DIsk sharing: is it possible without MC/SG?

[Enrico Venturi]

Hello colleagues!
Ok, don't kill me if I had a new idea to save some moneys: I'd like to make a cluster without using MC/SG. Nevertheless I want to use the disk sharing, for instance by using VA 71xx.
My question is: can I "mount/dismount" the volume groups (or the LUN's) by the HP-UX commands? or by the VA SDM? In few words: without using service guard ...

thanks
bye

[Chuck J]

You might be able to achieve this using NFS

Chuck J

[John Palmer]

Yes you can. Serviceguard uses 'HP-UX commands' to do this sort of thing in any case.

As far as LVM is concerned, about the only thing that you can't do without Serviceguard is vgchange -a e i.e. activate a VG in exclusive mode.

Regards,
John

[Enrico Venturi]

Chuck,
I appreciated your reply but by using NFS it's needed a "master node" which mounts the disk and exports it to everyone.
If the master node fails (disaster) nobody is able to manage the disk and to export its data.

[Enrico Venturi]

John,
thanks for your advice: as far as I know vgchange itself is available just by using MC/SG. Did you mean that without MC/SG the command is still available even if without some option or it isn't available at all?
And in the second hypothesis, can I do everything without the vgchange?

[Justo Exposito]

Hi Enrico,

From the vgchange man page:
NAME
vgchange - set LVM volume group availability

SYNOPSIS
Activate volume group
/usr/sbin/vgchange -a availability [-l] [-p] [-q quorum] [-s] [-P
resync_daemon_count] [vg_name...]

Assign to high availability cluster and mark volume group sharable
/usr/sbin/vgchange -c cluster -S sharable vg_name

Remarks
MC/ServiceGuard cluster operations require the installation of the
optional MC/ServiceGuard software, which is not included in the
standard HP-UX operating system.

Lock Manager cluster operations require the installation MC/LockManager
software which is not included with the standard HP-UX operating
system.

Mirrored disk operations require the installation of the optional HP
MirrorDisk/UX software, which is not included in the standard HP-UX
operating system.

DESCRIPTION
The vgchange command with the -a option activates or deactivates one
or more volume groups.

Regards,

Justo.

[Enrico Venturi]

Justo,
so you mean that the vgchange is always available in the HP-UX ... none of its options are available just in MC/SG environment.
Therefore MC/SG isn't required.
Or not?

[John Palmer]

Without Servicegurad, the ability to activate a VG exclusively is not available. This means that there's nothing to prevent you activating a VG simultaneously on more than one server, mounting filesystems and cusing corruption.

A lot of what you pay for with Serviceguard is mechanisms to prevent this sort of thing from happening.

Regards,
John

[Justo Exposito · Accepted solution]

Hi Enrico,

Yes, This man page is from a box without MC/SG software installed.
$ whereis vgchange
vgchange: /usr/sbin/vgchange /sbin/vgchange /usr/share/man/man1m.Z/vgchange.1m
$ cd /usr/sbin
$ ll vgchange
-r-sr-xr-x 31 root sys 561152 Sep 9 17:10 vgchange

As you can see vgchange command exists in this box but you can not use some parameters if you don't have MC/SG installed.

This is the output in a box with MC/SG installed:
HP4 #> whereis vgchange
vgchange: /usr/sbin/vgchange /sbin/vgchange /usr/share/man/man1m.Z/vgchange.1m
HP4 #> ll /usr/sbin/vgchange
-r-sr-xr-x 31 root sys 569344 Oct 10 2000 /usr/sbin/vgchange

Hope this help you,

Justo.

[Enrico Venturi]

just another question, still related to the same topic: how can I list all the available volume groups?

thanks again.

[Justo Exposito]

Hi Enrico,

Try vgdisplay and check the line VG STATUS.

This is from my MC/SG box:
VG Name /dev/vg02
VG Write Access read/write
VG Status available, exclusive
Max LV 255
Cur LV 24
Open LV 24
Max PV 16

This is from the box without MC/SG:
VG Name /dev/vg02
VG Write Access read/write
VG Status available
Max LV 255
Cur LV 13
Open LV 13

Regards,

Justo.

[Justo Exposito]

Hi Again,

You can try this:
strings /etc/lvmtab
/dev/vg00
/dev/dsk/c1t2d0
/dev/dsk/c2t2d0
/dev/vg01
/dev/dsk/c4t8d0
/dev/dsk/c4t9d0
/dev/dsk/c4t10d0
/dev/dsk/c5t10d0
/dev/dsk/c4t11d0
/dev/vg02
/dev/dsk/c5t8d0
/dev/dsk/c5t9d0

Regards,

Justo.

[Enrico Venturi]

Justo,
I ask my company to refund you for the spent time!!

A lot of thanks.
Enrico

[Justo Exposito]

You are welcome Enrico.

Regards,

Justo.

[Vincent Farrugia]

Hello,

You will be able to mount disk groups in exclusive mode using VxVM instead of LVM. VxVM ALWAYS mounts disk groups (the equivalent of volume groups in LVM) in exclusive mode. But, VxVM is not free anyway, and since you wanted to make things cheap...

Vince