Virtual copy vs physical copy

[kevgrn114]

3par 7400 version 3.2.1

Hi, new to the forum and 3par. So far I like the array alot. I am originally an EMC guy.

I have a client that is migrating to teh 3par from HP XP. currently they have business continnuance vols they use to do monthly test with. They put the DB in backup mode, let the synch catch up, then split it and do testing on teh test host.

I have told them that I can make an instant copy that is read writeable to the test host and just blow it away when they are done. The only issue they have with that is having to scan for a new lun on the test host. they would have to have their UNIX guys involved for that.. UGH

So my question is this.. In order for me to have the same lun presented to the test host, to avoid rescanning, and resynch the copy every month, which is the best way to go about this? If I make a physical copy with a virtual copy for later resynch, what is the time required for the resynch, or do I just export the virtual copy to the test host and it will be instantly available?

Thanks for any help on this!!

[JohnMH]

Take a look at the updatevv command Page 660 to resync an existing snap i.e it keeps the same id.

http://h20565.www2.hp.com/hpsc/doc/publ ... 03618134-3

There are two kinds of physical copy offline and online, you would need to use the offline method with resync -r option. This allows you to track all changes to the primary volume after the split and resync only the changes which get recorded in a intermediate snapshot. You can also set the priority of the initial copy using the -pri option, see same document page 158.

The same is discussed in this thread.
viewtopic.php?f=18&t=1087

However the snapshot method with updatevv as mentioned above would be the best way to manage this, with 3PAR's architecture physical copies offer little if any benefit over snapshots.

[kk2491]

Hi,

The Physical copy creation depends on the Size of the LUN and also the size of the data inside it.
I took a Physical copy of LUN size 100GB it took about 30min.
But resyncing of the Physical copy does not take much time since it considers after the previous sync.
And also the Physical copy takes the space as same as the base volume.

I believe this information is useful...

Regards,
KK

[kevgrn114]

Thanks for the info..
So, when I create a physical copy it is still just a point in time copy. In other words it wont stay almost synched with the source until a time when it can be split once the chances have cought up.
So we may have to rethink this whole thing..

Currently the BCV volume is kept in asynchronous mode. Once its time to test, the DB on the source lun is put in backup mode so no more changes are happening to teh source lun. Then the BCV lun catches up with the changes, usually in about 30 minutes for a 4TB db. Once it is caught up the BCV is split from teh source and the DB is put back into regular mode.

There doesnt appear to be any way to do this between two luns with the 3par on the same array.

Any thoughts? Its looking like we will have to put the DB inbackup mode, create a virtual copy, then present that virtual copy to teh test host as a new lun each time..

Hope all that makes sense..

[hdtvguy]

You do not have to create a virtual copy each time, you can refresh the virtual copy. I am not sure what platform you are using, but we used to do this with SQL on VMware using RDMs. We would power down the destination server, issue a updatevv command to refresh the virtual copy and power the VM back on. There are way to do it with running OSes that involve take the drive offline refresh the snap then bring the drive back online. Physical copies are not very beneficial on 3par unless you have true SLAs and have disk dedicated to different apps and such.

[kevgrn114]

That would be ideal.. I dont see an option to resynch a Virtual copy though.
Wen I right click on a VV I see:
Create Virtual Copy
Create Consistency Group Virtual Copies
Promote Virtual Copy
Create Batch Virtual copy.

[RitonLaBevue]

To resync a virtual copy use CLI : updatevv.

[kevgrn114]

AHH, ok thank you..

So now that tells me permission to perform updatevv on kevtestVC denied.

kevtestVC is a RW virtual copy of kevtest. the copy is not exported..

Are there CLI permissions I need to set up or do I need a certainoption specified?

looking at help i see options for -ro and -f both of which I tried and it says unrecognised option...

[JohnMH]

Same link page 342 CLI: setuseracl

http://h20565.www2.hp.com/hpsc/doc/publ ... 03618134-3

[kevgrn114]

Ah yes.. Ok. Cool. Thanks again for the help.. I'll go play some and see if I can get this thing going!