?The Crucial drive does not have power loss protection. The Samsung drive does. (The Crucial M550 has capacitors to protect data that's already been written to the device but not the entire cache. For instance, if data is read from the device during a garbage collection operation, the M550 will protect that data instead of introducing corruption of old data. This is listed as "power loss protection" on the spec sheet but it's not the level of protection that people on this list would expect from a drive) ________________________________ From: pgsql-performance-owner@xxxxxxxxxxxxxx <pgsql-performance-owner@xxxxxxxxxxxxxx> on behalf of Kaixi Luo <kaixiluo@xxxxxxxxx> Sent: Thursday, July 7, 2016 2:49 AM To: Mark Kirkwood Cc: pgsql-performance@xxxxxxxxxxxxxx Subject: Re: Tuning guidelines for server with 256GB of RAM and SSDs? It's a Crucial CT250MX200SSD1 and a Samsung MZ7LM480HCHP-00003. Regards, Kaixi On Thu, Jul 7, 2016 at 6:59 AM, Mark Kirkwood <mark.kirkwood@xxxxxxxxxxxxxxx<mailto:mark.kirkwood@xxxxxxxxxxxxxxx>> wrote: On 06/07/16 07:17, Mkrtchyan, Tigran wrote: Hi, We had a similar situation and the best performance was with 64MB background_bytes and 512 MB dirty_bytes. Tigran. On Jul 5, 2016 16:51, Kaixi Luo <kaixiluo@xxxxxxxxx<mailto:kaixiluo@xxxxxxxxx>> wrote: Here are my server specs: RAID1 - 2x480GB Samsung SSD with power loss protection (will be used to store the PostgreSQL database) RAID1 - 2x240GB Crucial SSD with power loss protection. (will be used to store PostgreSQL transactions logs) Can you tell the exact model numbers for the Samsung and Crucial SSD's? It typically matters! E.g I have some Crucial M550 that have capacitors and (originally) claimed to be power off safe, but with testing have been shown to be not really power off safe at all. I'd be dubious about Samsungs too. The Intel Datacenter range (S3700 and similar) are known to have power off safety that does work. regards Mark -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx<mailto:pgsql-performance@xxxxxxxxxxxxxx>) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
