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Low sequential throughput on DL360p Gen8 P420i 2GB Cache RAID5

 
01101001
Occasional Contributor

Low sequential throughput on DL360p Gen8 P420i 2GB Cache RAID5

I have a DL360p Gen8. It has a P420i controller with 2GB cache.

I have one Samsung 1TB SSD in the first drive bay working alone and 7 1TB Seagate ST91000640NS SATA drives in a RAID5.

I use Linux with this. There is one ext4 partition on the RAID, /dev/sdb1, and I have turned off journaling.

Using dd if=/dev/sdb1 of=/dev/null, I have measured raw disk sequential read speed of 650MB/s, which seems acceptable. I didn't measure the raw write speed because doing that might cause data corruption.

Using dd to do similar measurements but using files on the mounted /dev/sdb1, I got sequential read speed of 320MB/s and write of 160MB/s. This seems low to me compared to what a single disk alone can achieve, the RAID has 7 disks and I have 2GB cache.

So, any idea what I might need to do to increase the performance to say, 2 or 4 times of the current level?