Re: [Xen-devel] want to write a difference copy program to sync two VHDs in blktap

[R J <torushikeshj@xxxxxxxxx>]

Hello,

I tried to copy the VHD in two ways. One by using xe vm-copy command and other simple cp.
Im verifying the blocks with vhd-read command. VHD created by vm-copy has different BAT and BITMAP than the original one.

But with cp the BAT and BITMAP remains same as its a mirror copy.
Still no big improvements.

-- Rishi

On Sat, Aug 11, 2012 at 4:26 AM, R J <torushikeshj@xxxxxxxxx> wrote:

Hello List,

I'm using blktap on XCP 1.1 and developing a difference copy program for easy backup and remote archival.

The idea is to read the BAT of VHD1 and sync it to BAT of VHD2 with BITMAP and the data blocks.
Other way would be by adding a sha1 signature in each data block and comparing it with remote VHD.

I tried to get some info from below programs but could not get required info about adding a sha1 sign of data block while writing it.
Similar to ZFS this can be used to verify file integrity ?
May be if someone can guide me about how to inject data while writing it in data block of VHD.

Please advice.

-- Rishi

On Mon, Aug 6, 2012 at 9:26 PM, R J <torushikeshj@xxxxxxxxx> wrote:

Hello List,

I would like to know details of tapdisk-diff and tapdisk-stream
My aim is to find differences in two vhds and if possible sync them for redundancy via a difference-copy program

The idea is
- find the journel difference of src and dest VHD
- copy journel and modified blocks from src VHD to dest VHD for backup.

in my case both are nfs vhds.

Could anyone please provide me more info on above two programs ?

- Rishi

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