On 2/4/2011 7:39 AM, Christopher George wrote:
So, the bottom line is that Solaris 11 Express can not use
TRIM and SSD?
Correct.
So, it might not be a good idea to use a SSD?
It is true that a Flash based SSD, will be adversely impacted by
ZFS not supporting TRIM, especially for the ZIL accelerator.
But a DRAM based SSD is immune to TRIM support status and
thus unaffected. Actually, TRIM support would only add
unnecessary overhead to the DDRdrive X1's device driver.
Best regards,
Christopher George
Founder/CTO
www.ddrdrive.com
Bottom line here is this: for a ZIL, you have a hierarchy of
performance, each about two orders of magnitude faster than the prior:
1. hard drive
2. NAND-based SSD
3. DRAM-based SSD
You'll still get a very noticeable improvement of using a NAND (flash)
SSD over not using a dedicated ZIL device. It just won't be the
improvement "promised" by the SSD packaging.
If that performance isn't sufficient for you, then a DRAM SSD is your
best bet.
Note that even if TRIM would be supported, it wouldn't remove the whole
penalty that a fully-written-to NAND SSD suffers. NAND requires that any
block which was priorly written to be erased BEFORE you can write to it
again. TRIM only helps with using unwritten blocks inside pages, and to
schedule whole page erasures inside the SSD controller. I can't put
real numbers on it, but I would suspect that rather than suffer a 10x
loss of performance, you might only lose 5x or so if TRIM were properly
usable.
--
Erik Trimble
Java System Support
Mailstop: usca22-123
Phone: x17195
Santa Clara, CA
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