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fracturing Clones flushing Host Buffers

Occasional Advisor

fracturing Clones flushing Host Buffers

I have a Clariion CX700 running Flare OS 02.19.700.5.030
The HP-UX 11.i OS is running
NAVIAGENT Navisphere Disk Array Management Tool (AGENT)
NAVICLI Navisphere Disk Array Management Tool (CLI)

I have an Oracle 9i database residing on mounted VXFS files systems. The file systems are defined on logical volumes which are created using HP's Logical Volume Manager (LVM). The LUNS used by LVM reside on the CX700 and are cloned.HP OnLineJFS is in use on the HP-UX server.

I want to backup the database by putting the database in backup mode, fracturing the Clones and backing up the clones on a secondary server.

I thought the File Systems whould have to be unmounted prior to fracturing the clones but EMC says in primus solution : emc70893

The key requirement for successively running clones is that host buffers are flushed so that all data resides on the source LUN (and thus on the clone LUN) before the fracture is initiated.

EMC is refering to the Buffer Cache and recommend multiple sync commands to insure the Buffer Cache gets flushed.

The question is what is the process for fracturing clones of file systems mounted on HP-UX 11.11 ?

Any problems encountered when restoring from clone fractures taken while the File System was mounted?

Thanks for your insight.

I'm going to start testing with the mount_vxfs -o mincache=direct -o convosync=direct parameters so the FS doesn't use the Buffer Cache.

Honored Contributor

Re: fracturing Clones flushing Host Buffers

Hello Dan,

I haven't ever run into problems with mounted file systems and fracturing the clones. At a very high level I do;

pre) Unmount cloned file systems and deactivate clone vgs
1) Start sync of the clones
2) Wait until the clones have been synchronized
3) Put database in hot backup mode
4) Verify clones are still synchronized
5) Fracture clones
6) Take database out of hot backup mode
7) Activate cloned vg's
8) fsck each cloned file system
9) Mount cloned file systems

As you can see I don't even do a 'sync'. By the time #4 finishes all the I/O has been flushed anyway. If you are really concerned or you are cloning file systems that don't get quieced by the database, there is a small package (can't remember the name) that can help with this step. Check the snap/clone documentation.