topic Re: SG without LVM? in Operating System - Linux

SG without LVM?

Informatikai Tanszekcso — Thu, 24 Feb 2005 05:32:53 GMT

Is it possible to mount "plain" partitions without using volume groups? Must I use volumes?

Krisztiá

Re: SG without LVM?

Simon Hargrave — Thu, 24 Feb 2005 05:38:51 GMT

You can use fdisk to partition a disk and mkfs the partition directly if you so choose. Just set the partition type to 83 (Linux) instead of 8e (Linux LVM).

Though using LVM does give you a lot more flexibility, I'm not sure why you'd want to use flat partitions?

Re: SG without LVM?

Informatikai Tanszekcso — Thu, 24 Feb 2005 05:45:19 GMT

In SG docs I see that packages mount volumes. Though LVM gives me flexibility, it is a potential source of error (adds to the complexity of the system).

Krisztian

Re: SG without LVM?

Steven E. Protter — Thu, 24 Feb 2005 06:59:57 GMT

My experience says you are better off with LVM. SG is designed to use and fail over shared LVM disk in volume groups as part of package failover.

SEP

Re: SG without LVM?

melvyn burnard — Tue, 01 Mar 2005 06:43:02 GMT

Whether you use file systems or raw disk, Serviceguard is looking to activate one or more Volume Groups for your package if these have been configured.
If you do not configure any Volume Groups then there is nothing to configure in the package to activate volume groups.
I suppose it is possible you could just have "plain" partitions if you wish, but this is unsupported.

Re: SG without LVM?

Ivajlo Yanakiev — Wed, 02 Mar 2005 08:49:03 GMT

Yes you can do it

1. You can use all disk as raw device without or with FS
2. You can use part of disk (fdisk) as raw device without or with FS

1 and 2 are not support from HP but work.

Re: SG without LVM?

Jean-Charles Ripault — Wed, 09 Mar 2005 12:52:44 GMT

Hi,

The point is not that LVM MUST be used. The point is that the different members of a cluster MUST IN NO CASE have one filesystem mounted simultaneously by two nodes. So, mounting and unmounting a filesystem is theorically sufficient.

However, activating and de-activating a VG gives it more security and flexibility.

Regards,

Re: SG without LVM?

Informatikai Tanszekcso — Wed, 09 Mar 2005 15:11:24 GMT

Does LVM prevent mounting simultaneously the same volume?

Thanks for your replies...

Re: SG without LVM?

Florian Heigl (new acc) — Wed, 09 Mar 2005 19:45:20 GMT

In the volume group header there usually is space for a 'vg in use' flag - this alone of course cannot be enough (i.e think of case when the last active member locks up) so You usually use an additional quorum device to ensure the failed node will immediately panic when it's partner took over already.

usually the active node has the vg activated read-write, and you periodically activate it ro on the second partner.
with OCFS You can also use the shared mode, but this filesystem lacks a few features according to the sourceforge page.

You should think of volume groups as something that makes Your work a lot easier, not the other way round - with MC/SG I'd almost always favor using Volume Groups for the shared storage. (Oracle 9/10 with ASM is another topic)
I do not know if Linux' LVM2 implements physical volume groups, too - if it does and You use mirrored storage these make things even easier.

There sure is a notable overhead as long as we're talking about 1 or 2 disks, but as soon as it's a few more, using a LVM will save You a lot of time.

Re: SG without LVM?

melvyn burnard — Thu, 10 Mar 2005 06:53:17 GMT

LVM in Linux does NOT have the exclusive mode activation.
It uses the standard vgchange -a y to activate all volume groups.
A request has been submitted ( or so I understand) to who/what/where in Linux world to have this functionality added, but as of right now I do not know whether this will be added, or if so, when

Re: SG without LVM?

Informatikai Tanszekcso — Thu, 02 Jun 2005 03:53:55 GMT

We are happy LVM users now, without any problems. I'm trying to minimize the number of modifications in SG scripts (though the number increases...)

Thanks for all the replies!

Krisztian