I have a HP DL185 G6 Server (12 disk model) with the following spec:
- Quad Core Xeon 2.27GHz
- 6GB RAM
- HP P212 RAID controller with battery backup
- 2 x 128GB 15K SAS 3.5" (RAID-1 for the operating system)
- 4 x 750GB 7.5K SAS 3.5" (RAID-5 for the data, 2TB usable space)
The operating system is Ubuntu Server 9.10. Both drives have been formatted as EXT4.
We are finding that read speed of the RAID-5 array is poor. Disk test results below:
sudo hdparm -tT /dev/cciss/c0d1p1 /dev/cciss/c0d1p1: Timing cached reads: 15284 MB in 2.00 seconds = 7650.18 MB/sec Timing buffered disk reads: 74 MB in 3.02 seconds = 24.53 MB/sec
For info, the RAID-1 array performs as follows:
sudo hdparm -tT /dev/cciss/c0d0p1 /dev/cciss/c0d0p1: Timing cached reads: 15652 MB in 2.00 seconds = 7834.26 MB/sec Timing buffered disk reads: 492 MB in 3.01 seconds = 163.46 MB/sec
We thought this was because with no battery, read/write cache is disabled. We have bought and installed the battery backup and have used the HP bootable CD to change the cache settings to 50% read / 50% write and check cache is enabled on the drives and the controller.
Is there something I'm missing?