Re: Mount options nodcache and nofsc

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On Fri, May 22, 2015 at 6:14 AM, Erik Logtenberg <erik@xxxxxxxxxxxxx> wrote:
> Hi,
>
> Can anyone explain what the mount options nodcache and nofsc are for,
> and especially why you would want to turn these options on/off (what are
> the pros and cons either way?)

nodcache mount option make cephfs kernel driver not try using kernel
dcache to satisfy readdir(2) and file lookup. readdir and lookup
always go to MDS (it's slow). This mount option is workaround for bugs
in old kernel. we'd better not turn it on for recent kernel.

fsc means fs-cache. it's a kernel facility by which a network
filesystem can cache data locally, trading disk space to gain
performance improvements for access to slow networks and media. cephfs
does not use fs-cache by default.

>
> Thanks,
>
> Erik.
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