LVM and VxVM

Migrating data from two disk arrays to another single disk array.

 
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ccv
Occasional Contributor

Migrating data from two disk arrays to another single disk array.

OS: HPUX11.00
MIRROR UX: Not available
ONLINE JFS: Not available

Hi
With reference to above, I have data on several Filesystems which are mounted on LUNS carved from two disk arrays namely HP VA7100 and SUNSE3510. I have installed an Hitachi AMS200 and want to migrate data from both disk arrays to the Hitachi disk array.
Please provide me a safe way to migrate the data ensuring data safty, minimum application downtime.
8 REPLIES 8
Patrick Wallek
Honored Contributor

Re: Migrating data from two disk arrays to another single disk array.

Create LUNs on the new array, make sure they are visible to HP-UX.

Now add the new LUNs to the appropriate VGs, making sure that you have equal or greater space with the new LUNs as with the OLD.

Now use the 'pvmove' command to move the data from the old LUNs to the new LUNs. Check the pvmove man page for details on its usage.

pvmove actually uses a subset of mirroring to migrate the data, but you don't need the mirror/ux software installed to use it.

I have used pvmove fairly extensively in the past without any problems.

Just make sure that you don't do anything that would interrupt the pvmove while it is in progress. That can lead to issues getting your LV consistent again.

You might even be able to do this without having to stop applications.

Good luck.
ccv
Occasional Contributor

Re: Migrating data from two disk arrays to another single disk array.

Hi Patrick

Thanks a lot for the reply. I do not want to use pvmove because it has to be a continous process and our typical SAN environment may cause some issues while doing this.
cpio as I read in man page have some constraint of 2GB file limit and I hv several files bigger than 5-6 GB.
Also I want to create one new VG and put all the odd files systems which currently resides on different VGs to different lvols of the single new VG for the ease of admin.

Could you please help me to decide if I should use cp -r , fbackup/frestore, dd or else.
Steven Schweda
Honored Contributor
Solution

Re: Migrating data from two disk arrays to another single disk array.

For a possible reason not to use "cp -r", see

http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1203742

> OS: HPUX11.00

I don't know how bad HP's "tar" or "pax" is
on that OS version. For large files, I'd
expect fbackup+frestore or GNU "tar" to work.

A forum search for some keywords like
tar pipeline
should find several earlier related
discussions.
Pradep
Regular Advisor

Re: Migrating data from two disk arrays to another single disk array.

I believe dd would be the best size. i had used it to migrate data from VA to XP. works flawless.

syntax :

dd if=/dev/lvol/name of=/dev/lvol/name1 bs=2048k
Hein van den Heuvel
Honored Contributor

Re: Migrating data from two disk arrays to another single disk array.


>> Thanks a lot for the reply. I do not want to use pvmove because it has to be a continous process and our typical SAN environment may cause some issues while doing this.

I'm sorry but fail to understand this comment.
What kind of 'issues'? overheated bits?

The amount of work required for pvmove and dd is exactly the same. pvmove just ads a little feeling to the brute force work.
The main difference is that a dd MUST be done standalone while pvmove can be done online, as long as the volume is not activated shared.

IF, and only if, the volume is little used, then file based tools like cp, tar, cpio could have less data to move, but it is is more complex data and it may will be slower than blindly moving everything. And again it must be off-line as you would not want a file / directory to be changed after it was copied. fwiw, in my not terribly educated opionion tar has the best changes of creating an exact copy, followed closely by cpio, and cp -pR a distant third. (For example, file tools may 'expand' a sparse file).

>> Please provide me a safe way to migrate the data ensuring data safty, minimum application downtime.

You'll need to quantify volume of data the available downtime. Why not give 2 or 3 tools a try for a significant subset of the data, online, just as a test. Even though the data will not be valid, you'll then know what you are up against in time and effort. And more over, you'll have more confidence you can actually do it.

The only really safe and absolute minimum downtime solution is Mirror-ux (or similar tools if those exist). See if you can get it activated for a while? Trial or temporary license agreement?

Mirror-ux will allow ongoing application access and will leave you with consistent copy backup copy.

Judging by you mentioning "not available" on some potential solution I guess you googled around already. Look some more to be sure. Did you for example see:
http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1233744

Hope this helps some,
Hein van den Heuvel
HvdH Performance Consulting
Hein van den Heuvel
Honored Contributor

Re: Migrating data from two disk arrays to another single disk array.

forgot to add...
A downside of using 'dd' could be that the target Lvol's would have to be same as the source. That might needlessly cramp your style. Typically, when moving to new storage I find I like to take the opportunity to re-layout my logical volumes.

File based copies allow you to re-arrange everything, even splitting the data over multiple volumes if that somehow were deemed useful

Hein.
Patrick Wallek
Honored Contributor

Re: Migrating data from two disk arrays to another single disk array.

OK, I'm kind of confused now.

First you say that you want to migrate the data ensuring data safety and minimum application downtime. pvmove will do that.

Then you say that you don't want to use pvmove because "...it has to be a continous process and our typical SAN environment may cause some issues while doing this." How does your application stay up if you SAN environment has issues? It sounds to me as if you need to address the issues in your SAN environment before you move your data.

Most of the other methods mentioned will require some application downtime. pvmove could be be done without downtime.
ccv
Occasional Contributor

Re: Migrating data from two disk arrays to another single disk array.

Hi All

Very sorry about the vague comments posted by me on SAN env which resulted in confusion.
We are facing some SAN issues on random basis and working with vendors to eliminate them.

In addition to migration of data our new requiremant is to reacreate the VG/LV layout on the new Disk array so I got some sufficient amount of downtime also now.

The command "cp -r " may have some issues as pointed by Steven.

Found "dd" interesting option and tested it on a test server, but found that in addition to copy the data, "dd" matches the FS sizes also for both old and new LV. New LVs in my case will be greater in size than old LVs and do not want to extend new LVs after migration since this can be time consuming.

Found following fbackup command on itrc and tested it and found the results are as desired. Kindly let me know If there are any issues in using fbackup/recover or any considerations I hv to take care of.

cd /OLD && fbackup -i . -f - | ( cd /NEW && frecover -Xrf - )