[lustre-discuss] Limit client side caching?

Andreas Dilger adilger at whamcloud.com
Tue May 7 15:52:03 PDT 2019

On Apr 22, 2019, at 10:35, Nehring, Shane R [LAS] <snehring at iastate.edu> wrote:
> Hello
> Is there a way to limit the client side caches to a specific size?
> We're occasionally seeing panics due to failed allocations in low
> available memory conditions in our environment. We limit user
> allocations with cgroups through slurm, but it would be handy to
> know exactly how much ram to reserve for system use.

You can limit the size of the client cache via the "max_dirty_mb" and "max_cached_mb" tunables.

There is an aggregate "max_dirty_mb" for the whole client, which is the total amount of unwritten/in-flight dirty data, and a separate "osc.*.max_dirty_mb" tunable (per-OST value) if you want to tune the maximum amount of unwritten data differently for multiple client mountpoints.

The "llite.*.max_cached_mb" is the amount of cached (dirty+clean) cached data for the filesystem.  By default this is 3/4 of RAM.

Cheers, Andreas
Andreas Dilger
Principal Lustre Architect

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