"Supported" RAID 5

[lastmile77]

I've seen some reviews on newegg and posts elsewhere from people having issues running non-enterprise drives in RAID configurations. Supposedly Western Digital only supports the Raptors and RE2/3 drives in RAID configurations - according to some reviews. These have been in reference to more complex RAID configs, not 0 or 1. And its interesting that Seagate uses "desktop RAID" vs other phrases for some drives. Though they do use "RAID systems" with the 7200.11s vs "desktop RAID" with the 7200.12s which seems to follow the typical practice of selling older, more tested (maybe not more proven) hardware for business use. But at least they include it in the consumer drives and not just the ESs.

So, is this really an issue? The number of people with RAID setups using the consumer drives and not reporting problems seems much much higher than the number giving the kinds of reviews I'm referring to.

I'm not necessarily going to pay 2x as much for enterprise drives just to be safe. But if there are particular drive models that seem to have issues I'm sure we'd all like to hear about it. And drives just dying isn't the point of this thread unless something related made them kick the bucket.

 

[DonDon]

The issue you are going to run into with hard drives and RAID is the error recovery time.

All modern drives have error recovery built into the drive. The problem is, sometimes it can take a bit of time to recover from the error. During the recovery process the drive will not respond to the RAID controller. After a set amount of time, the RAID controller will declare the slow to respond drive as bad and drop it from the array. By the time a human becomes involved, the "BAD" drive has recovered from the error and will test fine. We are then left scratching our heads as to why the RAID controller declared the drive as bad.

To combat this problem, WD developed a feature called TLER, or Time Limited Error Recovery. What TLER does is limit the on board error recovery of the drive to 7 seconds. At that time, the drive will report back that it has a bad sector and the RAID controller will handle the error recovery. This will keep a drive that has an occasional error from being dropped from the array for no reason.

The caveat being that the RAID array must have error correction to recover from the error. RAID 5 and 6 do. Raid 0 does not.

I ran into this exact situation recently. I bought a Thecus N5200 Nas box. I bought 3 X WD GP 1 TB desktop drives to put in it. During the building of the RAID 5 array, 1 of the drives kept getting dropped from the array. When I tested the drive, it was fine. I ended up RMAing the drive to ZZF.

During the RMA process, I learned about TLER. When I got the replacement drive in, I turned TLER on for all 3 drives, and have not had a problem since.

You can read more about TLER here.

Don

 

[lastmile77]

Thanks for the explanation. That seems to fit the complaints I was reading. I should have been more specific since I had seen TLER on WD's site and had a clue that it was A problem but thought there were additional significant issues with using consumer drives.

After only seeing TLER mentioned on WDs enterprise class drives before my last post I was assuming it wasn't available on the consumer, desktop drives but that Wikipedia entry says otherwise. Seagate's name for their version and a description haven't caught my eye on their site yet but if I dig I'll find it.