Ask the Expert

RAID groups and parity groups

We use a HDS Thunder 9200 SAN configured at the back end with two RAID-1 groups (2 hard disks in each group). However, I can actually see three LUNs at the OS level. I don't quite understand, because I think each RAID group should be a LUN by itself. In this instance, one of the RAID groups obviously consists of two LUNs. Is that possible?

    Requires Free Membership to View

Yup. The Thunder 9200 supports the notion of parity groups and RAID groups. RAID groups can contain single or multiple parity groups. You can think of the RAID group as the actual RAID container for data protection, and the parity group as a partition of that container. This way, multiple LUNs can be created from each RAID group, and ported out to the same or different servers. This allows granularity in LUN sizes being obtained from the RAID group.

If each partition (parity group) is assigned to the same server, there should be no contention for the RAID group's disk resources. You can always just use the entire RAID group as a single parity group and create one big LUN.

This was first published in June 2005

There are Comments. Add yours.

 
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to: