topic Re: shared file system between two servers in HPE EVA Storage

shared file system between two servers

Fadia Almarei — Fri, 03 Mar 2006 07:13:49 GMT

Dear ALL
I ave two HP-UX 11i servers i want to connect them to a SAN storage with a fiber cable,I have two questions

1-I want these two servers to see the same file system and to mount them at the same time (shared file system)what should I do in these two servers (I do not want to make them clustered)and what the application should i install in both.

2-if i use a redundant switch each server has two connections to the two switch and from this each switch to the storage,so from this each server will see the same HDD on the storage twice,what should i install or do in the HP-UX server to solve this problem.

thanks in advance,
Fadia

Re: shared file system between two servers

Ivan Ferreira — Fri, 03 Mar 2006 08:25:11 GMT

1- You can use Veritas Cluster File System (The file system must be clustered):

http://seer.support.veritas.com/docs/277359.htm

Or you can user RAW devices with Oracle RAC.

2- You need Secure Path, or simply use pvlinks, that is, add both disks to the same volume group. These are redundant paths.

Re: shared file system between two servers

Fadia Almarei — Fri, 03 Mar 2006 16:17:22 GMT

thanks ivan for your repliese,but i need more details for the two answers specially the second one, if you please give me more details.

Re: shared file system between two servers

Ivan Ferreira — Fri, 03 Mar 2006 16:54:25 GMT

1- To allow more then one node to write to the same filesystem, they need a method of control (locking) to coordinate the acces to the data. This is what a clustered file system provides. A clustered file system enables the access from two or more nodes to the same storage device, and performs the locking and access control.

If two nodes try to use the data without coordination, they will corrupt the filesystem.

The clustered filesystem does not provides server or service fault tolerance, it just allows the servers to use the same filesystem.

2- From the man page of vgcreate:

Using the PVLinks feature to create a volume group named /dev/vg00 with a physical volume that can be referenced by two different paths. /dev/dsk/c3t0d0 and /dev/dsk/c4t0d0 refer to the same physical volume, accessed via different controller hardware paths. In this example, /dev/dsk/c3t0d0 becomes the primary link to the physical volume. /dev/dsk/c4t0d0 becomes an alternate link to the physical volume.

vgcreate /dev/vg00 /dev/dsk/c3t0d0 /dev/dsk/c4t0d0

Pvlinks is part of HP-UX LVM.

Pvlinks are supported in active/active controllers configurations, like eva4k, eva6k and eva8k.

Re: shared file system between two servers

Frantisek Kysela — Sat, 04 Mar 2006 08:40:46 GMT

Hi,

1)
If you wouldn't use a clustered filesystem, you must ensure that only one server can mount this volume on read-write mode. The any other servers can mount this volume as red-only.

2)exactly as wrote a Ivan Ferreira you can use a PVlinks in active/active controllers configurations, like eva4k, eva6k and eva8k. If you use a EVA3k/%k you must upgrade firmware to version VCS 4.001 .

Frantisek

Re: shared file system between two servers

Fadia Almarei — Sat, 04 Mar 2006 12:15:01 GMT

Ivan
the volume group will contains two physical volumes so the size of it will be doubled although i use the same HDD am I right,or what.

Re: shared file system between two servers

Fadia Almarei — Sat, 04 Mar 2006 12:56:02 GMT

thanks Frantisek,from your reply i see that I can mount the file system on the two servers at the same time,and how to be sure to mount the same file system on both servers with different permition,
I want more details about Pvlinks what should I do on my HP-UX server to support it, and how to work in it.

Re: shared file system between two servers

Vincent Fleming — Sat, 04 Mar 2006 14:07:53 GMT

Last I heard, using LVM for a Clustered File System (Veritas) is unsupported - you MUST use the Veritas Cluster Volume Manager with the Veritas Cluster Filesysetm.

So, unless things have changed recently, I believe that you are required to have both products.

Good luck,

Vince

Re: shared file system between two servers

Uwe Zessin — Sat, 04 Mar 2006 14:17:13 GMT

>1)
> If you wouldn't use a clustered filesystem,
> you must ensure that only one server can
> mount this volume on read-write mode.
> The any other servers can mount this volume
> as red-only.

