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servers with SAN devices

Super Advisor

servers with SAN devices

Dear All

i have servers with tru64 version 4 they are connected to EMA12000 SAN , i have a device from the SAN mounted on one server , i want these device to be seen from another server and to create a domain on the second server to mount the file system of this device in case of faliure for the first server, how could ido this ,
kindly give me a detailed answers, that i do not have a good experiance n tru64.

BR;
Fadia Almarei
fadia.marei
13 REPLIES
Honored Contributor

Re: servers with SAN devices

hi,

you could do this but you might create yourself a load of other complications, for a start without some form of clustering or shared filesystem you risk data corruption if you do this while the original server is still up. even if you only did it when the first server was down it would be ok to introduce to the second server but if you rebooted the second server or had a crash you may find the new unit changes all your device numbering and screws up your current fstab entries. maybe just live with current situation.

fwiw



Super Advisor

Re: servers with SAN devices

is there any answer for my question or what ?
fadia.marei
Honored Contributor

Re: servers with SAN devices

Hi Fadia,

To make the SAN LUNs accessible to a different server, then you have to modify the relevant UNIT on the HSG80s and enable access to the other server.

This should enable to second server to see the disks, but be careful that both devices don't access the device at the same time or you WILL corrupt the data. Easiest to do this would be to disable access to the other server first with something like this:

hsg> SET DISABLE=ALL
hsg> SET ENABLE=


Once you can see the devices, you'll need to manually create a file domain, by creating a directory under /etc/fdmns and create a symbolic link to the relevant device.

This should then enable you to mount the file system as you require.

Hope this helps,

Regards,

Rob
Super Advisor

Re: servers with SAN devices

thanks Rob

i enable the device for all servers, but what is the exact command to create and make links for the dimain , exact command
fadia.marei
Honored Contributor

Re: servers with SAN devices

# hwmgr -view dev
(you will see what devices are created)
# hwmgr -scan scsi
(scan SCSI bus and find new device)
# hwmgr -view dev
(see what is the name of device, for example dsk77)
# mkdir /etc/fdmns/emadisk
(create directory for new advfs domain, for example emadisk)
# ln -s /dev/disk/dsk77c /etc/fdmns/emadisk/dsk77c
(Create symb. link for disk device for new domain. In this example it is just one partition. If this disk has more than one active partition, you need to create link for every partition)
# mount -t advfs emadisk#file_set_name /mount_point

Is everithing clear?
In vino veritas, in VMS cluster
Super Advisor

Re: servers with SAN devices

it is version 4 not 5
fadia.marei
Honored Contributor

Re: servers with SAN devices

Sorry, I did not see.
In version 4:
# scu show edt
(see current devices)
# scu scan edt
(scan bus)
# scu show edt
(check if new device is there)
# cd /dev
# ./MAKEDEV rzxy*
(where rzxy depends on bus-target-LUN)
Creatin of domain is the same, just replace device name.
If having problem with "# ./MAKEDEV rzxy*", send output of previous commands (i.e. scu show edt output before and after scu scan edt)
In vino veritas, in VMS cluster
Honored Contributor

Re: servers with SAN devices

Hi,

> i enable the device for all servers

Be *very* careful doing this. As mentioned previously, you will corrupt the file system if both servers manage to get hold of the LUN at the same time, and you're not using any clustering software.

The steps provided by Vladimir should be all you need to get things working, but please let us know if you need more assistance.

Cheers,

Rob
Super Advisor

Re: servers with SAN devices

so in version 4 their is no need to create the domains ?
fadia.marei
Honored Contributor

Re: servers with SAN devices

Hi,

You will still need to "create" the domain with something like:

# ln -s /dev/rzNc /etc/fdmns/emadisk/rzNc

(where N depends on the Bus-Target-Lun of the LUN), as Vladimir said previously.

Note that you shouldn't use mkfdmn as that will destroy the existing data.

Cheers,

Rob
Super Advisor

Re: servers with SAN devices

as this device will be shared between the two servers , so the name of the device will be the same on the two servers , is this right ?
fadia.marei
Honored Contributor

Re: servers with SAN devices

Hi,

That will depend on how the hardware is configured. If the FC HBA is in a different PCI slot, then it may be on a different bus, which will put it on a different device number.

You'd need to interrogate the output of

# scu show edt

to work out the correct rzN number.

Cheers,

Rob
HPE Pro

Re: servers with SAN devices

As others have noted, sharing the domain between two servers without clustering is fraught with risks.

If you don't want to cluster, why not just NFS export the filesystem from the first server to the second?

Martin
I work for HP
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