Hi, I need advice regarding RAID Controller configuration for PostgreSQL data. Known common best practices: - RAID cache at least 512MB - BBU is must have - cache mode = write back - disk write cache mode = disabled for hdd and low level ssd and disk write cache mode = enabled for ssd enterprise level with backup condenser - barrier=0 - vm.dirty_background_bytes=67108864 and vm.dirty_bytes=536870912 for RAID with 512MB cache.
But now I want to ask about special configuration for Dell PowerEdge RAID Controller (PERC) 9 series with 2Gb write cache due to Fastpath feature listed in Dell's documentation: > FastPathis a feature that improves application performance by delivering > high I/O per second (IOPs) for > the Solid State Drives (SSD). To enable FastPathon a virtual disk the Dell PowerEdge RAID Controller > (PERC) 9 series cache policies > need to be set to Write-Throughand No Read Ahead. This enables FastPathto > use the proper data path > through the controller based on command (read/write), IO size, and RAID > type. Using dell enterprise level SSD's in RAID 10 for PostgreSQL data is supposed. It seems that with this raid controller and ssd's the best practice would be slightly corrected: - cache mode = write through - disk write cache mode = disabled - barrier=0 - vm.dirty_background_bytes=16777216 and vm.dirty_bytes=134217728 Wouldn't this configuration be dangerous in case of power-loss disaster and especially isn't it dangerous to use barrier=0 with Write Through raid cache mode? Thanks in advance.
