On 06/07/2009, at 9:31 AM, Ross Walker wrote:
There are two types of SSD drives on the market, the fast write SLC
(single level cell) and the slow write MLC (multi level cell). MLC
is usually used in laptops as SLC drives over 16GB usually go for
$1000+ which isn't cost effective in a laptop. MLC is good for read
caching though and most use it for L2ARC.
I just ordered a bunch of 16GB Imation Pro 7500's (formerly Mtron)
from CDW lately for $290 a pop. They are suppose to be fast
sequential write SLC drives and so-so random write. We'll see.
That will be interesting to see.
The Samsung drives we have are 50GB (64GB) SLC and apparently 2nd
generation.
For a slog, is random write even an issue? Or is it just the
mechanism used to measure the IOPS performance of a typical device?
AFAIUI, the ZIL is used as a ring buffer. How does that work with an
SSD? All this pain really makes me think the only sane slog is one
that is RAM based and has enough capacitance to either make itself
permanent or move the data to something permanent before failing
(FusionIO, DDRdrive, for example).
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