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.
