On 7/5/09 11:13 PM, "Mark Kirkwood" <mar...@paradise.net.nz> wrote:
> Craig Ringer wrote: >> On Sat, 2009-07-04 at 11:51 -0700, Patvs wrote: >> >> >> >>> With 4 regular harddisks in RAID0 you get great read/write speeds, but the >>> SSDs excel in IO/s and a 0.1ms access time. >>> >> >> ... but are often really, really, really, really slow at writing. The >> fancier ones are fast at writing but generally slow down over time. >> >> > > Also, (probably pointing out the obvious here) to be on the safe side > you should avoid RAID0 for any data that is important to you - as it's > pretty easy to get one bad disk straight from new! > > With respect to SSD's one option for a small sized database is 2xSSD in > RAID1 - provided they are the *right* SSD that is, which at this point > in time seems to be the Intel X25E. Note that I have not benchmarked > this configuration, so no guarantees that it (or the Intel SSDs > themselves) are as good as the various on-the-web tests indicate! There is no reason to go RAID 1 with SSD's if this is an end-user box and the data is recoverable. Unlike a hard drive, a decent SSD isn't expected to go bad. I have deployed over 150 Intel X25-M's and they all work flawlessly. Some had the 'slowdown' problem due to how they were written to, but the recent firmware fixed that. At this point, I consider a single high quality SSD as more fault tolerant than software raid-1. Unless there are lots of writes going on (I'm guessing its mostly read, given the description) a single X25-M will make the DB go very fast regardless of random or sequential access. If the system is CPU bound, then getting a SSD like that won't help as much. But I'd be willing to bet that in a normal PC or workstation I/O is the limiting factor. Some tuning of work_mem and shared_buffers might help some too. Use some monitoring tools (PerfMon 'Physical Disk' stats on windows) to see if normal use is causing a lot of disk access. If so, and especially if its mostly reads, an Intel X-25M will make a huge difference. If there is lots of writes, an X-25E will do but its 40% the space for the same price. > > regards > > Mark > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance > -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
