Allan Kamau wrote:
I am now thinking of investing in a SSD (Solid State Drive), and maybe choosing between "Crucial Technology 256GB Crucial M225 Series 2.5-Inch Solid State Drive (CT256M225)" and "Intel X25-M G2 (160GB) - Intel MLC".
Both of these are worthless for database applications if you care about your data. In order to perform well, SSDs need to have a write cache to buffer small writes. For PostgreSQL to work as intended, that write cache needs to be non-volatile. It is not in either of those drives. I hear tales of lost PostgreSQL data on Intel SSDs every month, the database is lucky to survive a single power outage.
The only relatively inexpensive SSD we've heard about on the Performance list that's survived all of the durability on crash tests thrown at it is the OCZ Vertex 2 Pro; see http://archives.postgresql.org/pgsql-performance/2010-07/msg00449.php for a summary. That avoids this problem by having an Ultracapacitor integrated with the drive, to allow orderly processing of the write cache if power is lost. There are other SSD devices that are similarly reliable, but the costs are quite a bit higher.
More background about this topic at http://wiki.postgresql.org/wiki/Reliable_Writes
-- Greg Smith 2ndQuadrant US greg@xxxxxxxxxxxxxxx Baltimore, MD PostgreSQL Training, Services and Support www.2ndQuadrant.us "PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
