On Wed, June 16, 2010 03:03, Arne Jansen wrote:
> Christopher George wrote:
>
>> For the record, not all SSDs "ignore cache flushes". There are at least
>> two SSDs sold today that guarantee synchronous write semantics; the
>> Sun/Oracle LogZilla and the DDRdrive X1. Also, I believe it is more
>
> LogZilla? Are these those STEC-thingies? For the price of those I can
> buy a battery backed-up RAID-controller and a few conventional drives.
> For ZIL this will probably do better at a lower price than STEC.
I'm not sure you'd get the same latency and IOps with disk that you can
with a good SSD:
http://blogs.sun.com/brendan/entry/slog_screenshots
You're also talking about using more power (and cooling), and more moving
parts, which can affect reliability numbers. TANSTAAFL.
Towards the bottom of that post Brendan Gregg configures eight Logzillas
(which I'm sure has the cost of a small car), and got 114,000 synchronous
write ops/sec over NFS; 85% of which were done in under 1.21 ms. I'm not
sure how many spindles you'd need to purchase to get numbers like that in
a more "traditional" configuration.
Whether it's worth the cash is another matter entirely.
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