Turn off Linux file cache

Question

How do I turn off write cache in Linux? More specifically, SUSE 11?

My problem is that heavy I/O kills the system even if the generating process is a user priority class, and the starved processes are RR/RT class. So my high availability system breaks with lots of timeouts.

I have / mounted on a flash drive, and a few mount points looking into a RAID controller. For the RAID, I want to try to turn the cache off, since it has a cache inside. But if it needs to be system-wide, fine.

So far I used sync option to mount, but it's not quite like turning off the cache.

Any ideas?

General rule to be real-time is not to mix the workloads, especially batch and interactive tasks. If you want a service to be real-time, then put it on a dedicated server. Otherwise, it would be interesting to hear if ionice suggested below would help alleviate the problem. — Dummy00001, Jul 05 '10 at 22:48

score 10 · Accepted Answer · answered Jul 05 '10 at 14:30

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When mounting your hard drives use -o sync which will turn off write buffering for the drive.

You can also set it up in your fstab:

/dev/sda1    /    reiserfs        sync    0   0

answered Jul 05 '10 at 14:30

amphetamachine

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The OP says he already tried this. – Sjoerd Jul 05 '10 at 14:31
yes, that's actually how you turn off file write caching. When I was asking the question I didn't know enough to ask correctly. Thanks! – n-alexander Aug 20 '10 at 16:49

score 3 · Answer 2 · answered Jul 15 '10 at 10:22

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For a plain hard disk it would normally be

hdparm -W 0 /dev/sdX

but RAID controllers typically don't pass that through.

You'll have to check the configuration interface of your RAID controller for any options. It might not be possible.

answered Jul 15 '10 at 10:22

Peter Eisentraut

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hdparm affects the block device. Linux cache is much higher up – n-alexander Aug 20 '10 at 16:48
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I suppose it depends on which "write cache" he means. – Peter Eisentraut Sep 04 '10 at 11:14

score 1 · Answer 3 · answered Jul 05 '10 at 14:31

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Maybe drop_caches can help you. It does not seem to disable the cache, merely clear it.

answered Jul 05 '10 at 14:31

Sjoerd

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What's wrong with `sync`? – amphetamachine Jul 05 '10 at 14:32

score 0 · Answer 4 · edited Mar 20 '17 at 10:17

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please have a look here: https://superuser.com/a/464382/106740 With http://code.google.com/p/pagecache-mangagement/, you can disable file caches on a per-application level

edited Mar 20 '17 at 10:17

Community

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answered Aug 21 '12 at 13:39

Robert Metzger

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Turn off Linux file cache

4 Answers4

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