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XP-512 Business Copy

Mr Reddy
Occasional Visitor

XP-512 Business Copy

We would like to copy from S-VOL to P-VOL. Does the system performs delta copy or is it a full reverse sync copy.
6 REPLIES
Ruslan
Respected Contributor

Re: XP-512 Business Copy

The following section provides an overview of P-Vol and S-Vol functions:

When creating volume pairs, data on the P-VOL is copied to the S-VOL to synchronize the volumes.

P-VOLs normally remain available to all hosts for read/write I/O, except during a reverse pair resync-restore operation.

Changes are copied from the S-VOL to the P-VOL during pair resync-restore.

S-VOLs become available for host write access only after the pair is suspended.
Read operations to the S-VOL are available except when reads are disabled with the paircreate command.

While the BC volume pair is suspended, all changes to the P-VOL and S-VOL are logged in a track-level bitmap.

Resync of the pair causes the S-VOL to be overwritten with the P-VOL version of any data that had been altered on either the P-VOL or S-VOL while the pair was suspended.
saju_2
Respected Contributor

Re: XP-512 Business Copy

Hi

We got a XP 1024 and we make a Business copy of DB with another set of disks (S-VOL). When there is any data corruption in P-VOL we used to do the reverse resync (copying data from S-VOL to P-VOL). This does not do a fresh pair create. What it does is a resync, ie it will compare the data in S-VOL and will copy it to P-VOL.

So the answer to your problem is that, S-VOL to P-VOl copy does a delta copy not a full reverse sync.

Regards
CS

Re: XP-512 Business Copy

Folks,

In BC, when you do a reverse sync, it does not actually copy the data from S-VOL to P-VOL. It switches the bits so that the S-VOL becomes P-VOL and P-VOL becomes S-VOL. All it takes is about 2 Secs to accomplish this.

Let me know if anyone has any questions in this regard ?
Thanks,
Bhanu

Re: XP-512 Business Copy

Also, on the same note, I would like you to be very considerate of what you are doing. I have seen people loosing their jobs over this. If in doubt, call HP to go over your written procedure to see if it looks good. It gets very complicated if multiple Arrays are involved and you have multiple HORCM instances running. Please make sure the right HORCM environment is exported before you do the reverse sync. I cannot stress it enough to double check the environment...like I said I have seen people getting fired over this.


Good Luck!!
Bhanu
Mr Reddy
Occasional Visitor

Re: XP-512 Business Copy

Thanks for clarifying that reverse copy from S-VOL to P-VOL is only delta. We need this capability as our DB size is around 1.5TB.

As per the documentation it takes few seconds only when you reverse the roles of volumes from S-VOL to P-VOL. But when you do the reverse resync I think it should take time as per the delta differences between volumes.

#pairresync -g -restore

This is used for reverse resync. Where in the differential data from SVOL is copied to PVOL(PVOL should be unmounted)

thanks & regards
Kishore Reddy
Mr Reddy
Occasional Visitor

Re: XP-512 Business Copy

Good feedback from the partipants.