3ware 8506-4LP drive replacement problem

I have a server with a 3ware 8506-4LP RAID controller.  The original configuration was with 3 Maxtor DiamondMax Plus 9 SATA drives, labelled to be 120 GB.  (When installed, they each had a capacity of 122.94 GB.)

Recently one of the drives went out of service, and since they were about 5 years old it seemed perfectly reasonable that it was time.  I replaced the failed drive with a Seagate 500.10 GB ST3500413AS - and all was well for about a month.  Then, a second drive failed and I replaced it with what was supposedly the same Seagate drive, but in reality it was a different model number (ST500DM002-1BD142), but also rated at 500GB.  The new drive went out of service after only about a day of running, so I replaced it with another new Seagate 500GB drive.  It too runs for only a day or so, then goes out of service.

Thinking maybe the controller itself was actually failing, I bought a replacement controller, but the same thing happens with the new controller, so I have concluded that the Seagate disks for some reason are not suitable for this controller, even though it is rated to accept up to 1 TB drives.

I located some new Maxtor drives that were the same model number as the original, thinking that if I put exact replacements back in the array all would be well.  But the new drives, even though labelled the same as the original ones except for one or two codes, only register as being exactly 120 GB, and the controller won't accept them because they are smaller than the original drives.

My questions are:

1.  How did the original drives get formatted (?) so that they had MORE than the manufacturer's stated capacity? Can I do that to my new drives?

2.  Any thoughts on why one Seagate 500 GB drive is working OK but another model does not?

I am trying to avoid a disaster since I now only have two good drives in the array, and I don't seem to be able to find a drive that will work with this controller.  I have purchased yet another Seagate model drive, but I am accumulating a lot of *new* drives that don't work :)
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lita-pieAuthor Commented:
I have found out on my own how the drives have two different capacities even though the same model number - has to do with the LBA value when manufactured.  Apparently some were made with a higher capacity, and it is out of my control to change the capacity.  (122.94 vs 120 GB)

I have subsequently contacted the manufacturer of the controller and they have advised me what to do (replace all with same model drive.)  There does not seem to be a good answer for why the two drives of the same models are different capacities. Probably only Maxtor could answer that.

As an aside, I put the second of the original drives (which I thought had failed) back in the array, rebuilt, and it is going along just fine now.  I will obtain 3 new high quality drives and do as the controller manufacturer advised.
Greg HejlPrincipal ConsultantCommented:
So clone the drive

setup the 500GB drives as raid10 and clone the drive back onto the new array.

you're using raid 5 and you will lose your data if you don't do this quickly.

google "baarf"


make sure your seagate drives are 'ES' models don't use the consumer drives

western digital enterprise SATA drives are the 'black' series  

lita-pieAuthor Commented:
I was looking for answers that probably only the respective hardware manufacturers could answer - supposedly the controller should work with different drives, but I had problems.   Since I accepted my own solution, I gave it a "good" grade.
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