[ale] Source for Inexpensive, Quiet, Low-Power, rackmount server?

[mike at trausch.us]

On 10/17/2012 10:09 AM, Derek Atkins wrote:
> Have you (or anyone else) done or seen any experimentation with
> MySQL/databases and SSD v. spinning disk?  I would think that RAM would
> be more important unless the full working set is larger than available
> RAM?

MySQL in particular?  No.

I have hit my SSD with a lot of varied workloads, though.  I can tell
you that databases in general incur a lot of overhead with HDDs due to
the fact that the I/O patterns are almost universally nonlinear, even
when performing sequential table scans.  This is because all database
systems that I am aware of perform their I/O in terms of "pages", and
instead of keeping those pages in perfect order, they reuse pages when
they can after deletions occur, meaning that the data inside of such
files tends to become fragmented.  The performance penalty that is
incurred from such fragmentation will virtually disappear when using SSD
media.

I would recommend that you have 2 SSDs mirrored if you're going to do
things that way, and of course, take regular backups.  They are still
new enough that you're going to want to be overcautious about them until
you know how long they'll last for particular workloads.  I would
*expect* that an SSD should be fine for the database component of a DVR;
I wouldn't likely use one for the DVR streams themselves, though, since
(a) you want something huge and (b) you want something that isn't going
to fail in X writes in a relatively predictable fashion.  Even using a
log-structured filesystem, the audio and video easily will overwrite an
SSD several times in the span of a month under relatively "normal" use
patterns.

If you get a slightly more expensive SSD, you can even eliminate the use
of a log-structured FS since they will essentially perform writes in a
ring buffer style as much as possible on the physical media.  This means
that there isn't a 1:1 mapping between a given sector number and its
physical storage cell, but it does mean that wear-leveling occurs
transparently.

In any event, I can say that using an SSD in a "desktop" type
configuration with a DE and using I/O heavy hitters, such as Mozilla
software (which uses many SQLite databases as part of its functionality)
resulted in things being much faster than the moving parts counterparts.
 There is no reason to believe that a bigger DB server would have
massively different characteristics (if anything, my expectation would
be that it would have a bigger benefit, being that devices tend to be
dedicated to the database, and being that random I/O is the name of the
game in that universe).

	--- Mike

-- 
A man who reasons deliberately, manages it better after studying Logic
than he could before, if he is sincere about it and has common sense.
                                   --- Carveth Read, “Logic”

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