RMS PTA
1 Copper

Re: H200 RAID 1 Predicted Failures

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I checked, but no gold - No logs for the RAID Controller, unfortunately.

But it's not like actual bad sectors can be migrated via synchronisation from one drive in the RAID array to the other drive, though, right? Yet if the one drive develops bad blocks and renders some files corrupt, it can synchronise those corrupt files over to the other drive in the array; is that right? Which is perhaps how the problem got started?

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theflash1932
6 Indium

Re: H200 RAID 1 Predicted Failures

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"But it's not like actual bad sectors can be migrated via synchronisation from one drive in the RAID array to the other drive, though, right?"

Right.  The controller will not copy sectors it knows to be bad from one disk to another during a rebuild, but as you said, 1) it may not know the data on that sector is bad and copy it, or 2) if it can't read it to copy it, it may not copy it at all, leaving a blank spot on the new drive - now matching the unreadable spot on the original - many controllers will abort the rebuild in this situation, or if there are a significant number of them.  When controllers do patrol reads and consistency checks, if it finds bad sectors or data on one drive that is corrupt/bad, it tries to correct it with the data on the other disk.  If it can't, that's when the controller knows there is a problem and alerts you.

 

RMS PTA
1 Copper

Re: H200 RAID 1 Predicted Failures

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For whatever reason, even though Dell said they would supply 2 new drives and a new controller, the technician that brought the parts only showed up with 1 drive + controller. So we kind of made the best of a bad situation by replacing the parts that he brought, deleting the RAID Array, recreating it, and restoring the server from a backup. So far everything still seems to be going fine - No additional predicted failures have been reported.

So is this kind of problem unique to RAID 1? Does it not defeat the purpose somewhat of having a RAID config when one drive failure can cripple the whole thing like this?

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theflash1932
6 Indium

Re: H200 RAID 1 Predicted Failures

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No, it is not unique to RAID 1, but it is more common ... it can also infect a RAID 5 or a RAID 10, etc.  The higher-end controllers (PERC 5/6, H7x0) are able to run Consistency Checks and Patrol Reads to pro-actively detect and repair problems like this ... well worth the extra $300-400 in my opinion.

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tqmbill
1 Copper

RE: H200 RAID 1 Predicted Failures

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Thanks to all who participated here. I have this identical problem with PERC H200 RAID1 and have been chasing my tail for months now: new disk, rebuild mirror and boom! "predicted failure." It's out of warranty so I've been on my own and this kind of help is invaluable. I found this reference that gives some great insight into "Double Faults and Punctured Arrays."

www.dell.com/.../EN

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