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I have a curious problem in that 1 (sometimes 2) drives do not get recognized in a RAID 5 set. The server is getting rather old at 5 to 6 years, but still seems to function well once the machine sees all drives. So that leaves me with three areas to consider: the motherboard, the SATA RAID card, or the individual hard drives themselves. I am leaning toward the RAID card, but have not had much dealings with RAID cards. What would cause individual drives not to be recognized in the set? If it was the card, I would think that it would be all or nothing. If it were a single drive, is it possible that it would only work sometimes? The only other thing to consider is that that they are different drives (Seagate and Western Digital) but all around 80 GB.

  • SATA RAID controller is 3ware Escalade 8506-4LP
  • Motherboard is a SuperMicro P4SPA+

Am open and available for more details if needed...

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Since it is 5-6 years old server, then the hard drive can be the cause too (hard drive can last 5 years but that's about the lifetime of them), First I will suggest do a backup of your data (or clone the data to another piece of hard drives), 2nd I would check SuperMicro website for BIOS Updates and also 3ware website for RAID controller firmware update, just make sure it is 5 years old server, if it is functional and upgrade failed then you must have a 2nd plan if it fails (if that is a working environment). but DO BACKUP of the hard drives, I think they might go bad!!! – Miro co Nov 15 '11 at 16:57
up vote 1 down vote accepted

Could be a failing hard drive.
Could be a failing backplane.
Could be a failing RAID controller.

The key word in all of the above: failing.
Start making backups (and verify that they're enough to rebuild your environment -- Do restore tests back onto bare metal or virtual machines!).

Miro co's advice on firmware updates, etc. is also a good idea, but make sure you have good backups first (I've lost RAID arrays to firmware updates before -- It's never pleasant to explain that one to the boss).
Also, if yo have diagnostic software for the server / RAID card now would be a good time to run it (Again, subject to having known good verified backups)

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