EVA 8000 Snapshot - novice question

[grahame lancaster]

Hi,

I am trying to understand EVA snapshots (as oppose to VMware snapshots).

If you have a LUN with a snapshot running and change the data on the 'orginal' disk by overwriting an existing file (say the orginal LUN is presented to a windows file server), what happens ?

1) does that change get written to the orginal disk and the data that is overwritten is copied to the snapshot

2) does the change get written to the snapshot and the orginal disk is left untouched ?

Can't get my head round the fact that the instant deletion of the snapshot on the EVA has no effect on the orginal disk, therefore I'm thinking taht it's no 1) thats correct ???

sorry If I'm being a bit slow..

[Greybeard · Accepted solution]

Hi, there are two types of snapshot. Fully allocated, this starts out the same size as the original and as the original is updated it's original data is placed in the snapshot kind of like an instant backup of any changed data. Demand allocated, this works in the same way but no need to allocate the whole capacity of the original as it will grow over time, better for a big LUN that only has changes to a few files.

[TarunJain]

Thanks Greybeard for explanation.

Grahame,
Long story short
You are right option 1 is correct

[grahame lancaster]

cheers guys, points awarded