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Disks in FC 60

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V. V. Ravi Kumar_1
Respected Contributor

Disks in FC 60

hi all,
We have an FC60 disk array. In that we have each 18GB disks in 28 slots. Now we want to extend the capacity by inserting more disks of 72GB each in remaining vacant slots.
I just wanted to know, is it allowed to insert a different capacity disks than existing disks?
Any suggestions are highly appreciated.
Thanks in advance
Best Regards
Never Say No
5 REPLIES
Bill McNAMARA_1
Honored Contributor

Re: Disks in FC 60

I don't have an answer off the top of my head, but this link may help:

http://h20000.www2.hp.com/bizsupport/TechSupport/Home.jsp?locale=en_US&prodTypeId=12169&prodSeriesId=33734

Later,
Bill
It works for me (tm)
Bill McNAMARA_1
Honored Contributor

Re: Disks in FC 60

Eugeny Brychkov
Honored Contributor
Solution

Re: Disks in FC 60

You can insert any supported disk, but you need to bind LUN using disks of same capacity: "Select disks of the same capacity. Binding a LUN using different size disks will result in unused capacity on the larger disks. For example, binding a 4-disk LUN that includes
two 9-Gbyte disks and two 18-Gbyte disks will result in a LUN with the capacity of four 9-Gbyte disks. Only 9 Gbytes of the larger disks will be used when creating the LUN" (cut from manual). If you wish to upgrade existing LUN with larger disks I believe the best way is to backup data, remove LUN, replace disks, create new larger LUN and restore
Eugeny
Brian M Rawlings
Honored Contributor

Re: Disks in FC 60

Different drive sizes are supported, but, as Eugeny points out, you should only bind like sizes into a LUN.

This raises a couple of things you should think about:
1> Any "hot spares" you have allocated need to be re-done, hot spares must be the largest drive size configured in the array (so they can fill in for any drive).
2> You really need to consider where the drives are you are binding together, for optimal availablility and performance. Ideally, you bind in vertical stripes to make I/Os to a LUN pass down all SCSI channels in the array, for maximum parallelism of the transfer.
3> You can add drives hot, and bind LUNs hot, but you can't add a drive chassis hot. Consider this as you add drives, in case you need to work some downtime into your plans.
4> You can't grow LUNs, they have to be unbound (data lost) and rebound in the new size. Plan carefully.
5> If you do have to unbind a LUN, it is much less painful if you can create the new larger LUN first, then mirror the LVOLs in the old LUN to their counterparts in the new LUN, then remove the originals of the mirrors (the original drives, then unbind the LUN. In this way, the data is available and on-line the whole time.
6> Binding LUNs takes time. You probably know that. But it takes twice as long with a disk twice as big... and you can only bind one LUN at a time (you can set up several bind operations, but they complete sequentially, not in parallel!!) The book is misleading about this -- we nearly died when we realized how long the whole bind operation was going to take for all 30 drives we had...

There's probably more to consider, but that's all I can think of for now. Hope it helps you do an end-run on the situation.

Regards, --bmr
We must indeed all hang together, or, most assuredly, we shall all hang separately. (Benjamin Franklin)
Brian M Rawlings
Honored Contributor

Re: Disks in FC 60

Actually, the "one at a time LUN binding" issue was allegedly going to be fixed in a FW release. I never saw it do other than one at a time, but I haven't seen that array in a couple of years...

The issue may be fixed by now.

--bmr
We must indeed all hang together, or, most assuredly, we shall all hang separately. (Benjamin Franklin)