On 7/25/2011 3:32 AM, Orvar Korvar wrote:
How long have you been using a SSD? Do you see any performance decrease? I mean, ZFS does not support TRIM, so I wonder about long term effects...
Frankly, for the kind of use that ZFS puts on a SSD, TRIM makes no impact whatsoever.
TRIM is primarily useful for low-volume changes - that is, for a filesystem that generally has few deletes over time (i.e. rate of change is low).
Using a SSD as a ZIL or L2ARC device puts a very high write load on the device (even as an L2ARC, there is a considerably higher write load than a "typical" filesystem use). SSDs in such a configuration can't really make use of TRIM, and depend on the internal SSD controller block re-allocation algorithms to improve block layout.
Now, if you're using the SSD as primary media (i.e. in place of a Hard Drive), there is a possibility that TRIM could help. I honestly can't be sure that it would help, however, as ZFS's Copy-on-Write nature means that it tends to write entire pages of blocks, rather than just small blocks. Which is fine from the SSD's standpoint.
On a related note: I've been using a OCZ Vertex 2 as my primary drive in a laptop, which runs Windows XP (no TRIM support). I haven't noticed any dropoff in performance in the year its be in service. I'm doing typical productivity laptop-ish things (no compiling, etc.), so it appears that the internal SSD controller is more than smart enough to compensate even without TRIM.
Honestly, I think TRIM isn't really useful for anyone. It took too long to get pushed out to the OSes, and the SSD vendors seem to have just compensated by making a smarter controller able to do better reallocation. Which, to me, is the better ideal, in any case.
-- Erik Trimble Java Platform Group Infrastructure Mailstop: usca22-317 Phone: x67195 Santa Clara, CA Timezone: US/Pacific (UTC-0800) _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
