Logical Volume Manger - General Qs

[ianf]

Hi,

I'm a (semi) experienced solaris admin moving to HP-UX in a new job. I have used Sun's Solstice Disksuite a fair amount and have heard that HP-UX includes a version of Veritas Logical Volume Manager. I have only ever installed this package once and have never administered it. Could someone tell me:
1) if the LVM included in HP-UX is the same as the Veritas version that I have installed on a Sun system ?
2) if my experience of Disksuite will help me in administering LVM ?
3) any tricks of the trade in dealing with HP-UX LVM or easy traps to fall into/avoid ?

Many Thanks

 

[MikeLacey]

1) Yes. It's not precisely the same but HP, IBM use a version of OSF's Logical Volume Manager.

2) Sort of. I came the same route as you, Sun -> HP/IBM, and some of the disksuite concepts were useful. You will have to pay close attention to the LVM stuff though, it's not the same.

3) Not really, it's not trivial though. Mike
michael.j.lacey@ntlworld.com
Email welcome if you're in a hurry or something -- but post in tek-tips as well please, and I will post my reply here as well.

 

[Astur]

Hi ianf,

1) HP-UX 11i includes Veritas Volume Manager on the
application CD at no aditional cost (but is only a base
package. some features like mirroring require an aditional
product, also included in the app CD but at an extra cost).

2) I'm having the opposite route you and Mike have
followed (HP/IBM -> SUN, although I still more
involved with HP).I think the concepts are very similar,
so your experience with DS will help you, although the
commands, files , ... are very different.

3) I think LVM is easier than DS or VVM, mainly because
it has less features than those (it lacks RAID-5 support).
Mirroring requires an extra product.
Jose M. Blanco
MVP BrainBench for Unix admin.

 

[ianf]

Thanks,

So I guess what we're saying here is, "don't rest on your laurels". DS experience will help conceptually, but not technically, yes ?

OK, that's good info. I'll try and find tech manual then.

Cheers
Ian Ian

"IF" is not a word it's a way of life

 

[MikeLacey]

yep -- "DS experience will help conceptually, but not technically"

but I didn't mean anything so unfriendly as &quot;Don't rest on your laurels&quot; <smile> Mike
michael.j.lacey@ntlworld.com
Email welcome if you're in a hurry or something -- but post in tek-tips as well please, and I will post my reply here as well.

 

[bi]

I hope the following isn't t-o-o long winded:

I went from HP-UX and AIX to Sun. The hardest thing for me to comprehend when learning Sun and DiskSuite was that there are no volume groups in Sun as there are in the other two systems. So, with you going from Sun to HPUX, you will have to learn the roles and rules of volume groups and logical volumes.

One trap to avoid is HP-UX's SAM: It is buggy and it does not allow you to be precise on which disks you want to put logical volumes. (At least, the 10.20 version didn't allow you to be precise. I gave up on SAM and rarely use it now on my 11.0 system.)

You would be better off learning the command line steps to create and configure volume groups, logical volumes and filesystems. It helps if you have a script you can run on the system that gives you an understandable compilation of the output of the lvdisplay, pvdisplay and vgdisplay commands. (You usually need some information from each to create and configure filesystems.)

Another thing you may find hard to get used to is not being able to mirror your logical volumes unless you have HP's MirrorUX (a piece of software that costs extra -- HP is the only one of the three mentioned that makes you pay to have mirroring capability) and not being able to do RAID5 unless you have a non-standard I/O card. (AIX also requires special disks and I/O cards for RAID5.)

And finally, if you don't have Advanced OnLineJFS (again, a piece of software that costs extra -- HP is the only one of the three that requires a piece of software that allows you to extend filesystems while they are in use), you can't extend logical filesystems when they are mounted. You have to get your users out of the filesystems and unmount them before you can extend the filesystem after you have extended the logical volume.

Good luck!

 

[rjdscs]

A few tips that might avoid problems in the future. I look after a number of HP UX machines, all running LVM. They had been setup way before I took over so I had to deal with someone elses configurations. When the Volume groups were initially created on some of the machines little thought was given to the future so I hava some interesting problems to deal with.
1. When the Volume Group is first created the max number of physical extents on a physical volume is defined and cannot be changed later. On the Openmail machine I look after the max physical extents was set to limit the max size of hard disk to 9GB. Before I took over someone installed 2x18GB disk (the system is mirrored) but then found that only (GB could be used on each disk. At the end of last year the machine was running out of space, so I had to destroy the Volume Group and recreate it to utilize the 18GB disks fully. As this was a corporate email server of some 2000 users it had to be done over christmas when the system was not in use. Recreating the Volume Group was fine, but restoring all the email data took about 28 hrs.
2. When a volume group is initially setup the number of physical volumes in a volume group is defined, the default is 16. I have one machine that is running at >90% on one logical volume. I can't bring another disk in because there are already 16 in the volume group, so guess what, I will need to destroy the volume group an recreate it and then restore all the data. Again on a production machine.
So give some thought to volume group settings when you create them or you could be creating more work for yourself in the future