[OpenIndiana-discuss] use zfs_nocacheflush

Albert Lee trisk at opensolaris.org
Fri Oct 7 22:36:02 UTC 2011

On Thu, Oct 6, 2011 at 5:45 AM, Gabriele Bulfon <gbulfon at sonicle.com> wrote:
> Hi,
> NFS on zfs can be quite a pain with large number of small files.
> After playing around it, I discovered this zfs_nocacheflush flag bringing me back to high
> performances on NFS.
> Questions:
> - How much unsafe is this?

This is completely unsafe and can easily lead to data loss unless you
have a battery-backed cache. This setting determines whether the cache
is flushed to complete transactions. NFS operations are synchronous.
Use a log device if you want fast synchronous performance, or a mount
option on the client to make operations async (if you don't mind
losing recent NFS writes in the event of a crash). Disabling atimes
may also help.


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