Shared LVM (RAW Device)

[Hasan_9]

Hello,

I want to use Active/Active LVM RAW on two boxes? Is it possible? Does it require any special software?Please advice.

Hasan

[Victor Fridyev]

Hi,

Theoretically its possible and practically this is used in ORACLE RAC and GFS on RedHat4. You can see the same logical volume from more than one computer. You can read from it and write onto it from more than one computer. In the case of writing you have to provide some kind of locking, in order not to write to the same byte simultaneously from more than one source.

HTH

[Devender Khatana]

Hi,

As mentioned earlier it is quite possible to make one device visible and open by more than one node at a time but the OS is not capable of handling simultaneous writes to one file system and therefore only applications can use it.

Allthough there are no additional softwares required to achive this except your hardware should support this. Still only applications can make use of it effectively.

What is your requirement?

HTH,
Devender

[melvyn burnard · Accepted solution]

to do this on H-UX you would need SLVM which is only activated when you install and use Serviceguard Extensions for RAC with Oracle.
With the newer Serviceguard Storage Management Suite there are other option open including CFS .

[Hasan_9]

Letâ s talk about Oracle RAC as an example. I a familiar with it and will find my answer with this example. I read somewhere, We have to have ServiceGuard Extension for RAC, to activate SLVM (shared LVM). Now, I want to know If I plan to use a Shared LVM RAW for my project, it is activated or it is required something else, and What is SLVM exactly, that is a part of ServiceGuard Extension for RAC?

[Devender Khatana]

Hi,

Have a look at it
http://docs.hp.com/en/T1859-90017/index.html

HTH,
Devender

[Steven E. Protter]

Shalom Hasan,

If you create a shared LVM on shared storage and try and mount it from two machines at the same time, the results can be spectacular.

Your data can get corrupted and all kinds of bad things can happen.

In a standard serviceguard environment, the LVM management is managed with an active-passive model.

One machine is active and another is passive.

With Oracle RAC, it is supposed to be possible to with only the Serviceguard software(which is not shipped with the base OS) to mount in shared mode, and then Oracle RAC will let you open the oracle database from two nodes active-active.

If you were to try this with the standard oracle, the data would be corrupted.

So the real answer to your question is that you need Serviceguard to enable the mouting and you need special software from the application vendor to make sure the data does not become corrupt.

SEP