On Mon, 2010-06-07 at 07:51 -0700, Christopher George wrote:
> > No Slogs as I haven't seen a compliant SSD drive yet.
>
> As the architect of the DDRdrive X1, I can state categorically the X1
> correctly implements the SCSI Synchronize Cache (flush cache)
> command.
>
> Christopher George
> Founder/CTO
> www.ddrdrive.com
I can also confirm this, as the author of the first Solaris device
driver for this hardware. (My driver is not what is in the X1 product
though, and that is a topic for a different day.)
Some notes about the X1:
1) its a PCIe x1 form factor, so it isn't a typical SSD
2) it is dependent on an external power source (a little wall wart
provides low voltage power to the card... I don't recall the voltage off
hand)
3) the contents of the card's DDR ram are never flushed to non-volatile
storage automatically, but require an explicit action from the
administrator to save or restore the contents of the DDR to NAND flash.
(This operation takes 60 seconds, during which the card is not
responsive to other commands.)
4) the cost of the device is significantly higher (ISTR $1800, but it
may be less than that) than a typical SSD, with much smaller capacity
(4GB) than typical SSD. But it offers much lower latencies and higher
performance than any other SSD I've encountered.
If you have an extra PCIe slot, an available UPS, and the dollars to
spend, this is a nice little device for use as a ZIL -- my driver was
able to drive I/O all the way to the limit of the PCIe x1 slot easily.
The various caveats for its usage and high per-unit cost probably make
it not practical for the typical home user, though.
-- Garrett
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