[zfs-discuss] Fwd: l2arc fully aggressive settings?

Darik Horn dajhorn at vanadac.com
Tue Sep 15 10:50:02 EDT 2015


On Tue, Sep 15, 2015 at 2:28 AM, HÃ¥kan Johansson
<zfs-discuss at list.zfsonlinux.org> wrote:
>
> I am trying to use ZFS as a replacement for a low-latency file system
> built with MD mirror raid of SSD and (a few) HDDs for resiliency. By
> using the MD option write-mostly for the HDDs, all reads are served
> by the SSD with low latency and high bandwidth.
> (As long as the SSD is alive :) )
>
> I have not been able to find an option to tell a ZFS mirrored pool to
> serve all reads by some specific disks (the SSDs). Is there one?
> (Such an option would be very nice.)

The issue tracker has some technical discussion about optimizing
mirrors that have asymmetric performance.  Start at

* https://github.com/zfsonlinux/zfs/issues/1461

and click into the related issues and enhancement proposals.

I recall that the feature you probably want wasn't added to ZoL
because it had side-effects.  OpenZFS is working on an alternative
here:

* http://wiki.illumos.org/display/illumos/Persistent+L2ARC


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