EVA 3-phase snapshot

[Max Sorokin]

Hi All,

Can somebody tell me a difference between traditional snapshot and 3-phase snapshot on EVA disk array.

Thanks, Max

[Vincent Fleming]

3-phase is a new feature of SnapClone, not Snapshot...

The non-3-phase snapclone allocates space wihtin the array on demand - as it is copying the data from the primary to the clone LUN. This tends to slow down the copy pace, and the copy takes longer.

The new 3-phase snapclone pre-allocates the space, then copies the data. The copy pace is muh higher, and subsequent copies have no need to perform the allocation again and again.

So, the 3-phase is more efficient and faster.

Regards,

Vince

[Peter Mattei · Accepted solution]

All

3-phase snapclone has been introduced quite a while ago with the EVA4/6/8000 and with VCS4.001 for the EVA3/5000.

Now, starting with XCS5.100 we introduced 3-phase snapshot for the EVA4/6/8000 too.

With standard snapshot when you initiate it it does the following:
1. create new container (kind of vdisks)
2. flush cache of the source vdisk
3. activate the snapshot

When you do not need the snapshot anymore you need to delete it. This takes some time due to deallocation of each and every segment.

With the new 3-phase snapshot you now divide the process in to 3 independent steps.

1. you create empty containers at any time

2. when you create the snapshot you just attach the vdisk to the container

3. when you do not need the snapshot anymore you can convert it to an empty container. This is done immediately!

Note that of course only fully allocated snaps can be taken that way!

Cheers
Peter

[Max Sorokin]

Thanks :)

[Peter Mattei]

Hello Max

No points ?? :-(

[Tom O'Toole]

Does anyone know where some (any?) documentation on this is??

How would one write an SSSU script to do these?

Thanks.

[Peter Mattei]

The principal is described here:
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00605855/c00605855.pdf

The latest SSSU manual can be found here:
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00605847/c00605847.pdf

Cheers
Peter