snapshot

[David_492]

Dear ALL

in the EVA 3000 ARRAY what is the conept of the following ?

1. Snapshot
2. Snap clone
3. Local Replication
4. On line backup
Thank you all

[Christian Schwartz-Søre]

1)
A point in tíme copy of a volume. Data is not actually moved, but a reference point is kept in a map. A snapshot therefore doesn't take up any space, unless you make it "Space ineffecient" thus reserving space equal to the size of the original LUN. Space effecient only reserves space in the snapshot as the original data is changed and a copy-out is made to the snapshot prior to the change, thus leaving a true point in time copy of data(a snapshot).

2)
A clone is an exact copy of a LUN /volume, also a point in time copy. Here data is physically copied to a new LUN, a clone. This process is slower in creation than a snapshot.
A snapclone is a mix of the 2. Your clone is made available immediately, but is not fully created, as data is copied from the original LUN to the new LUN/snapclone. Once the copy process is done, a snapclone is completed.
It's made available immediately, and created in the background.
3)
Local replication is snapshot/snapclone technology.
Remote repolication is done using Continuous Access for EVA.
4)
You create a snapclone or snapshot, mount it on a backupserver, and do a backup of this copy of data. If you do it using a snapslone, no impact is done on your original data, as a snapclone has no physical relations to the original data.

Regards
christian