XP24000 - present 1 x 300GB disk to OpenVMS, feasible ?

[TechM-VMS]

Hi,

Sorry, I am not storage savvy so my terminology and/or details may be laking but I need some guidence in terms of what is feasible and what is not in terms of volume creation on an XP24000 array

I look after an OpenVMS system and have recently requested 1 x 300GB volume to be presented to our system

At first the storage folk created 6 x 54 gb luns, which I cannot really do much with as I do not want to bind the volumes at the OpenVMS end because they will perform badly, I need a single 300GB volume presented to work on some large single files

After discussion , they agreed they could do it

Now, it appears they are going back on this agreement and are saying the biggest they can present are 2 x 150Gb volumes

I'm baffled here. We used to get volumes of this size created for us in another workplace on EMC frames all the time

So, what gives here ?

1. Is it a technical limitation with an XP array?

2. or is it just plain relucatance on the storage teams side?

3. or have they got a perfectly valid reason for wanting to refuse to create a single 300GB device and present it to our system?

Thought, ideas, insight greatly appreciated.

I'm not out for a burning session of the storage folk, if they have a legitimate reason then I'm all for following it but I can't really believe that 1 x 300GB single device cannot be created and presented

Thanks

[Torsten.]

There are many dependencies, specially if the disk groups are already provisioned, but ask them about concatenating.

[TechM-VMS]

If by provisioned you are meaning already exists and we are trying to expand / extend it?  then no, it is not already provisioned (i.e. existing)

This is sinmply a request to have a new volume created

If there is a technical limitation on the XP array then I'd like to know what it is :-) 

[Torsten.]

You most likely have the RAID level set at the disk group level (7+1 for example) and a number of LDEVs with a fixed size. In this case your storage team can combine a few of these ldevs for you. As said, it depends on a number of already made settings. Ask the team for the details, they should know about it.

[TechM-VMS]

ok

The response from them is...

That there is a technical issue with provding a single 300GB LDEV as there is no space to create a single LDEV of 300GB

They say that making an LUSE by concatenating LDEVS of 13GB will result in 24 LDEV in a single device and they believe this would be problmatic in the future

From my side, wether the device is presented as single unit or wether I am given smaller uits and have to bind them together on the server side still means the statistical rate of failure is identical

The problem is i cannot bind the volumes together, the system and current software is such that i need a single volume presented, how it is divied up on the storage side should not really be my concern

Anyhow, I was just wondering if this is a typical issue people face creating what I would think is a fairly small disk structure actually, I really didn't think 300GB would cause so much of an issue. Surely other systems are working with much much larger disk entities?

[Torsten.]

OK, they have no space left ...

>> They say that making an LUSE by concatenating LDEVS of 13GB will result in 24 LDEV in a single device and they believe this would be problmatic in the future

Not sure why this should be problematic.

This gives you the single device you want.

By the way, like almost any other array the XP cannot present a real disk to the outside world, it is always a LUN and in this case all the LUNs behind your single device are distributed across the disks in the diskgroup(s).