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How much time to extend mirror volumes?

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Randy Hagedorn
Regular Advisor

How much time to extend mirror volumes?

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
10 REPLIES
Pete Devlin
Valued Contributor
Solution

Re: How much time to extend mirror volumes?

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
John Poff
Honored Contributor

Re: How much time to extend mirror volumes?

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
A. Clay Stephenson
Acclaimed Contributor

Re: How much time to extend mirror volumes?

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.
If it ain't broke, I can fix that.
Christopher McCray_1
Honored Contributor

Re: How much time to extend mirror volumes?

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
It wasn't me!!!!
S.K. Chan
Honored Contributor

Re: How much time to extend mirror volumes?

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.
Christopher McCray_1
Honored Contributor

Re: How much time to extend mirror volumes?

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
It wasn't me!!!!
Randy Hagedorn
Regular Advisor

Re: How much time to extend mirror volumes?

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
Christopher McCray_1
Honored Contributor

Re: How much time to extend mirror volumes?

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
It wasn't me!!!!
A. Clay Stephenson
Acclaimed Contributor

Re: How much time to extend mirror volumes?

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.
If it ain't broke, I can fix that.
S.K. Chan
Honored Contributor

Re: How much time to extend mirror volumes?

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.