shared file system between two servers

[Fadia Almarei]

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

[Ivan Ferreira · Accepted solution]

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.

[Fadia Almarei]

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.

[Ivan Ferreira]

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.

[Frantisek Kysela]

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

[Fadia Almarei]

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.

[Fadia Almarei]

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.

[Vincent Fleming]

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

[Uwe Zessin]

>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.

[Fadia Almarei]

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.

[Alzhy]

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.

[Fadia Almarei]

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

[Fadia Almarei]

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

[Alzhy]

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.

[Michael Duthie]

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

No add on products, best over gigabit.

MD

[Alzhy]

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..

[Michael Duthie]

"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.

[Michael Duthie]

Nelson,

Wanna cheap NAS .. try this

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

just set it up for home file sharing.

[Alzhy]

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.

[Michael Duthie]

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

[Fabian_Nowee]

It seems you are searching for a solution like ADIC, PolyServe, SanBolic etc...

[Fadia Almarei]

Dear All
I want more details in mounting the same file system in the two servers one with read write permissions and the other with read only more details in creating the volume group in both and how to mount the file system

[Michael Duthie]

Fadia,

you need to use NFS or CIFS, a volume cannot be mounted on 2 systems unless it is mounted read only on both systems.

see here

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=595019

I suggest #man nfs

NFS is easy to configure, free and supported for what you are trying to do.