still can't figure out how to make it permanent.

I was trying to set it in /etc/rc.local - other commands are executed, but it was overwritten to 256 elsewhere... Any hints?

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Reposting comment from my answer below; I'm not sure if you saw it or not since I'm not sure how StackExchange works: Hmmm... I don't have RAID, so it's kind of a long shot, but can you try 'grep -R 256 /etc/init.d' and 'grep -R stripe_cache_size /etc/init.d'? – zpletan Jan 15 '11 at 1:45
Would the sysfsutils package help fix your problem? – zpletan Jan 26 '11 at 12:00

7 Answers

up vote 6 down vote accepted
+100

Add a udev rule, e.g. to /etc/udev/rules.d/md-stripe-cache.rules

SUBSYSTEM=="block", KERNEL=="md*", ACTION=="change", TEST=="md/stripe_cache_size", ATTR{md/stripe_cache_size}="8192"

I haven't actually tried this so it might not be 100% right (may be some typos), but it should be close. Check "man udev" to understand more.

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Thank you so much, this is finally perfect solution :-) Syntax is ok, I just had to add 60- before the name, and regenerate ramfs. – BarsMonster Mar 10 '11 at 15:21
up vote 0 down vote

I am also trying to figure this out. I put mine in rc.local and no luck. I start it up manually after logging in. I suppose you could write a script to handle this and put it in your "Startup Applictions" but that doesn't help at all if you're not logged in to gnome.

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It's ubuntu server, so no luck here. – BarsMonster Jan 13 '11 at 6:21
up vote 0 down vote

Would the sysfsutils package help fix your problem?

ORIGINAL ANSWER:

I can't figure out how to comment on your question; I guess I'll edit this answer as I learn more about your problem.

Can you post (or pastebin, if it's long) the output of

grep -R md0 /etc/init.d
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Nothing found there. – BarsMonster Jan 13 '11 at 4:05
Hmmm... I don't have RAID, so it's kind of a long shot, but can you try 'grep -R 256 /etc/init.d' and 'grep -R stripe_cache_size /etc/init.d'? – zpletan Jan 13 '11 at 12:25
both returned no results. – BarsMonster Jan 15 '11 at 9:39
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I don't have a real answer for you, but maybe you could try creating a simple upstart startup script. Create a file in /etc/init with the .conf extension. In the file put:

start on started tty1

exec echo 8192 > /sys/block/md0/md/stripe_cache_size

My thinking is that that should run the command around the time that the terminal has started, which is probably around the same time you are running the command.

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I've already tried to put this in startup script (rc.local) and this didn't helped. Also, as this is Ubuntu Server, no terminals might be there after reboot, AFAIK. – BarsMonster Jan 16 '11 at 21:29
I was proposing this as an alternative to the rc.local method. Maybe it would start later. I don't really know though. – user1974 Jan 17 '11 at 0:41
As for the lack of terminals, I have no idea. Why wouldn't a server have ttys after a startup? Do we mean the same thing when we say terminal? Regardless, you can use a different service to trigger the command, just change tty1 – user1974 Jan 17 '11 at 0:53
up vote 0 down vote

Total shot in the dark as I don't have a RAID 5 setup to test with: Maybe add a line with

chmod -w /sys/block/md0/md/stripe_cache_size

in rc.local to remove the write permissions after it's set. Maybe that will stop it from getting changed elsewhere?

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Good idea, but it seems like something is screwed up in Ubuntu boot process :-S I'll try and post today. – BarsMonster Jan 19 '11 at 10:32
Didn't helped :-| – BarsMonster Jan 21 '11 at 19:03
up vote 0 down vote

This page suggests that stripe size (or width) should have been set up when the fs was set up. Maybe tunefs could help here?

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1  
It's totally different thing. Stripe cache size is a setting for MD kernel driver on memory for stripes cache. – BarsMonster Jan 25 '11 at 8:36
up vote 0 down vote

Append

echo 8192 > /sys/block/mdX/md/stripe_cache_size

to /etc/rc.local.

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See the question - this is the first thing I've tried, and it didn't worked, apparently md-driver was reinitialized or something after rc.local was executed. – BarsMonster Oct 25 '11 at 7:16

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