RAID 1 disappeared on a Dell 2800, Perc 4e/Di

One more important item of note for performing the retag.

I would highly recommend that you offline one of the drives before leaving the controller BIOS. If the data was wiped on one of the drives then when they come online the controller will start matching the two drives. This will wipe the data on the other drive.

If the system comes up and the data is intact then rebuild the second drive into the array. If the drive is blank or the data is corrupt then go back into the controller BIOS and offline the drive. Online the other drive and check to see if the data is present on that one. If so then rebuild the other.

Thanks

Hello M

Yes, you are correct in your assumption that creating the RAID 1 again without initializing should get it back up and running. The PERC 4s can be very confusing because that is the time we were switching between SCSI and SAS/SATA, and also switching from Adaptec to LSI. The PERC 4/EDI is an LSI controller. To my knowledge you can do a retag with that controller. The major factor that decides whether or not you can do a retag is whether or not the controller forces and initialization upon array creation or scrubs more than just the array information upon deletion. I don't think the PERC 4 LSI controllers force an initialization or delete actual data during either of those processes.

One thing you could try before proceeding with a retag is to reseat the drive while the server is running. This will cause the controller to rescan the drive. If it finds the array information it should bring the RAID 1 online. Most likely it will be in a degraded state. Once you verify it is functional you can rebuild the second drive into the array.

If that does not work then you can proceed with the retag. The key to a successful retag is to match the settings. The member disks, RAID level, and stripe segment size need to match the previous configuration. The drives should be in their original slots as well. As you pointed out, be sure not to perform an initialization as that is a destructive process and will wipe the data.

If successful the retag will recreate the array data on the drives, and the controller will be able to see the data.

Thanks

Daniel,

Thank you very much for the information and the quick reply.. I have only one question and that is the tag. I am not quite sure I am up to par on this. By "tag" I think you mean the information that relates to drives, the parameters or entries.

One more thins, are these parameters for the TAG not automatically populated by default?

Again please excuse my ignorance. I am one that would rather be sure than assume and thereby cause an error that could have been avoided. And again thanks for the information and help.

I will be sure to be quite careful.

Manuel

By "tag" I think you mean the information that relates to drives, the parameters or entries. One more thins, are these parameters for the TAG not automatically populated by default?

Let me explain it a little better.

When you create a RAID array the controller writes metadata tags on each drive in the array. This metadata contains information about the array like stripe size, member disks, RAID level, array size, etc. When you choose to delete an array all the controller does is wipe out these tags. The actual data stays intact unless you perform some type of format/initialization/scrub of the drive. If you put the same metadata tags back on the drives then you will be able to access the actual data. If you change the metadata in any way, like a different stripe segment size, then the data will not be where it is expected. The controller will disregard the data and overwrite it. It will be considered corrupt at that point.

So in short, the tags are information stored on each hard disk that define the array characteristics. I hope that clears it up.

Thanks

Daniel,

I did take the precaution of storing the par maters (tags?) before I began my work.

Thankfully you mentioned to be cautious with the re-tagging of the array. Because when  I began to recover one of the parameters (tags?) was incorrect. Correcting the incorrect tag  per your note of caution and also taking one of the drives offline, again per your advice, I was able to recover the array.and begin moving some files that I had not moved previously..

Curiously powering up the server and then reseating one of the drives of the RAID 1 array did not cause the information to be read by the controller, any thoughts on this? Was there a specific time to insert, after CNTL+A or CNTL+M or perhaps I missed a detail? 

My original question has been answered. My sincerest thanks. I do have a question on growing the original array (RAID 1) with larger disks. Can I post on this or should I start a new post. Having looked through the forum. I believe that I understand that a RAID 1 cannot be grown, but that a RAID 5 can be grown to larger disks.

Daniel, again my thanks. I would not have thought to offline the drives without your note of caution.

Manuel .

Curiously powering up the server and then reseating one of the drives of the RAID 1 array did not cause the information to be read by the controller, any thoughts on this? Was there a specific time to insert, after CNTL+A or CNTL+M or perhaps I missed a detail?

No, it was just something to try. It will have the controller attempt to read the tags again. If they still weren't detected then the tags were gone or unreadable.

I do have a question on growing the original array (RAID 1) with larger disks.

The supported and recommended method is to backup, delete, recreate, reinstall, and restore from backup. You can resize the array with a retag though. To do this you will replace the drives one at a time with larger drive and allow them to rebuild. After the larger drives are built into the array you will delete and recreate the RAID 1. The only setting you will change is the space used. You will set it to use all available space. Be sure to take the same precautions as the previous retag, and make sure the rebuild completes before replacing the second drive.

Thanks