Combining RAID levels on the same RAID card

Combining RAID levels on the same RAID card

Can I combine two RAID levels on the same channel of RAID card? Basically, I want to put my OS on RAID 1 and my database on RAID 5 from expansion point of view so I can extend my RAID 5 volume set in the future without hurting my OS. Is it feasible? Will it degrade RAID performance?

One more thing, I want to use two disks of 18.2GB, 10 KRPM for mirroring (RAID 1) and I have five 72GB, 10KRPM disks for my RAID 5 for the database. Could you please tell me if it will degrade the performance of RAID or not?


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There are a couple approaches, the first is to use a RAID card as you suggest and the second is to use volume management in the server over a standard HBA.

As to whether a RAID card supports multiple RAID levels concurrently, you need to check with the product specifications, although this seems like the sort of thing that might not be covered in product literature. A volume manager should not have any difficulty with this.

Without knowing any specifics on the application or the systems you are using, I wouldn't expect you to have performance problems putting RAID levels operating on the same channel. I assume you have Ultra SCSI 2 or 3. The drives you are using should give you reasonable performance for a medium sized database implementation. You might want to check the buffer size of your disk drives. Two MB buffers should be plenty.

Regards,
Marc

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This was first published in April 2003