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Raid 5, Lag

Last response: in Storage
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April 27, 2011 7:12:33 AM

Hi, i am running a 4 drive raid 5 on a LSI card. The setup is composed of WD green drives.

Now, after startup, regardless of time waited after everything is fully booted. The first time i access the array i get a 5-10 second wait time before it actually does anything.
Main OS drives are on raid 0 SSD setup, so that shouldnt attribute any lag to it.

The basically only happens the first time i access the array and is only a minor nuance. Was just wondering if anyone had any idea why?, or even if its somewhat common from spin up time and latency of the drives on a raid 5. As they didnt do that in jbod config.

Also note: all power saving features are off on the raid card.

Thanks for any help

More about : raid lag

April 27, 2011 8:24:08 AM

It sounds like your LSI card is spinning the disks down when their not in use to save power and wear / tear on the disks. When you go to access data on the disks the LSI controller must spin all of them up (if you listen you should probably hear the whirling sound) which typically takes from 3 to 10 seconds.

Most likely there is an option inside the LSI controller BIOS to control how this happens, otherwise you can use the Windows power settings to prevent "hard disk spin down".
April 27, 2011 11:01:37 AM

possibly, but my raid 0 disk array doesnt lag at all. And as stated the LSI power saving options are off. So its not supposed to spin the down. I did check windows however and that is off also.
a b G Storage
April 27, 2011 9:19:33 PM

The lad may cause be the WD green Drive, because it has IntelliPower feature.

Not 100% sure :-)
!