Share a cooked file system managed by LVM...

[Tomas Martinez]

I need help/clarification. I have 2 64 bit Itanium boxes running 11i that are clustered. These boxes are attached to an EVA3K. I have several LUN presented to both nodes. All LUNs are managed by LVM. I need to create a LUN, for Oracle backups, which is a cooked filesystem but is shared by both servers. I am told this can not be done but I can't find any documentation says that it can't or conversly, explaining how to do it. Can someone tell me if, in fact, it is not support on this OS. If it is, how do I accomplish this. I am new to HP-UX. Please me know if I need to provide you with any more info. thanks in advance for any and all help, tomas

[Pedro Cirne]

Hi,

Is this a SG Cluster with Oracle RAC? Are you using raw devices?

Pedro

[generic_1]

First off I hope you are using securepath with this san.

I think what you are trying to do is present a disk to both systems so depending where your oracle instance is that you can use it for your backup. If you are doing serviceguard you could fail this filesystem back and forth with your database and this should work as it will only be active on one server at a time. If its not serviceguard you would have to have scripts that checked where your database was running at and fail it over. You can not run this filesysem write cable on two nodes at once.

[Devender Khatana]

Hi,

You are allready using service guard. You need to add another file system to service guard package running oracle & it will be automatically activated on the node where oracle will run. For adding file system to a cluster look at it

http://docs.hp.com/en/T1859-90017/ch02s04.html

Your LUNs on which you need to create this should be available on both the nodes.

HTH,
Devender

[A. Clay Stephenson]

Veritas makes a producr called something like cluster filesystem which can do this BUT otherwise the only way a cooked filesystem can be shared between nodes is that if ALL the nodes mount the filesystem read-only. The reason is quite simple -- buffer cache consistancy. Suppose node A writes to a file, the write takes place in buffer cache but nodeB doesn't know a thing about the contents of the nodeA's cache. Chaos will result in short order.

[Tomas Martinez]

Thank everyone for their responses!

Yes, we currently have Service Guard running on these boxes. But I am confused, Service Guard is for failover, right? I need /backup to be accessible by both nodes(shared).

Our DBA says the export/rman writes from both machines and we want to be able to have both nodes write to /backup at the same time. Apparently, they will not be writing to the same file so no locking for files is needed...if I undertstand it properly.

We currently have 2 LUNs, 1TB in size each, presented individually to both node 1 and node 2. So a total of 2TB. Oracle writes backup info to both nodes. But depending on where Oracle wants to right it, more might be placed on node 2 or node 1. Once all is done, the node that has had the majority of the data written to it needs close to 1TB. The other does not use more than 30% of it's 1TB.

So we figure if we can make one LUN, 1.5TB in size, have both nodes write to this LUN we can save the extra 500GB. This LUN needs to be a cooked filesystem for Oracle to write backups to it.

Sorry if I was not clear to begin with. Please any additional help would be greatly appreciated....tomas

[TwoProc · Accepted solution]

Tomas, You simply can't have a cooked file system shared by two servers unless you've bought Veritas' solution.

[A. Clay Stephenson]

Same answer as before. The only way that you can mount a filesystem on two hosts is read-only ON BOTH HOSTS; it doewsn't matter if only one will be writing at a time. The buffer caches will still be invalid. If you must do this then mount the filesystem RW on one host and then export the filesystem. The other system can NFS mount it rw as well but in that scenario only one host's buffer cache is in play so no corruption occurs.

[Dave Wherry]

While I would not suggest you do it for backups, as far as sharing a file system between 2 systems, you can use NFS.

[Simon Hargrave]

You would need a cluster-aware filesystem to do this, of which there is none available for hpux.

If you were using Linux you could use OCFS which supports rman.

And don't be tempted to "try" the /backup thing. It may look like it's working, but when you try and unmount/fsck/remount the filesystem it WILL fail.

[Tomas Martinez]

Thanks everyone for your help...tomas