topic Re: can disks be shared ? in Operating System - Linux

can disks be shared ?

tom_422 — Thu, 23 Jun 2005 10:20:32 GMT

Can I share the disk array on my HP proliant with another proliant ? If so, what do I need to do that? I'm looking at running Oracle RAC on my two proliants, which is oracle running its processes on each box, but accessing the same database on shared disk. Do I have to buy a separate RAID box to do this ? Can I use firewire ? The proliants are DL380's with 6 disks, running Linux 3.
Thanks,
Tom

Re: can disks be shared ?

Steven E. Protter — Thu, 23 Jun 2005 10:45:07 GMT

Yes, disk arrays can be shared.

I do not believe firewire would be appropriate.

You can have two fiber/scsi connections to the disk array and then you can share the disks.

You can use LVM, or LVM and Serviceguard to handle the actual sharing.

What you can not do is have two systems mounting the same disk at the same time. That will under LVM at least work for about 10 seconds before your I/O subsystem goes wild.

SEP

Re: can disks be shared ?

tom_422 — Thu, 23 Jun 2005 12:03:18 GMT

Thanks for the reply. Since I want both machines to be able to mount the same disks, so each has access to the database files, I guess I need an external RAID box.

Re: can disks be shared ?

Uwe Zessin — Thu, 23 Jun 2005 13:22:21 GMT

Not only that - you also need a shared file system implementation! A SCSI or Fibre Channel storage array only provides access to blocks of data, but it has no idea what a file system is.

If you mount the file system on two plain servers, each one assumes it has full control over the volume. If you start creating and deleting files you will find out later that the file system has become corrupted, because the file system handler does not how to communicate with the other server(s) to synchronize metadata changes.

Re: can disks be shared ?

tom_422 — Thu, 23 Jun 2005 13:41:44 GMT

Right. I was planning on using Oracle's Cluster file system (OCFS) and ASM - Automated Storage Manager to handle the logical volumes.

Re: can disks be shared ?

Nils_9 — Fri, 01 Jul 2005 06:26:02 GMT

Hi,

I think there are at least 2 or 3 ways to share your disk with a network-based solution, but connecting directly your disk to both systems won't work, as Uwe described.

1st solution : on the first Proliant you can start NFS or Samba, which allow to create shares over a network. Then, mount the remote share on the local filesystem's second Proliant.

1st solution (bis) : invert the first and the second Proliants.

3rd (?) solution : use a third computer to share the data. Both Proliants will have to mount the shares.

But if you need read-write access, I don't know if it will be enough powerful. If one reads and the other writes, no problem.

Re: can disks be shared ?

Steven E. Protter — Fri, 01 Jul 2005 07:41:14 GMT

An external raid box is one solution.

I've actually build Samba/Raid boxes with very inexpensive hardware that can allow multiple servers to access resources.

For database acess, I'd put mysql or oracle on the same hardware as my little disk appliance.

You might want to email me using this webform. Use the text box to give details.

SEP
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