I have a question about performance of the RAID controller Integrated RAID Module RMS25CB080
I have built RAID 5 array on 7 discs seagate Cheetah 15K.7 ST3300657SS
With settings (Write-back caching) it shows very good performance and with settings (Write-throught caching) it shows very poor performance on writing (twice worse).
RAID BIOS - Firmware Paskage Version 23.9.0-0018
HDD - Type: Cheetah 15K.7 ST3300657SS FW: 0008
RAID Cache Disabled:
Strip Size: 256k
Write Policy: Write Through
Read Policy: No Read Ahead
IO Policy: Direct IO
Disk Cache Policy: Disable
RAID Cache Enabled:
Strip Size: 256k
Write Policy: Write Back with BBU
Read Policy: Read Ahead
IO Policy: Direct IO
Disk Cache Policy: No Change
In case (RAID Cache disabled) write speed decreased in twice time(random and sequential). OS CentOS 6.3
I used FIO and simple copy (dd and cp).
The log files registered by IOStat and gnuplot built graphs by use this logs.
Graphs are attached.
G
Must it be this way or is it a bug?