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New mirror on Dell T610 H200 RAID

Posted on 2011-02-26
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Last Modified: 2012-05-11
I have a Dell T610 server with the onboard H200 RAID controller and running Windows SBS 2008.  The system presently has a single drive and I would like to add an identical drive and mirror it with RAID 1.  I would like to do this without losing the data on the existing drive.

I tried this before using the Dell Management console in Windows, but it erased the primary drive.

I am hoping that if I do this from the utility one accesses before booting Windows it will mirror without wiping the primary drive.  Does anyone have experience with this who can confirm whether or not it will erase the drive?

If I can't get a definitive answer, I'll just try the mirroring with some drives that don't matter and see if the primary one gets erased.  If it does, the only option I see is:

1) Make a good backup of the drive using Windows Server Backup
2) Test the backup by restoring to another drive to confirm that it works
3) Create the mirror
4) Restore to the mirror

Comments on the proposed procedure would also be welcome.
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Question by:CompProbSolv
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PowerEdgeTech earned 350 total points
ID: 34989205
Since the only way to configure a single drive on this controller is to use the non-RAID mode (basically unconfigured), then converting to RAID will destroy any data on the disk - as you have found out.  When in a RAID array, special meta-data is written to the disk - information about the array it is to be a part of.  In order to write this data on the disk, it must overwrite/erase what is on the disk.  On other, higher-end PERC's, the only way to use a single drive, is to set it up as a single-disk RAID 0, which would then be easy to convert to a two-disk RAID 1, but since you are not using one of those controllers, you will need to configure both drives in a RAID 1 before putting any data on it, as attempting to do so later will erase your data.  Your 4-step process is how you should go about this.
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by:CompProbSolv
ID: 34989247
Not the answer I wanted to hear, but reality is often like that!
Thanks for the info.
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by:PowerEdgeTech
ID: 34989270
I wish I could have given you better news ... maybe next time :)
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by:dlethe
dlethe earned 150 total points
ID: 34989310
It is a bit more ugly than even that.  The usable block count changes once you add the metadata.   So you are going to have to do a full backup & restore with software that lets you resize the partitions.

I suggest that you take the opportunity to attempt this using the replacement disk.

i.e,  do full backup.
take out original disk
put in the disk you want to mirror
restore
test.  If test fails, then you didn't risk your data, and you can figure out what went wrong and repeat until you get it right.  Then do it for real once you build a mirror via the controller.

You have one other option, and personally, I think it is a better option.

Just use windows native software mirroring.  It can be done online, and you don't need to reformat anything


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by:CompProbSolv
ID: 34990117
@dlethe

I should have waited longer and read your post!

I went ahead and started the procedure as described.  I did two full backups and then a restore to the spare drive.  All went well.

I put both drives in, created the RAID volume, it deleted everything, as expected.

I tried to do the restore and ran into the problem to which you alluded (error 0x80042407, disk too small).  I was unaware that Microsoft Server Backup wouldn't let you restore to a smaller drive.  Though these are the same drives, they show up as slightly smaller (as you suggested) when the metadata is added.

So..... I'm going with your suggestion.  I un-RAIDed the drives and am restoring to the first one.  When that is done, I'll do the mirroring in software.  Since the H200 doesn't really assist with the RAIDing, it shouldn't be a significant difference.

Had I known of the restore issue, I'd have saved a lot of my time today!  I guess that's the cost of education.

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by:dlethe
ID: 34990121
Well, it could have been worse ..  All you lost was time!
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by:dlethe
ID: 34990139
But I learned something too ... Bonehead Microsoft developers tell user AFTER the restore that the disk is too small?   Would it have killed them to test this BEFORE you attempted restore?  (I bet they already read the HDD capacity before it started because it must have displayed somewhere).    

if (NewDiskCapacity < BackupSize)
  BlowUp(ERR_INSUFFICIENTCAPACITY)

We're talking 2 whole lines of code.  Any developer who didn't think of this test has no business writing software.  They need a job where their true talent lies.  Rodeo Clown.

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by:CompProbSolv
ID: 34990182
At least in this case, it gave me the error right away.  I set up everything to do the restore and it took less than a minute to tell me that the disk was too small.  Are you suggesting that sometimes it gets to the end of the restore and THEN gives the error message?  If so, I will concur with the "Bonehead" comment.

I think there should be a serious warning when setting up the backup that it can only be restored to the same or larger hard drives.  If there was such a warning, I certainly missed it.
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by:dlethe
ID: 34990206
No, I interpreted your response as that it didn't tell you until the end.   Still it should check capacity, whether or not the source/destinations exist immediately
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by:CompProbSolv
ID: 34999371
PowerEdgeTech answered the question accurately and fully.  dlethe added some very valuable information (regarding the restore problem) that deserves some points.  Thanks to both of you!
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