On Sun, Jul 17, 2011 at 7:30 PM, Craig Ringer <craig@xxxxxxxxxxxxxxxxxxxxx> wrote: > On 18/07/2011 9:43 AM, Andy wrote: >> Is BBU still needed with SSD? > > You *need* an SSD with a supercapacitor or on-board battery backup for its > cache. Otherwise you *will* lose data. > > Consumer SSDs are like a hard disk attached to a RAID controller with > write-back caching enabled and no BBU. In other words: designed to eat your > data. No you don't. Greg Smith pulled the power on a Intel 320 series drive without suffering any data loss thanks to the 6 regular old caps it has. Look for his post in a long thread titled "Intel SSDs that may not suck". >> In this case is BBU still needed? If I put 2 SSD in software RAID 1, would >> that be any slower than 2 SSD in HW RAID 1 with BBU? What are the pros and >> cons? What will perform better will vary greatly depending on the exact SSDs, rotating disks, RAID BBU controller and application. But certainly a couple of Intel 320s in RAID1 seem to be an inexpensive way of getting very good performance while maintaining reliability. -Dave -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
