HP SAN Presentation to two nodes

Hi All,

I have a situation where I have a number of Virtual Disks connected to the same amount of physical servers. We're consolidating the number of servers and Virtual Disks; so I need to copy the data from one virtual disk to another.

I've done a copy from machine to machine; i.e. over the network; but wanted to know if it was possible to present two virtual disks to one server (i.e. the disk I'm migrating; present to the server I'm migrating it to) and do the copy to speed up the copy process. I'm looking at approx 2TB in total over 5 Virtual Disks.

I was interested in what ramifications this would have; i.e. the same virtual disk being presented to two hosts; one reading; one writing.

Cheers in advance.
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Pete LongConnect With a Mentor Technical ConsultantCommented:
Hello St3veMax,

Of course you can - how do you think VMWare Server moves storage about :)

Windows can get upset - if both OS's try and write to the disk at the same time - because WIndows can only support multiple machine access to sharwed storage in a clustered environment.

However to actually do it depends on your SAN on a MSA1000/1500 - you can use the Array configuration Utility on an attached Windows Server and enable the Storage to pre presented to multiple GLobal Identifyiers.
If its an MSA 2000 you do it from the web console

Selective Presentation MSA 1500

Management form a windows HP Server

1.      Launch ACU.
2.      If connected via Fiber you should see the MSA1500 listed on the controllers. (MSA1500 CS Controller in MSA1500).
3.      Select It.
4.      You should see all the arrays and volumes on the MSA, listed in the centre window.
5.      With "MSA1500 CS Controller in MSA1500" Selected in the centre window Click Selective Storage Presentation on the Right.
6.      In the new right hand window "Enable" should be selected > Click OK.
7.      Tick and un-tick the volumes as presentation is required > OK > OK
8.      Click Save.

MSA 2000

Web console

1.      Manage > Volume Management > Volume Mapping > Manage Host List.
2.      Add a simple name to the Nickname section next to each WWWName (i.e. ESX_HBA_1 or SWITCH_1 etc).
3.      Click "update".


>I was interested in what ramifications this would have; i.e. the same virtual disk being presented to two hosts; one reading; one writing.

Without a cluster filesystem you will get data corruption very quickly. The server that's supposedly just reading will do some writing, updating the last access time in the file metadata for example.
St3veMaxAuthor Commented:
Thanks Andy, This is what I thought re the corruption.

I should have said the SAN is a HP EVA4K; Do you know of any other way to copy the data from one virtual disk to another without using the network (i.e. force it over the 4gb fibre ?)

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andyalderConnect With a Mentor Commented:
If it is a single EVA you can buy business copy EVA which snapshots and snapclones which can then be presented to another host. A snapclone takes only seconds to be created and usable, it's then copied in background until it becomes a normal clone. ITB license is about £4,000, unlimited is just over £7,000. There might be a demo you can use. More details at http://h18000.www1.hp.com/products/quickspecs/11616_div/11616_div.html
Gerald ConnollyCommented:
If its an EVA, can't you just snap the source disk used on server A, and mount the snap on the destination machine - Server B, then on Server B read from the snap and write to the destination servers disk?
Yes, that's my understanding - we did it in the lab. But it's something like $10,000 for the licence that licenses you to use it.
Gerald ConnollyCommented:
Don't basic snapshots come for free?
Just checked with one of my colleagues, you can only make snapshots by using Business Copy EVA and you have to pay for that. There is a 30 or 60 day trial but the trial starts when you obtain the license for Command View EVA (i.e. when the EVA was installed) so it's only useful if the hardware has only just been installed.
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