topic Re: A3700 raid array in Disk Enclosures

A3700 raid array

alan swearingen — Thu, 30 Nov 2006 13:59:08 GMT

How do I increase the drive space in this unit. I have 8 9GB & 4 36GB drives in it already. I believe I can just replace the 9GB drives with 36GB drives. What other steps will I need to take?

Re: A3700 raid array

Steven E. Protter — Thu, 30 Nov 2006 14:11:29 GMT

Shalom,

1) Analyze the data on the system.
2) Back it up.
3) vgexport volume group.
4) replace disk with larger disk.
5) rebuild volume group and filesystems
6) restore data

This op requires downtime.

SEP

Re: A3700 raid array

alan swearingen — Thu, 30 Nov 2006 14:17:52 GMT

My question is how do I add the space to the raid array not to any specific volume group. I currently am low on unallocated space in the array and would like to increase the space to improve the systems performance.

Re: A3700 raid array

spex — Thu, 30 Nov 2006 14:36:22 GMT

Alan,

1) Backup all data stored on the 12H.
2) Pull one of the 9GB drives.
3) Wait for the array to rebuild to the active hot spare. This may take hours. Rebuild progress will be displayed on the LCD screen, or may be obtained via 'arraydsp'.
4) Insert one of the 36GB drives.
5) Wait for the array to balance.
6) Repeat steps (2) through (5) three times.

Note that to make all of their space available, drives must be installed in pairs. No downtime is required, although there will be a massive performance hit during rebuild operations. This effect can be lessened by decreasing the rebuild priority, although this will obviously cause the rebuild to take longer.

PCS

Re: A3700 raid array

A. Clay Stephenson — Thu, 30 Nov 2006 15:03:16 GMT

As indicated, it couldn't be simpler. Remove a 9GiB drive, insert a 36GiB drive, and wait for the light show to finish (possibly about 4-10 hours per drive) and then lather, rinse, repeat until all drives have been replaced. A big "gotcha" even with more available space is that you are still limited to a maximum of 8 LUN's.

Re: A3700 raid array

alan swearingen — Thu, 30 Nov 2006 16:20:52 GMT

Ok, this is what I was hoping was the answer. The only confusion is that the last two rsponses imply slightly different timing. When I pull the 9GB drive, can I install the 36GB drive right away or do I have to wait until the active hot spare rebuild is completed.

Re: A3700 raid array

spex — Thu, 30 Nov 2006 16:27:47 GMT

Alan,

You must wait for the array to rebuild before inserting the new drive.

PCS

Re: A3700 raid array

A. Clay Stephenson — Thu, 30 Nov 2006 16:38:35 GMT

Actually, you don't have to wait for the rebuild to complete. I just did a swap similar to this about two weeks ago. Remove the old drive. An error will be detected and then the rebuild will begin. It will show something like 30%, 50%, 70% --- and then the increments will be very small (and slow). You can insert the replacement drive while THIS rebuild is underway; the rebuild will pause, and then start again at 30% or so, and repeat the cycle. The golden rule is not to remove a 2nd drive until this rebuild cycle has completed. When the array has finished its rebuild, it will then start to balance. When this balance operation has finshed the array will revert to its normally rather quiescent state. At this point, you are ready to remove the 2nd small disk and replace it with the 2nd larger disk.

The good news is that the array can continue to do its normal work while this is going on. I have upgraded several 12H's from 9.1GiB drives to 36.4GiB drives while the arrays were quite active and running databases. It took 2 0r 3 days to complete the one at a time replacement but the databases never skipped a beat.

Re: A3700 raid array

spex — Thu, 30 Nov 2006 16:50:50 GMT

While it may be technically possible to insert a disk before the array finishes rebuilding to the active hot spare, it's not recommended.

I actually placed a call to HP storage the first time I had to replace a drive in a 12H. The technician made it patently clear that the rebuild was to finish before the replacement drive could be installed.

PCS

Re: A3700 raid array

A. Clay Stephenson — Thu, 30 Nov 2006 20:01:46 GMT

One of the very nice things about having rather extensive sandbox environments is that you can try things that might seem dangerous and then try them some more. As long as you simply remove the drive and insert the new drive in the same slot AND DO NO MORE CHANGES until the rebuild/balance finishes the rebuild will
work just fine. Of course, I'm not sure I would ever trust anything I got from some idiot (like me) on the internet or some idiot who works for HP. That's why I always do things first on my sandboxes.