Sorry, but that is not safe, either. The reason is that the system which has read/write access will still cache data. The system which has mounted the disk read/only does its own (read) caching and most likely will not re-read the metadata, so it does not become aware of updates. This can lead to inconsistent views and even crashes, because the file system structure looks corrupted.

Re: shared file system between two servers

Fadia Almarei — Sat, 04 Mar 2006 15:10:42 GMT

so from where can i get these veritas products or download them,is they must be purchased or they have a license that ii must buy,kindly all these informations.

Re: shared file system between two servers

Alzhy — Sun, 05 Mar 2006 02:47:30 GMT

You can only do this in a Cluster Volume Manager (CVM) nf cluster environment -- either in a ServiceGuard or Veritas Cluster Server Environment.

You actually already have CVM software installed as part of VxVM/VxFS integration within HP-UX. You simply need to activate them via an installation of a license (a depot containing the license if purchased from HP or a license key if purchased from Symantec).

On 11.23 where VxVM 4.1 and VxFS 4.1 is available, CVM may already be integrated with MCOE / Serviceguard. On 11.11 - get hold of HP support.

Re: shared file system between two servers

Fadia Almarei — Sun, 05 Mar 2006 04:17:36 GMT

my systenm in HP-UX 11.11 and isee from swlist the following package
"Base-VXVM B.03.50.5 Base VERITAS Volume Manager Bundle 3.5 for HP-UX"
is it the veritas needed package

Re: shared file system between two servers

Fadia Almarei — Sun, 05 Mar 2006 06:03:09 GMT

Dear All
I almost get confused one of them told me to use Veritas cluster file system another told me to use veritas cluster volume manager,which product should i use related to my condition.
BR

Re: shared file system between two servers

Alzhy — Sun, 05 Mar 2006 21:13:17 GMT

You need to have MCOE (Mission Critical OE) to make use of CVM.. in short you need to have a ServiceGuard Cluster (or a Veritas Clutser)

The following is the 11th edition for 11.11 and above.

http://docs.hp.com/en/B3936-90079/ch01s01.html

http://docs.hp.com/en/B3936-90079/ch05s07.html

There is a 12th Edition for 11.23 Environments only.

Re: shared file system between two servers

Michael Duthie — Mon, 06 Mar 2006 09:27:38 GMT

If it isnt a clustered enviroment why dont you just use NFS.

No add on products, best over gigabit.

MD

Re: shared file system between two servers

Alzhy — Mon, 06 Mar 2006 09:34:13 GMT

Michael,

Very good suggestion indeed.! In fact in a previous client -- that is precisely what I've implemented. Due to the prohibitive cost of a cluster and certified NAS Filer (for an Oracle over NFS solution) --- we simply built our own NAS head - quad Gigabit ethernet and UDP protocol. Oracle performed just slightly below DAS/SAN storage but an elegant solution indeed.

However, Fadia might have a reson why he wants to have a truly cluster (shareable) filesystem using a SAN..

Re: shared file system between two servers

Michael Duthie — Mon, 06 Mar 2006 09:44:03 GMT

"Ivan
the volume group will contains two physical volumes so the size of it will be doubled although i use the same HDD am I right,or what."

Wrong .. LVM will recognize that both devices files belong to the same physical disk by reading the VGRA and add it as a PVlink rather than a new volume.

Re: shared file system between two servers

Michael Duthie — Mon, 06 Mar 2006 09:48:08 GMT

Nelson,

Wanna cheap NAS .. try this

http://www.freenas.org/index.php?lang=us

just set it up for home file sharing.

Re: shared file system between two servers

Alzhy — Mon, 06 Mar 2006 09:53:04 GMT

Michael,

Thanks for the tip.. but I've my own recipes.. for my NAS head OS, any stripped-down UNIX/Linux/FreeBSD is what I usually employ.

Re: shared file system between two servers

Michael Duthie — Mon, 06 Mar 2006 10:00:01 GMT

Yes I spend 2 days last week reinventing the FreeNAS wheel, should have searched google 1st.