topic Is disk partitioning possible in XP-256 disk array? in Disk Enclosures

Is disk partitioning possible in XP-256 disk array?

radhakrishnan ravi — Tue, 15 Jul 2003 13:00:47 GMT

Hi,
We have an XP-256 disk array of 2TB comprising 7G, 14G, 21G, 35G disks catering to three HP9000 series servers running HP-UX 11.0, connected to the XP through Fiber channel.

As I was needing only a size of 2G for a volume group that would suffice for Oracle datafiles in raw logical volumes, I wanted the UNIX Admn to partition a 7G disk to avoid wasting of disk space. But I was told that the disk cannot be partitioned and a full disk of 7G has been given the size of the volume group. So a space of about 5G is being unutilised there. I cannot use the available space in the volume group for other datafiles as it will lead to performance issues.
This is the case for several other disks also.
How to avoid wasting of disk space? Is there a way to paritition, so that multiple volume groups can be created on the disk?

TIA
Radhakrishnan Ravi
Botswana Telecoms

Re: Is disk partitioning possible in XP-256 disk array?

Pete Randall — Tue, 15 Jul 2003 13:03:41 GMT

This is what LVM is for. You create a 2GB logical volume and use the raw device file to access it. The other 5GB can be used for something else.

Pete

Re: Is disk partitioning possible in XP-256 disk array?

Tim D Fulford — Tue, 15 Jul 2003 13:17:00 GMT

Hi

I thgought XP-256 used LUNs. If this is the case, simply create a 2GB LUN & use that. Other wise, use LVM to split it up.

Regards

Tim

Re: Is disk partitioning possible in XP-256 disk array?

Elena Leontieva — Tue, 15 Jul 2003 13:34:31 GMT

On our XP256 storage, several array groups are configured. Each group was formatted to produce a number of logical devices (LUNs). Each LUN presents the "unit" of storage to the UNIX server, and Unix servers have different number of LUNs, like 2,8,10, etc. LVM could be used on top of that if needed.

Elena.

Re: Is disk partitioning possible in XP-256 disk array?

radhakrishnan ravi — Tue, 15 Jul 2003 14:02:45 GMT

Thanx to all for the assistance.
I have just now heard from UNIX Admn that the smallest size of an 'unit' in the XP array is 7G and some other units are mulitples of 7G.
So it cannot be reduced to a size actually needed for the volume group.
I have also heard that the unit size should be uniform throughout the XP array and emulations like RAID4, RAID5 cannot be mixed together.
It seems we have to live up to wasting disk space forever when they cannot be allotted to different volume group sizes other than multiples.

Thanx
Ravi

Re: Is disk partitioning possible in XP-256 disk array?

Ian Dennison_1 — Tue, 15 Jul 2003 14:25:14 GMT

Ravi,

yes, you can split a 7 GB disk down into smaller portions on the XP512. Also, if you are short of space, you can use the left-over space on the Raid Packs and combine this space into 1 large virtual disk.

The feature that is used to split downm disks is called "VSC" (Volume Size Configuration). The steps involved are to literally "delete" the 7GB LUN definition, then recreate a smaller LUN from the space made available, and then assign that new LUN an LDEV number.

If you have not yet been on the XP Administrators course, I would recommend it before trying this, as you can really stuff things up if you are not careful.

Share and Enjoy! Ian

Re: Is disk partitioning possible in XP-256 disk array?

Angus Crome — Wed, 16 Jul 2003 04:25:13 GMT

Ravi,

Use LVM(lvcreate) to carve that volume up. It has very little overhead.
As for your performance issue, if you are worried about the performance of the disk, then it doesn't matter how (or where) it is carved up. Putting it in another Volume Group (not possible) would not make any difference. You will still be physically accessing the same disk. The performance of the XP-Series is generally very good, so I wouldn't worry too much about it.

Re: Is disk partitioning possible in XP-256 disk array?

Karthik S S — Wed, 16 Jul 2003 04:31:01 GMT

Hi,

It has been a long time since I worked on XP256. If I am remembering correctly XP256 has a feature to split the standard LDEVs ( 7GB and above) to smaller volumes. This is called CVS (Custom Volume Size). Pl. try this out.

Thanks
Karthik S S

Re: Is disk partitioning possible in XP-256 disk array?

Dave Wherry — Wed, 16 Jul 2003 13:13:43 GMT

Re: Is disk partitioning possible in XP-256 disk array?

Manuel_5 — Wed, 16 Jul 2003 22:20:10 GMT

Yes, witch Volumen size Configuration (VSC), is used to create smaller LDEVs from standar OPEN-3, OPEN,8, OPEN-9 and OPEN E volumes. The minimun size of a CVS LDEV is 35MB. CVs are easily recognizable from the ioscan on a hosts. Tehe entry will be marked with "CVS".

Manuel,

Re: Is disk partitioning possible in XP-256 disk array?

radhakrishnan ravi — Thu, 17 Jul 2003 08:22:53 GMT

Many thanks to all for the thought provoking clarifications given. The relevant UNIX support personnel maintaining our systems are being notified with the technicalities shared here. Due to ignoring the possibilities of reusing the space in smaller chunks in the LUNs, now a huge and precious amount of diskspace needs to be organised.

Thankyou all,
Radhakrishnan Ravi
Botswana Telecoms.