Unrecoverable Read Errors (UREs) during RAID Rebuilds

[office politics]

I've never encontered a URE, but then again I haven't rebuilt many arrays. I remembered reading about UREs when SAS came out. It read something like they were unfavorable to use in server raid configs because of the limited amount of read or writes allowed.

This article may explain better. RAIDfail: Don't use RAID 5 on small arrays | Storage Bits | ZDNet.com

Big storage companies stopped recommending RAID 5 a couple of years ago. But I still see small 4-drive arrays touting RAID 5 for home and small office use.

Big mistake. You want to save money, but you also want to keep your data. RAID 5 isn't worth it.

but in these "hard, economic times" businesses want to keep IT budgets at a minimum.



How to protect yourself from RAID-related Unrecoverable Read Errors (UREs) | Servers and Storage | TechRepublic.com

If you are ever rebuilding a RAID system, Unrecoverable Read Error (URE) is one term you don't want to learn about the hard way. As the name implies, a URE makes for a really bad day, as it can stop a RAID rebuild in its track, essentially making the entire RAID volume unusable.

I won't go into a lot of detail about the “why” behind what causes a URE because many other very smart people have already done a good job of explaining it. (Admittedly, some of the warnings might be sensationalist, and there seems to be some confusion on terminology, but do your own math to see if you might have a serious problem.) What I will do is provide you with tips on how to make sure that you don't fall victim to these errors