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Questions concerning SCSI drive array - mirroring, RAID 1?

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July 1, 2008 6:22:47 PM

I currently have a Dell PowerEdge 1600 SC server (2 x 2.4 GHz Xeon, 4 GB DDR, 2 x 73 GB mirrored Seagate 10k Ultra-320 SCSI drives) that I would like to add 2 more hard drives to. The new drives are exactly the same as the old ones, and I am hoping to set up the exact same configuration (have the new drives mirrored the same way as the old ones) to add a net 73 GB of storage.

The SCSI controller that I am using is an LSI Logic LSI21320-R. It has two channels (one of which is being used for the old drives), and supposedly possesses integrated data mirroring.

By the way, the drives and card are 68-pin.

To be honest, I have no idea how the first two drives were set up. It would seem that Dell OpenManage Array Manager was used to configure a RAID 1 setup for the two old drives (they appear as 1 virtual/2 physical drives in the Array Manager)...? Or does the card automatically configure a RAID 1 setup through its hardware? Is mirroring possible without RAID 1?

Anyway, I am just a bit confused as to what to do. The server is currently running an entire business, so it is critical that no mistakes are made - I need to get this right the first time.

Any input or advice is much appreciated.

Thanks!
July 1, 2008 7:16:29 PM

First, what do you use for backup? I like to use Bart PE with Acronis and create an image of the existing volumes to a USB hard drive (or somewhere safe) before anything like this is altered. But it seems you are asking the really important question, what sort of an array do you have now? Normally an array manager tells you this.

Also why is the purpose of adding the 2 additional drives? Do you just need more storage space? And what do you hope to have when you are done? 2 RAID 1 arrays, or a nesting of some sort?
July 1, 2008 7:43:42 PM

I have an Acomdata 500 GB external drive. It manages backup through a utility that came with it...

Right now I have a RAID 1 array (or so Dell Array Manager tells me).

I am just adding the drives to get more space on the server. I would just like to end up with 2 RAID 1 arrays (however, what do you think about RAID 10? is it worth it?). I have been reading about the bios options that LSI provides, and it sounds like I should be able to plug the new drives into the second channel, configure RAID 1 in the bios, and boot straight into Windows with a second drive.

Is it more complicated than this? Could I do something to potentially damage the old drives?
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July 2, 2008 3:45:12 PM

No its really no more complicated than you typed above. You could also just use a single channel of the controller if your cable will allow it. This might be an airflow consideration. Just add the 2 new drives create a RAID 1 array with them and reboot. (this should not change the boot order of the RAID controller but make sure the original RAID 1 array is set to boot in the controller bios)

Raid 10 is nice because its faster than RAID 1 and RAID 5 but does suffer a 50% overhead, but so does having 2 RAID 1 arrays. The other thing to consider would be keeping the OS and apps on the first RAID 1 and moving all DATA to the second RAID 1.

If you really wanted to get fancy you could do a RAID 10 and create a small partition like 30-40GB for OS and apps and then have a larger space for DATA. But this would require moving you existing DATA around so be careful.
July 2, 2008 6:23:04 PM

If I want to keep the existing data, can I simply configure RAID 1 on the new array, then RAID 1 + 0 the two mirrors?

Will it erase any data or cause any errors?

If it does work, what would happen on booting the server? Does the controller just stripe the existing data over the new mirror?

Thanks!
July 2, 2008 7:35:47 PM

Normally you would not be allowed to go from RAID 1 to RAID 10 without wiping the drives. Some controllers do offer the option to migrate data, most new controllers do this. This process is not on all controllers and can take an extremely long time when it the option is there. I dont know if your controller has that option. If not you would need to backup all data first and then setup the RAID 10 array. No matter what always backup before doing something like this.
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