Very bad sas disks performance

[alexpt1]

Hi All

may be someone could help me!

i've setup esxi 4.1 build 260247 onto an Ibm x3200m3.

the system is equipped with a quad core cpu, 8 gb ram, Raid controller with 2 SAS 450gb 15k disks, the 2 disk are mirrored.

so, setup do not give problems, but the disks performarces are ridicolous! 0.16 gb/min during copies (i'm testing speed into several esxi1 using a 15gb vm file).

other servers equipped with sata disks give me 0,4gb/min during copy (not wonderful but...better)

ibm tell me to update firmware, done and same speed result.

so, i've booted the server with Knoppix 6, formatted disk, performed same filecopy: 5gb/min! so the problem come from esxi filesystem ?

anyone had experience like the mine ? may be anyone can suggest something to do ?

Thanks a lot to anyone will help me

Best Regards

Alessandro

[a_p_]

Operating systems like Windows and Linux do disk caching, ESX(i) does not. ESX(i) relies on the hardware, which means you need to attach BBU to your RAID controller. With the BBU attached you can configure the RAID/logical volumes to write-back mode.

André

[taylorb]

ALmost always this is going to be the cache on the RAID controller. Often if you do not have a Battery or Flash backed chip on the controller it will ship disabled by default. Often you can enable it, but without some cache backup method, you can get major disk corruption in the case of a power failure.

[alexpt1]

Thanks for your answer

If the problem it's the Raid controller setup, i'll have to had the same problem using both releases of esxi.

in fact when i boot with the usb key 4.0 i don't have problem, i/o speed it'ok.

when i boot with usb key 4.1 equipped the i/o problem appears.

But the hw it's the same! same disks, same controller,same datastore and same usb key ...

any suggetions?

thanks

Alessandro