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Re : Autoraid 12H

Vincent_5
Super Advisor

Re : Autoraid 12H

Hi,
Can anyone tell me if I can add another two harddisk to my existing Autoraid 12h with size 18GB each. Existing there is 8 x 4GB running with one controller. And supposing if I want to add another controller, how can I load balance the Autoraid between all the disk ???
Please advice??

Regards
Vincent

nothing is better than to know more
5 REPLIES
A. Clay Stephenson
Acclaimed Contributor

Re: Re : Autoraid 12H

Yes, you can add 2 18GB disks to your existing array. Be advised that you will only add 18GB of usable space because the AutoRAID must maintain enough spare space to accomodate the failure of the largest drive. That "spare" space will be used as additional RAID 1/0 space so that it is not wasted. Insert the drives one at a time and the array will begin to load balance after about 30 seconds if "Auto Include" is enabled. This may take several hours. After the load balance is complete, repeat the process for the second disk.

There is absolutely no way to control how the disks are used or balanced; that is entirely automatic.

What you can do is split the i/o across both external SCSI buses; you should also try to limit the allocated space (LUN's) on the array to 50% or so. If you do that, the AutoRAID stores everything in RAID 1/0 rather that RAID5.
If it ain't broke, I can fix that.
Steven E. Protter
Exalted Contributor

Re: Re : Autoraid 12H

By default those 12H units are RAID 5. If you add another controller and more disks, the unit is supposed to stripe the data over more disks, providing a load balancing effect.

What I don't remember is whether thats a manual operation or not.

I'd back up all the data on that array prior to doing anything, especially switching disks from one controller to the next.

SEP
Steven E Protter
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A. Clay Stephenson
Acclaimed Contributor

Re: Re : Autoraid 12H

Believe it or not, you can add a second controller "on the fly" and not miss a beat. Of course, the safe method is to back everything up but I've certainly added controllers without incident.

I should add that you will see significanly better performance if you add 3 18GB disks rather than 2 and 4 disks would be better still. The more disks in an AutoRAID, the better it performs.

If yoy want the best possible performance from your AutoRAID, follow these steps:

1) Fully populate your array with disks.
2) Allocate as little space as possible as LUN's.
3) When creating a volume group, assign two LUN's of equal size to the VG. LUNA's primary path should be through Controller X (alternate Y) and LUNB's primary SCSI path should be through Controller Y (alternate X).
These controllers should be on separate SCSI buses.
4) Each LVOL in this VG should be striped across both LUN's --- typically in 64K chunks.

This method will allow you to fully utilize both external SCSI paths and all four internal SCSI paths.

You can also replace your 4GB disks with larger modules. As long as you do them "one at a time" and wait until the LOad Balance is complete there is no reason to shutdown.



If it ain't broke, I can fix that.
Jeroen Peereboom
Honored Contributor

Re: Re : Autoraid 12H

Vincent,

lots of information can be found at http://h20000.www2.hp.com/bizsupport/TechSupport/Home.jsp?locale=en_US&prodTypeId=12169&prodSeriesId=33733&prodSeriesName=hp+surestore+disk+array+12h

Check the User's and Service Manual. It will tell you something how it handles disks.

JP.



Ted Buis
Honored Contributor

Re: Re : Autoraid 12H

One controller means that there is not way to mirror the disk array controller's cache, so it by default will not report back, that a write is complete until it is fully written to the disks. The makes the cache usely for writes and really slows things down. I suggest you see if you can get a second controller.
Mom 6