Re: SSD endurance calculations

On 2011-11-21, Christiaan Willemsen <cwillemsen(at)technocon(dot)com> wrote:
>We=
> are looking at beefing up our servers with SSD&#39;s. Some of you did so=
> me interesting tests with the Intel 320. So the idea came to make a RAID1=
> 0 with four 600GB models.</p><p>&nbsp;</p><p>I did however do some calcul=
> ations with the current database server (220GB database, expected to grow=
> to 1TB by the end of next year). I specifically looked at /proc/diskstat=
> at the read/write figures. From there I could see a read/write ratio of =
> 3:1, and I also saw a wopping 170GB of writes per day (for a database tha=
> t currently grows 1GB per dag). That seems like an insanely high figure t=
> o me! How come=3F We do mostly inserts, hardly any updates, virtually no =
> deletes.</p><p>&nbsp;</p><p>Secondly, I also looked at the reliability fi=
> gures of the Intel 320. They show 5 years of 20GB per day, meaning that i=
> t will hold up for about 200 days in our system. RAID 10 wil make 400 day=
> s of that, but this seems hardly a lot.. Am I missing something here=3F</=
> p><p>&nbsp;</p><p>Kind regards,</p><p>&nbsp;</p><p>Christiaan</p><div><p =
> style=3D"font-family: monospace; ">&nbsp;</p></div><p>&nbsp;</p><p>&nbsp;=
></p>=0A</body>=0A</html>

Is your WAL on a separate disk (or set of disks)?

Also, not sure you can fairly conclude that "RAID 10 will make 400 days
of that" -- I had read some posts here a few months back suggesting
that SSDs have been observed to fail very close to each
other in time in a RAID configuration.