VA7400

[Lacrosse]

Does the VA7400 have a snapshot feature like on the CLARiiON

[Eugeny Brychkov]

Yes, creating Business Copy LUN you're doing original's LUN snapshot. So instead of doing offline backup, you can create Business Copy LUN in seconds and then bring database back to production, and make backup in next hours. At the end you deactivate BC LUN and original LUN got updated with all data written before BC was created.
Please read BC manual for more info
Eugeny

[Lacrosse]

On the CLARiiON the snapshot only requires 20-40% of the primary image using pointer for the unchanged data the BCV requires same amount of storage like a mirror can can the VA7400 do a snapshot not requiring you carve out the same amount of space

[Fabrice Meynard]

Hello,

this is not possible on a VA7XXX array. You have to use BC functionality witch effectively reserved the same amount of space.

[Roger_22]

The VA has a non over-committing snapshot copy. Translated ??? only the blocks that change are copied, but you must reserve the space for the whole LUN to be copied.

Note that the VA uses a relatively small block size (246K). This typically provides better application performance during a snapshot operation by minimizing the data that must be copied during the 'copy on write' event.

Don't assume all snapshots are equal in performance and management.

[Brian M Rawlings]

Clariion "snapview" SW provides for either "point in time" snapshots (only changed data gets put in the snap volume, thus the 10%-20% figure), or for "clone" copies (complete 100% copy of the source volume, not instantaneous, takes minutes/hours to make copy).

If you heavily use a "snapshot" copy, you can impact performance of production access to its data, since you are often accessing the exact same spindle/blocks for both operations (for unchanged data). You can avoid this with a "clone", which can be put on its own spindles (big slow cheap drives, if desired).

This is important if you are doing other than keeping a "snapshot" in case you need to revert to it for some reason. Backups, Test/Dev work, report generation & data mining, these all can use the snapshot so heavily that production is impacted, and a "clone" would be better. Clones can also be split & then resynched, with only changed tracks updated, for much faster sync-ups.

By contrast, the HP VA arrays only have the snapshot capability, no full-copy "clone" is possible. One plus is that HP throws in (or used to throw in) the snapshot SW for free with an array, where EMC charges for it (and it's not cheap). Even for just doing a snapshot, the Clariion SW has more features and extra capabilities than the HP version, but, as I $aid, it co$ts. Lunch ain't free here either...

Hope it helps! --bmr