Disk upgrade in VMware ESX 3i

[amedinaj]

Hi all,

recently I replace the six 7.2K SATA drive in my PowerEdge server for six 15K SAS drives. Previously I made my VM's backup and then restored to the new RAID 50 volume. But when I start the virtual machine (centos 5) and run "dd if=/dev/zero of=testfile2 bs=8192 count=12207" the result almost the same I got with the SATA drives. My question is: VMWare ESX 3i inmediately recognize the new SAS drive? Or maybe it is writting the disk with the previous speed?

Thank you and best regards,

Amedina

[Jackobli · Accepted solution]

dd may not be the best tool for testing the performance. In theory, the SAS drives should you get more IOPs, dd does only write (sequential).

The RAID 50 with only six drives is not a really good choice either.

Depending on your RAID controller (Perc xx? with battery backed write cache??), the bottleneck is not disks but the controller itself (parity calculation on the two RAID5 and then striping on the RAID50).

Think about another RAID layout (8 disks RAID10?) and another test tool.

[amedinaj]

Hi Jackobli,

thank for your reply, I think i'm going out of topic, but one last question, you think a RAID10 can work better with my 6 disks?

[Jackobli]

you think a RAID10 can work better with my 6 disks?

It depends on your RAID Controller (there are different Perc Controller and they may have different Cache Size)! Is it powered by a Battery backed Write Cache? If not, I would suggest to buy one.

Most probably, RAID10 would work better, but I don't know, if the Perc can use six drives. Split 6 into 3 and build a mirror with 3 drives, uneven