On Mon, 3 Dec 2007, Martin Marques wrote:
Out of ignorance, do RAID devices have write cache? I'm talking about RAID through hardware.
Depends on the device. There are hardware RAID cards with cache, and ones without. Generally the ones with cache allow you to adjust whether the cache is used or not ("write-back"=used and "write-through"=unused). If you're using it, you should have a battery installed lest the system get interrupted while data is in the cache (and presumed written by the database) but not written to disk yet.
Some cards allow you to adjust whether the individual disks utilize their cache or not. For database use, if you're using the controller cache to preserve writes, you should make sure the individual disk caches are turned off.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
