ZFS - poor performance with "large" directories

[krad]

I was referring to the quality of the usb sticks that people have lying
around, rather than the port speed. The biggest thing that flash based
drives have always don is lower latency, as getting throughput out of
magnetic arrays has never been a big issue, random reads/writes a different
story though.

On 26 November 2015 at 16:32, Freddie Cash <fjwcash at gmail.com> wrote:

> 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
>