Writing to a snapshot

[boomer_2]

Hi guys,
I have a storage EVA 4K with 8 vdisks for which i have created a snapshot....

Now i would ;like to know whether i can carry out writing on this snapshots i.e. i have presented this shots to my 2 new HP servers rx6600 and den created the same filesystem ehich i m using in productn ...
M acessing d same vdisks which r in prodn ...but thru snapshots...
I wuld like to test this new servers 2 dual core CPU and 16 GB RAM efficiency ...
IS IS SAFE FOR ME TO CARRY OUT THIS DRILL ????

And as to whether my ORIGINAL VDISK wnt get affected frm it ?????

[OFC_EDM]

These links may help you
http://bizsupport.austin.hp.com/bc/docs/support/SupportManual/c01077638/c01077638.pdf

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1071429

Start on pg 60 of presentation:
http://www.scribd.com/doc/2233504/EVA-Overview

I believe the whole point of a snapshot is to have an area which represents your primary data. But where you're free to read/write without affecting that primary data.

However I think a snapshot could potentially have performance impact against primary data. So is it safe? From a data integrity perspective...yes. But if you impact performance of production systems will your boss come running ? :)

I've never done a snapshot on EVA so I don't know if people experience performance issues. Its just a general comment on "snapshots" across vendors.

Whereas in very general terms a BCV (I'm thinking XP here) is a full copy and removes the performance impact.

Cheers

[OFC_EDM]

ftp://ftp.compaq.com/pub/products/storageworks/whitepapers/5982-9140EN.pdf

See page 16 Snapshot and Snapclone performance Management.

May help you decide if you should proceed base on performance impact against primary data.

[boomer_2]

Hi Kevin,
Those documents were really helpful to me ....

Just would like to confirm with u,

whatever i do on the snapshot will not affect my ORIGINAL VDISK RIGHT ???
apart from performance issue in production...which means i can carry out this test at night time....

[OFC_EDM]

It's my understanding that it won't affect the original data.

I'd suggest you re-post your question in the Storage forum.

There's some awfully good storage guru's there who could probably let you know about any exceptions to the rule :)

On my old EMC CX600 (gross) we did snapshots all the time specifically because it creates what I'll call a virtual copy to the DBA's that they could play with without touching the original data.

This had performance impact to those using production disk though. Because that style of snapshot Reads from the original disk. Then any "writes" to the snapshot aren't made on the original disk. They're tracked in memory/cache area.

I'm more familiar with the XP frames and less familiar with the EVA. But I believe the EVA have true "Snapshots" and "Full Copy" options...just named differently on the EVA.

Again I suggest posting in the Storage forum to get an answer from an EVA guru.

And make sure you have your data backed up to tape as well if possible.

Cheers

[boomer_2]

Ok Kevin,
Thanx for ur valuable suggestion......i will post the same quetn in storage forum...

[boomer_2]

Have postede d same quetn in storage forum nw under disk array...