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In a jam-- need serious advice re. RAID controllers


In a jam-- need serious advice re. RAID controllers

Help-- I made a huge mistake, and need some good sound advice.

We replaced a batch of legacy P4 3.0 GHz servers running old 7200 rpm SATA disks, with brand new DL160 G5 Quad-Xeon machines with the SC44Ge SAS controller and 300 GB SAS 15,000 rpm drives.

We expected these new boxes to be substantially faster: P4 vs. Quad-core Xeon, old SATA disks vs. new 15000 rpm SAS.

PROBLEM: The disk controller in each box is a SC44Ge, which I did not realize has NO cache.

Disk performance under load, even with our 15000 rpm 300 GB SAS disks is horrible, and users immediately started complaining loudly. These are terminal servers with interactive users, and the old P4 machines ran much faster because of disk caching. (disk-I/O intensive services)

I am considering swapping the SC44Ge controllers with the Smart Array P400/256MB and have a life-or-death (for my data) question.

There are 4 disks in each server. Disk 1-2 are setup as RAID-1 mirror, and Disk 3-4 are setup as a RAID-1 mirror.

1) If I pull the old controller and replace it with the P400/256, will the RAID volumes remain intact or will I lose all contents on the disks? Can the disks be moved from controller to controller like this?

2) Will the P400/256 with its onboard cache will perform much better than the SC44Ge? Is that a correct assumption?

Customers are screaming and we cannot go back to the old P4 servers, so any good advice will be VERY MUCH appreciated.
Jimmy Vance

Re: In a jam-- need serious advice re. RAID controllers

As a general rule you can usually move drives between Smart Array controllers.

Moving from the SC44Ge to a Smart Array will require a fresh install, or at least a fresh base OS install and restore data from backup

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Marcus Martin
Frequent Advisor

Re: In a jam-- need serious advice re. RAID controllers

As stated it should be ok. Your disks will be holding the raid information and not the card. when the new card is inserted it will pick up the disks and rebuild the raid information as appropriate.

At worst a rebuild of the OS will be required.

If you have mirrors try leaving the 2nd drive of each mirror out whilst installing the new card then at least you will have a backup of the orginal disk.

Good Luck

BOFH since 1999
Srinivas Suddapalli
Frequent Advisor

Re: In a jam-- need serious advice re. RAID controllers

Hi Jeffrey,

Although smartarray controller does support the drive swapping, its not recommended in your case.

Main reason behind this is due to drive conflict.

The P400 controller driver and SC44Ge controller driver are different. Though the RIS information is available on drives but the drives should find the compatible driver for controller connected to, so as to boot to OS without loosing information.

In your case, HP does not have any controller with cache and driver compatible to Sc44Ge, hence recommend you to backup data and reimage with new P400 controller.

Srinivas S