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Date: Wed, 1 Nov 2017 09:23:44 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: Kate Dawson <k4t@3msg.es>
cc: freebsd-questions@freebsd.org
Subject: Re: FreeBSD ZFS file server with SSD HDD
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On Wed, 11 Oct 2017, Kate Dawson wrote:

> Hi,
>
> Currently running a FreeBSD NFS server with a zpool comprising
>
> 12 x 1TB hard disk drives are arranged as pairs of mirrors in a strip set ( RAID 10 )
>
> An additional 2x 960GB SSD added. These two SSD are partitioned with a
> small partition begin used for a ZIL log, and larger partion arranged for
> L2ARC cache.

For FreeNAS, we recommend against using sharing an SSD like this.  In 
fact, we recommend against using one SSD for anything more than a single 
SLOG for a single pool.  To be effective, this needs to be a low-latency 
SSD, and I/O contention with other shared partitions on the same device 
can negate the performance benefit.