Comments on: Dell PERC 5/i Not Caching

By: Paul M

Paul M — Thu, 25 Sep 2008 16:26:59 +0000

bonnie++ is a good test tool as it attempts to simulate real-world disk usage.

By: Joneyee

Joneyee — Fri, 04 Jan 2008 13:16:31 +0000

It has been my experience that data and config loss occurs most often in SCSI PERC controllers when an update to firmware or driver is performed when either one of the arrays is degraded or when a disk in the array has a sense key against it for predictive failure.

Backups are the key with RAID. RAID itself is not a backup option. It in essence buys time in the event of a physical disk failure. Additionally with SCSI signaling on a parallel bus, a bad signal from one drive can cause a failure in andother due to SCSI bus cross-talk.

SAS (PERC 5/6) in some way eliminates this problem as it is a point to point switch network architecture.

Turning writeback caching on is always an option that will increase read and write performance.

Loss of NVRAAM can be for several reasons. The metadata on the array itself can go bad due to poor array maintenance, lack of consistency checks, or turning patrol read off.

It can also be lost due to a failing CMOS.

“Yet somehow it lost it’s NVRAM settings of the containers, it then updated the second server in the Cluster to no containers. This resulted in a complete systems failure as no drives could be seen”

What kind of cluster, what was the config? Was it in an active/passive configuration? Was the storage unit set correctly in terms of bus settings?

I am just curious how one controlelr told another to dump configuration data.

By: A.

A. — Tue, 11 Sep 2007 16:49:30 +0000

omg, thats an interesting thing to know as i was planning to operate an large array on this controller. i guess this is going to change my mind…

By: David Palmer

David Palmer — Fri, 04 May 2007 05:48:17 +0000

A word of warning, I have a Dell Perc DC with twin external arrays each with 8 disks in a cluster that is supposed to switch over in event of a failure.

The Perc card did not fail, the only thing in the logs was some warnings about one drive that might fail, no orange lights, no errors on the controller.

Yet somehow it lost it’s NVRAM settings of the containers, it then updated the second server in the Cluster to no containers. This resulted in a complete systems failure as no drives could be seen.

We recreated the containers but windows could not see the volumes, we lost everything, the Windows cluster information, the SQL cluster, the data everything.

Dell said it was a firmware issue and suggested we contact a data recovery specialist who want $30k+ with no guarantees.

I do not know why these Perc controllers do not allow you to save the config to floppy or why they can’t properly log the problem.

I guess you have to keep the firmware updated but we have heard horror stories of those that did and lost their data.

Next time we are NOT trusting Dell with our data.

By: Jon Cavallo

Jon Cavallo — Thu, 29 Mar 2007 11:25:25 +0000

You should try http://www.iometer.org/