EVA Business Copy required space

[Charbel Bou-eid]

Hi,
I'm familiar with VA Business Copy but I want to switch to EVA 3000 and I'm not too sure that the BC EVA works the same as BC VA.
BC for VA requires the same amount of free space of a particular LUN in order to Business Copy'it. Does BC for EVA works the same?
Appreciate your quick replies.
Cheers,
Charbel

[Uwe Zessin]

Charbel,
BC EVA gives you 3 choices:

- Fully-allocated snapshot
This one reserves the same amount of storage like the parent virtual disk - just like the VA

- Demand-allocated snapshort (Vsnap)
This one does not reserve any storage within the disk group - it just grows as parts of the parent virtual disk get overwritten.

- Snapclone
This one starts like a snapshot, but the EVA is making a full copy in the background. Once this copy is complete you have a new virtual disk parent.


A Snapclone can be stored into another disk group - snapshots (at least currently) can not.

[Charbel Bou-eid]

Hi Uwe,

Many thanks for your reply.
Actually, after I have submitted my question, I found the datasheet on the HP web, but believe me the way you explained it is even better than the datasheet.

Now the other question is related to the Vsnap; as per the datasheet and your explanation, the Vsnap does not virtually reserve any space meaning that we can perform daily Vsnaps of a LUN.
1- Will the previous day Snap stops to grow if a new Vsnap is created?
2- Can I backup the Vsnaps and use as part of a recovery process? Is it a safe assumption?.

Thanks in advance,
Charbel

[Ricardo Rocha]

Hi Charbel

There some things you should know. You can create more than one Vsnap from the same parent Lun, but, in hpux, you can't present more than one Vsnap to the same host (believe me, I tried....). The Vsnaps are independent, so the existence of thesecond Vsnap will not affect the growth of the first one.

About the second question. You should not use your Vsnaps for recovery. If you have a huge problem in the EVA, you can also lose it. Vsnaps are mostly use for backup purposes, whitout needing of stopping databases. You must also be aware that the snapped database can be in a non-coherent state (Oracle). From my experience, there must be a good combination between the BC, Backup software and database.

Good luck,

Ricardo

[Charbel Bou-eid]

Hi Ricardo,

Thanks for this info.
But I still want to know if the Vsnap is one file containing like some kind of metada and algorithm know to the EVA or it is a space on the disk that I can normally mount and use on HP-UX?

BR,
Charbel

[Uwe Zessin]

Charbel,

a snapshot looks almost like another virtual disk except that it exists in the same disk family (I will attach a small picture to show you) and shares unchanged data with the parent virtual disk. You can present it to another HP-UX system and mount it there for backup to tape - by default, a snapshot is writable on the EVA. You cannot directly mount it on the same system, because the PVs will have the same meta data like those PVs of the parent virtual disk.

There was a similar discussion in one of the HP-UX groups and somebody claimed it was possible to alter the meta data of the snapshot PVs, so he could mount the snapshot on the same server, but it is not possible with the business copy framework that is running on the Storage Management Appliance.

[Charbel Bou-eid]

Hi Uwe,
Thanks for the additional infos, but my main concern is the Vsnaps and not the Snapshots as I'm kind of a familiar with VA Snapshots.
I need to know how can we get use oof the Vsnaps, can be back them to tapes, are they individual files containing some encrypted form of data used only by the BC software, can they be mounted on HP-UX.
Cheers,
Charbel

[Uwe Zessin · Accepted solution]

My apologies. I used 'snapshot' as a generic term.

The difference between a 'Fully-allocated snapshot' (like on the VA) and a 'Demand-allocated snapshot' (Vsnap) is only visible when managing the EVA. Both types can be presented to a host and appear as a copy of the parent virtual disk.