[zfs-discuss] Pure SSD Pool

Bob Friesenhahn
Tue, 12 Jul 2011 16:01:05 -0000

On Tue, 12 Jul 2011, Eric Sproul wrote:
>
> Now, others have hinted that certain controllers are better than
> others in the absence of TRIM, but I don''t see how GC could know
what
> blocks are available to be erased without information from the OS.

Drives which keep spare space in reserve (as any responsible product
will do) can be assured that any flash block which is requested to
overwritten is available to be erased.  The main issue occurs when the
overwrites don''t span a flash erasure block since then the SSD
controller needs to make a value judgement about what to do.

> Those with deep knowledge of SSD models/controllers: how does the
> Intel 320 perform under ZFS as primary storage (not ZIL or L2ARC)?

My biggest fear with using consumer SSDs is if the SSD properly honors
cache flush requests.  If cache flush requests are not properly
honored, then the pool could be bricked (or at least require a
recovery action) due to a power failure.

Bob
--
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/