[zfs-discuss] Pure SSD Pool

Eric D. Mudama
Sat, 16 Jul 2011 21:49:44 -0000

On Tue, Jul 12 at 23:44, Jim Klimov wrote:
>2011-07-12 23:14, Eric Sproul ?????:
>>So finding drives that keep more space in reserve is key to getting
>>consistent performance under ZFS.
>I think I''ve read in a number of early SSD reviews
>(possibly regarding Intel devices - not certain now)
>that the vendor provided some low-level formatting
>tools which essentially allowed the user to tune how
>much flash would be useable and how much would
>be set aside as the reserve...
>
>Perhaps this rumour is worth an exploration too -
>do any modern SSDs have similar tools to switch
>them between capacity and performance modes,
>or such?

It doesn''t require special tools, just partition the device.

Since ZFS will stay within a partition boundary if told to, that
should allow you to guarantee a certain minimum reserve area available
for other purposes.

e.g. Take a 100GB drive and partition it to 80GB.  Assuming the
original drive was a 100GB/100GiB design, you now have (100*0.07)+20
GB of spare area, which depending on the design, may significantly
lower write amplification and thus increase performance on a device
that is "full."

--eric


--
Eric D. Mudama
edmudama at bounceswoosh.org