Well, it seems that my data can be outdated, sorry for that. I've just checked performance numbers on Tom's hardware and it seems that best sad really do 500 MB/s. Some others do 100. So, I'd say one must choose wisely (as always :-) ).
Best regards,
Vitalii Tymchyshyn
1 груд. 2012 00:43, "Mark Kirkwood" <
mark.kirkwood@catalyst.net.nz> напис.
Hmm - not strictly true as stated: 1 SSD will typically do 500MB/s sequential read/write. 1 HDD will be lucky to get a 1/3 that.
We are looking at replacing 4 to 6 disk RAID10 arrays of HDD with a RAID1 pair of SSD, as they perform about the same for sequential work and vastly better at random. Plus they only use 2x 2.5" slots (or, ahem 2x PCIe sockets), so allow smaller form factor servers and save on power and cooling.
Cheers
Mark
On 30/11/12 23:07, Vitalii Tymchyshyn wrote:
Oh, yes. I don't imagine DB server without RAID+BBU :)
When there is no BBU, SSD can be handy.
But you know, SSD is worse in linear read/write than HDD.
Best regards, Vitalii Tymchyshyn
2012/11/30 Mark Kirkwood <mark.kirkwood@catalyst.net.nz
<mailto:mark.kirkwood@catalyst.net.nz>>
Most modern SSD are much faster for fsync type operations than a
spinning disk - similar performance to spinning disk + writeback
raid controller + battery.
However as you mention, they are great at random IO too, so Niels,
it might be worth putting your postgres logs *and* data on the SSDs
and retesting.