Fibre Channel and RAID Arrays

reptyle asks: "Anyone have useful experience with Fibre Channel RAID arrays? I deal with some Seagate Barracudas and one or another fails once in a while, but with no regularity. Before you ask: Yes, they are RAID5 compliant. The problem here is that I have trouble tracing the origin of the failure; it's not always the same hard drive; it's not necessarily the encasement or the adapter, and it's not clear what it is. But I suspect the particulars are less interesting than general collective testimonials of experience. I read that FC-AL is the kick-ass hot commodity, but I'm having problems seeing the performance boosts over the SCSI that were promised. I've read the FAQS, installed the latest firmware and drivers, and replaced individual hard drives, all to no avail. Any insights?"

Slow RAID 5 fibre? Check mode pages

[draziw]

Check the drive mode pages. Things that might need to be changed: Write Cache Enable (WCE) should be 1, Read Cache Disable (RCD) should be 0, read/write retries (even at zero, drives have hidden retries, and some drives just then use a default number) try 0 if you want for speed, but drives will fall out when they are really good, and number of cache segments (many drives default to 3, you might do better with 2.

Ryan

Re:Slow RAID 5 fibre? Check mode pages

[draziw]

If they are running fibre drives in a RAID 5 config, I figure they aren't a moron, and are running on a UPS.

Same problem here

[Lev_Arris]

>But I suspect the particulars are less interesting than general collective testimonials of experience.

Don't say that. We've got exactly the same problem here and we're still trying to figure out what's going on. At first we assumed that it was due to the enclosures. Then we suspected the cause to be power failures (because we found out that one side of the mirror was not connected to the UPS systems) I just read your posting and I find this very interesting because we happen to have Seagate Barracudas here too.

We'll keep investigating it.

Re:Slow RAID 5 fibre? Check mode pages

[draziw]

Ah - One more thing I forgot to mention. If it's ok to have the wait vs a drive failing; set your SCSI card, and the driver to allow at least 8 seconds for (recovered errors/Drive Command Timeouts). - That's how long these guys take to recover.