topic Re: How much time to extend mirror volumes? in Operating System - HP-UX

How much time to extend mirror volumes?

Randy Hagedorn — Thu, 17 Oct 2002 13:07:30 GMT

Hi Forum Community,

I am thinking about trying to squeeze in a mirrored logical volume extension during some non-peak production time.

I will be adding another 18GB Jamaica physical disk volume to an existing mirrored logical volume.

Does anyone roughly know if this process is a 5-minute process, 45-minute process or somewhere in between? I don't want to impact user 'too' long and maybe should be do this on non-production time.

Thanks,
Dewy

Re: How much time to extend mirror volumes?

Pete Devlin — Thu, 17 Oct 2002 13:09:23 GMT

Using the ol' 4 GB Jamaica's (preumably same speed as yours) I reckon to get 4GB mirrored every 15-20 mins. Depends how busy the machine is. But around 15-20 is what I us for the 7200rpm disks.
Cheers
Pete

Re: How much time to extend mirror volumes?

John Poff — Thu, 17 Oct 2002 13:10:04 GMT

Hi,

If you have OnlineJFS it should be pretty quick and easy, and you can do it while everything is up. You mention that you are adding one PV to an existing VG where the LV is mirrored. Will you be extending the current LV to the new PV and mirroring it to an existing PV? Just curious. It seems if you are doing mirroring you'd want to add two new PVs.

JP

Re: How much time to extend mirror volumes?

A. Clay Stephenson — Thu, 17 Oct 2002 13:13:12 GMT

I would estimate that the vgsync of 18GB would take something in the range of an hour but there's no need to do this in a maintenance window. I would feel perfectly safe hot-plugging a drive and doing the lvextends while normal operations continue.

Re: How much time to extend mirror volumes?

Christopher McCray_1 — Thu, 17 Oct 2002 13:14:26 GMT

Hello,

Judging by the size of you disks, I would chance to say, not long. It isn't the disk, perse, that is being mirrored, however, it is the lvols. With that being said, I have mirrored my 36Bb internals for vg00 and it didn't take long (about 30 mins) for about 19-2GB of filesystem space. I guess your only other issue is how hard are those disks hit in relation to I/O??? I usually do my mirroring during the day with little impact.

Hope this helps

Chris

Re: How much time to extend mirror volumes?

S.K. Chan — Thu, 17 Oct 2002 13:19:57 GMT

Extending an already mirrored logical volume is virtually a "non-impact" process. It's not like you're doing "vgsync" or "lvsync". If all you're going to do are ..
- installing the disk
- ioscan and diskinfo to make sure it's ok
- pvcreate it
- lvextend it
- check it (vgdisplay, lvdisplay, etc, etc)
then this should probably take about 30minutes, depending on how fast you can install the disk and how fast the system boots up. If I misunderstood your question, I'm sorry.

Re: How much time to extend mirror volumes?

Christopher McCray_1 — Thu, 17 Oct 2002 13:24:48 GMT

Sorry, I slightly misunderstood you question, but my basic answer is the same. It should be fairly Non-impact. The others have given good advise.

Chris

Re: How much time to extend mirror volumes?

Randy Hagedorn — Thu, 17 Oct 2002 13:34:05 GMT

Thanks for your replies,

To further clarify our intentions, we are actually adding two (a pair) of 18GB disks for extending mirrored logical volumes. One will be the primary and the other the mirror.

The reason I mention 'down time' is that this system is an ORACLE server and since we do not have JFS-online, we have had to have Oracle down to free-up the filesystem on these logical volumes.

Thanks again,
Dewy

Re: How much time to extend mirror volumes?

Christopher McCray_1 — Thu, 17 Oct 2002 13:39:17 GMT

Hello,

You can do the "preparatory work" up front.

Add the disks, pvcreate, vgextend and lvextend.

Then, when you get the chance to bring the db down, unmount and do you extendfs on them ( you can write a small script ahead of time).

And then, again, you can do the mirroring during the day as I stated, depending on your possible I/O issues.

Chris

Re: How much time to extend mirror volumes?

A. Clay Stephenson — Thu, 17 Oct 2002 13:41:45 GMT

I think that I would use this maintenance window to also add OnlineJFS. I would never run an Oracle box without it. The possible performance increases from using some of the online mount options and the the increase in uptime can easily pay for the cost of OnlineJFS. I never run a server without it.

Re: How much time to extend mirror volumes?

S.K. Chan — Thu, 17 Oct 2002 13:47:53 GMT

In that case the same argument still applies, now you got to take into account how long does it take for your database to shutdown and restart before and after the reboot. So it seems you'll be adding 2 disks to an existing volume group so that you got more extents, possibly you're adding them in different PVG (physical volume group) so that you get a "clean-mirror" since you mentioned one is primary and the other is secondary. Again from LVM side this is a quick operation. One more think you may want to check is have you hit the 16 max PV limit (ie the default) for the VG. If not you're ok.