Migration from 7133-D40 (SSA) to DS4300 Disk

[desbo]

We are currently running two drawers of 7133 D40 disks which are (exact) mirrored by AIX draw to draw.

We have just set up our new DS4300 units and have several raid 10 configurations defined using the storage manage software.

We want to move all the data on the existing 7133s to the new DS4300 without renaming any logical volumes or filesystems. I know that we could do this using the cplv command but wondered if it would be possible to do it by setting up second mirror located on the DS4300 in AIX and just get the data to populate the new disks 'on the fly'.

When the complete system is running a second mirror we would then have to turn off mirroring but ensure somehow that the data remained intact on the new DS4300 disks.

Any suggestions?

 

[p5wizard]

If both drawers are fully populated and all the disks of the 2 drawers are in one standard VG, then that VG is already full (32 PVs max).

That would mean you cannot create a third mirror, but you can remove one of the SSA mirrors and recreate it on the DS4300 LUNs.


HTH,

p5wizard

 

[mag007]

So, you want to move from old SSA to DS4300? We can assume the LUN size on DS4300 is the same as disk size on SSA.

Why not just connect the DS4300, zone the LUNs, and import the new LUNs in the VG, and run a migratepv?

 

[desbo]

I have just read up on migratepv command and as it works by creating a mirror on the destination disks, resynchronizing then removing the data from the original disks, does that mean that I can do this live with the users still logged on?

Even if it is possible, is it safe enough to do it? I suppose it depends if I want to back the data up before migrating it.

 

[mag007]

Yes, you can do it while users are logged into the system.

It never hurts to have a backup copy; I think migratepv should suffice.

HTH

 

[desbo]

I have done some testing and am quite happy about using migratepv for most of my logical volumes and have seen that these migrations can be done with the users still on the system.

I am however very wary about migrating the logical volumes containing my Oracle database. My thinking at the moment is to migrate the Oracle PVs with the the users off and the database shut after a backup.

Am I being over cautious or will migratepv just work - guaranteed with the system running as normal?

 

[mag007]

It never hurts to schedule downtime, but 90% of the time you will be okay.

HTH

 

[p5wizard]

A migratepv (or mirror/unmirror which is basically the same thing) will work with any number of users online, but it will impact performance. I generally start that kind of work in the evening - friday evening is best - so that there are fewer users around to complain about loss of performance.

Also you could announce it to your user base, and tell them it is a necessary step to migrate the application/data to your new storage unit.

The data itself or access thereto will not be affected by the migration process.


HTH,

p5wizard

 

[desbo]

I have done some more testing. Firstly when trying to extend the vg by adding a DS4300 Disk Array made up of 6 x 73Gb disks defined as Raid 10, I hit a maximum PPs problem and had to change using 'chvg -t 4 xxxxxvg' which changed the maximum to 4064. Now when I try to extend the vg again I get this message-

0516-1163 extendvg: mtmsappvg already has maximum physical volumes. With the maximum number of physical partitions per physical volume being 4064, the maximum number of physical volumes for volume group mtmsappvg is 8.
0516-792 extendvg: Unable to extend volume group.

Is there any way of getting around this?


Also, what happens when I use the migratepv command on a logical volume that is mirrored (Raid 1) by AIX. What happens to the AIX mirroring after the lv is moved? Or should I turn off AIX mirroring before doing the migratepv?

 

[p5wizard]

See if you can define a smaller LUN on the DS box to present to the AIX server, so that you can go back to the previous "-t" factor.

Or remove one SSA copy (=mirror) if both are still good (sync'd), then reducevg half of the PVs (the ones you emptied by removing one SSA mirror) then you can extendvg the DS4k array disk into the VG and migrate (or mirror) the remaining SSA mirror to the new array (and in case you mirror - syncvg the VG).

Also, if you migrate 1 SSA mirror to DS4k, you keep mirroring between SSA and DS4k box, then afterwards, as the DS4k box is doing the mirroring for you, you can safely remove the remaining SSA mirror.


HTH,

p5wizard