Nicholas Lee wrote:
On Thu, Apr 16, 2009 at 3:32 AM, Greg Mason <gma...@msu.edu
<mailto:gma...@msu.edu>> wrote:
And it looks like the Intel fragmentation issue is fixed
as well:
http://techreport.com/discussions.x/16739
FYI, Intel recently had a new firmware release. IMHO, odds are
that
this will be as common as HDD firmware releases, at least for the
next few years.
http://news.cnet.com/8301-13924_3-10218245-64.html?tag=mncol
It should also be noted that the Intel X25-M != the Intel X25-E.
The X25-E hasn't had any of the performance and fragmentation issues.
The X25-E is an SLC SSD, the X25-M is an MLC SSD, hence the more
complex firmware.
Yeah, that's what I understood. I assume based one what I've read and
price on the sun site (11k NZD for 100G Readzilla 17.5k NZD for 18GB
Logzilla) and that the Readizalla's a MLC device (need's more space)
and the Logzilla is a SLC (latency and write speed requirements).
Given latency is the biggest requirement, I'm wondering it would
matter between the X25-E and X25-M for a slog. From the reviews I've
read the latency seems to be pretty similar between the units. Of
course size is not as important for a slog, and given the price for
the 80GB -m and the 30GB -E is very similar it probably would be
better to get the "enterprise" -E.
As for space, 18GBytes is much, much larger than 99.9+% of workloads
require for slog space. Most measurements I've seen indicate that 100
MBytes
will be quite satisfactory for most folks. Unfortunately, there is no
market
for small disk drives -- HDD or SDD.
Another question I'm considering is reliability of SSD units and the
slog. Should a pair of X25-E be mirrored, or given that the pool can
be booted without a slog device is it better to stripe the slog.
Which leads into a second question about slogs - according to [1] as
the stripe size increases for a pool the effectiveness of a SSD slog
reduces. Is still the case?
If you are paranoid, then mirror. For most failure modes, it will be
ok to not mirror.
-- richard
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