Обсуждение: Question about configuration and SSD
Hi,
do we need some special configuration for SSD drives, or is that enough to treat those drives normally?
regards
Szymon
On 02/06/11 16:26, Szymon Guz wrote: > Hi, > do we need some special configuration for SSD drives, or is that enough > to treat those drives normally? Make sure the SSDs have a supercapacitor or battery backup for their write cache. If they do not, then do not use them unless you can disable write caching completely (probably resulting in horrible performance), because you WILL get a corrupt database when power fails. If the SSDs have a supercap or a battery backed write cache so that they can guarantee that all cached data will be written out if the power goes down, you won't need any special configuration. You may want to tune differently for best performance, though - for example, reducing random_page_cost . -- Craig Ringer
> -----Original Message----- > From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Craig Ringer > Sent: Donnerstag, 2. Juni 2011 10:53 > > On 02/06/11 16:26, Szymon Guz wrote: > > Hi, > > do we need some special configuration for SSD drives, or is that enough > > to treat those drives normally? > > Make sure the SSDs have a supercapacitor or battery backup for their > write cache. If they do not, then do not use them unless you can disable > write caching completely (probably resulting in horrible performance), > because you WILL get a corrupt database when power fails. > ... Hello, may the database also get corrupt if SSDs are only used for temp tablespaces ? And will Postgres fall back on another temp tablespace if one get down? regards, Marc Mamin
On 02/06/11 18:53, Craig Ringer wrote: > On 02/06/11 16:26, Szymon Guz wrote: >> Hi, >> do we need some special configuration for SSD drives, or is that enough >> to treat those drives normally? > > Make sure the SSDs have a supercapacitor or battery backup for their > write cache. If they do not, then do not use them unless you can disable > write caching completely (probably resulting in horrible performance), > because you WILL get a corrupt database when power fails. > > If the SSDs have a supercap or a battery backed write cache so that they > can guarantee that all cached data will be written out if the power goes > down, you won't need any special configuration. You may want to tune > differently for best performance, though - for example, reducing > random_page_cost . Are you sure? SSDs support barriers and "fsync" just like regular hard drives, and your regular Linux filesystems will ensure things are committed to disk. Rather I would say - if you have an SSD *with* battery-or-capacitor-backed write-cache, then disable "Barriers" and enable writeback mode on your filesystem - and get a huge performance increase. But if you don't have those features, then just use your filesystem with the normal settings.. and it'll still be a lot faster than regular hard-drives, and just as safe. -Toby