Re: Deploying PostgreSQL on CentOS with SSD and Hardware RAID

On Fri, May 10, 2013 at 10:19 AM, Matt Brock <mb(at)mattbrock(dot)co(dot)uk> wrote:
> After googling this for a while, it seems that High Endurance MLC is only starting to rival SLC for endurance and write performance in the very latest, cutting-edge hardware. In general, though, it seems it would be fair to say that SLCs are still a better bet for databases than MLC?
>
> The number and capacity of drives is small in this instance, and the price difference between the two for HP SSDs isn't very wide, so cost isn't really an issue. We just want to use whichever is better for the database.

Well, it's more complicated than that. While SLC drives were indeed
inherently faster and had longer lifespans, all flash drives basically
have the requirement of having to carefully manages writes in order to
get good performance. Unfortunately, this means that for database
use the drives must have some type of non-volatile cache and/or
sufficient back up juice in a capacitor to spin out pending write in
the event of sudden loss of power. Many drives, including (famously)
the so-called Intel X25-E "enterprise" lines, did not do this and
where therefore unsuitable for database use.

As it turns out the list of flash drives are suitable for database use
is surprisingly small. The s3700 I noted upthread seems to be
specifically built with databases in mind and is likely the best
choice for new deployments. The older Intel 320 is also a good
choice. I think that's pretty much it until you get into expensive
pci-e based gear. There might be some non-intel drives out there
that are suitable but be very very careful and triple verify that the
drive has on-board capacitor and has gotten real traction in
enterprise database usage.

merlin

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