Problem solve Get help with specific problems with your technologies, process and projects.

Overhead for RAID 0+1 is too high ... should I use RAID-5?

I am in the process of migrating data from DASD to an enterprise-based SAN. This is one of several activities in a disaster recovery solution. A by-product of this is that I'll be left with lots of unused storage space from the legacy devices. I have a plan for these, but need some advice!

I plan to use two of the DASD (Sun 3310, 12 * 73 GB disks) to store replicated images of the boot disks from production...

machines. The idea here being that these can be used on the DR site to jumpstart a machine and have it quickly rebuild as a production machine, identical to how it was on the primary site before any disaster.

In terms of the storage devices, what is the best way to utilize the two 3310s? I have 24 disks, totaling around 1.7 TB of raw data. RAID 0+1 seems an option, but the overhead of this just seems obscene. How best can I utilize these 24 disks?

In terms of I/O performance, writing is not a primary consideration, but reading of data needs to be at a decent enough rate to not cause a bottleneck when jumpstarting clients. I also need to consider the fact that the units I have inherited are JBOD and do not have a hardware RAID controller.

I would definitely use RAID-5 in this situation. It has good read performance, and makes much more efficient use of the disks. I would not use them unprotected (they WILL fail!) and certainly would not waste half my space on 0+1! The 3310 can have dual SCSI busses, so RAID-1 might seem logical, but RAID-5 is the way to go. Don't make the RAID sets too large, and keep a hot spare or two in case of a disk failure. Maybe make two five-disk RAID-5 sets per 3310 and keep two disks per system in reserve. That would leave you with just over one TB of usable space, or 33% overhead.

Read Brett Cooper's answer to this question.

This was last published in December 2004

Dig Deeper on Data storage management

Have a question for an expert?

Please add a title for your question

Get answers from a TechTarget expert on whatever's puzzling you.

You will be able to add details on the next page.

Start the conversation

Send me notifications when other members comment.

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

Please create a username to comment.