lvmerge or lvremove - an LV from lvsplit ?

[Jerry Zhang]

Under HP-UX 11i, I split an LV from a mirror set. After backup, I want to remove it. Can I use lvremove, instead of lvmerge then lvreduce?

Thanks

[Sridhar Bhaskarla · Accepted solution]

Hi,

Use "lvremove" as it is no more part of mirroring. When you do lvsplit, it will seperate the mirror copies into two logical volumes.

lvmerge will sync up the extents again which may delay the process.

-Sri

[Patrick Wallek]

I don't know that I would want to try that. Once you split the LV, if you did an lvremove on the split copy, I don't know if you could remirror and then split the LV again.

Read the WARNING towards the end of the lvsplit man page.

[Jerry Zhang]

No. I don't care about re-mirroring. Just keep the original LV.

[A. Clay Stephenson]

Rather than doing an lvsplit to do backups, I suggest that you use OnlineJFS snapshot mounts. They will be much faster to create (only seconds) and you don't take the big i/o hit that is incurred when the LVOL mirrors are created. When you are finished with the backup, you simply unmount the snapshot and you are done.

[Jerry Zhang]

Thanks for mentioning the snapshot. The reason I did not use it because right after lvsplit, the original lV go back to production, Oracle has open database on it. I do not want to copy the database with anything open on it. That's why I used lvextend to create a mirror LV.

[James R. Ferguson]

Hi Jerry:

You note, "...right after lvsplit, the original LV go[es] back to production...I do not want to copy the database with anything open on it. That's why I used lvextend to create a mirror LV."

The concept of the snapshot is that when your backup is completed, the 'lvmerge' uses the bit-map of updated extents for synchronization. [See the man pages for 'lvsplit'] As Clay has noted, this would be faster than pure remirroring from scratch. After all, I presume that you want to do another backup the next day, again and again.

Regards!

...JRF...

[Jerry Zhang]

No, it is an one time deal.

[Jerry Zhang]

Thanks for all. I have removed the LUN using lvremove and everything is fine.