freebsd stable - Nov 2015 - ZFS - poor performance with "large" directories

true, but in my experience usb pen drives are variable in terms of
performance across different sticks and different areas of the same stick.
This can complicate things a little, and is often not worth the effort. You
obviously run the ssd over usb though, and I still do on one server I run
as I haven't been able to sort the down time yet.

On 25 November 2015 at 12:16, Gerrit K?hn <gerrit.kuehn at aei.mpg.de>
wrote:
> On Wed, 25 Nov 2015 12:06:38 +0000 krad <kraduk at gmail.com> wrote
about Re:
> ZFS - poor performance with "large" directories:
>
> K> consumer SSDs are cheap enough now not to bother with usb drives I
would
> K> imagine.
>
> Sure. I was just suggesting a USB drive as a quick way to check if this
> might help at all. Most people have USB drives lying around, and they can
> simply be plugged into any computer. A SSD (cheap or not) more likely
> needs to be bought first, and the server box might need to be opened to
> have it installed.
>
>
> cu
>   Gerrit
>

On Thu, Nov 26, 2015 at 2:19 AM, krad <kraduk at gmail.com> wrote:
> true, but in my experience usb pen drives are variable in terms of
> performance across different sticks and different areas of the same stick.
> This can complicate things a little, and is often not worth the effort. You
> obviously run the ssd over usb though, and I still do on one server I run
> as I haven't been able to sort the down time yet.
>
?Nowadays, USB 3.x-based sticks in USB 3.x ports should be fast enough that
they'll be helpful.  You won't get the full 5 Gbps from one (unless you
spend as much or more than an SSD), but it will be much better than the
measly 0.5 Gbps of a USB 2.x stick/port.

Don't bother trying with a USB 2.x stick, or with anything plugged into a
USB 2.x port.  Invariably, it will just slow things down.

I used to use 8 GB USB2 sticks in USB2 ports for L2ARC (with a separate one
for the root filesystem).  When I had 4x IDE disks in a raidz1 vdev?, they
helped.  When I migrated to 4x SATA1 disks in a raidz1 vdev, they helped.
When I migrated to 4x SATA3 disks in dual-mirror vdevs (with root-on-ZFS),
suddenly the USB stick became the bottleneck.  Removing it actually made
the whole system faster (better throughput, more IOps, lower latency,
smoother system overall).

?As always, YMMV, and test it with your own setup.  :)?

-- 
Freddie Cash
fjwcash at gmail.com