And here's a URL of that short enough to not get truncated:
http://tinyurl.com/3orvcu
Also, here's my quick description:
An image is a full copy of a drive/volume/virtual machine file. If you
lose the original, you can use run off the image because it's a full
copy.
Snapshot is a virtual copy of a drive from a different point in time
than the current point in time. You can look at the snapshot, drag
files out of it, maybe even run off of it (if it allows read/write,
which they usually don't). BUT if you lose the original drive that the
snapshot is representing, the snapshot goes away too, as it references
the original drive. It is a virtual copy. Some vendors do use terms
like saying "full volume snapshot," which means an image. I think
that's like saying "physical virtual machine." It makes no sense. It's
either a full volume copy/image, or it's a snapshot. It can't be both.
CDP is a way of backing up a system. It continually (like asynchronous
replication) copies changed bits from one drive to another drive on
another host (maybe in another location). Unlike replication, though,
if something happens with your drive, you can roll it back to any point
in time because you have CDP. If you delete a file on a replicated
volume, for instance, that deletion will be replicated to the
replication volume. However, if you delete a file on a CDP-protected
volume, it will ALSO be replication, BUT a log of what happened is also
stored. That means you can say "take this CDP-protected volume back to
30 seconds ago before that idiot deleted the file." It will then undo
all writes to the volume since the last 30 seconds. Kinda cool.
A related idea is to use replication and occasional (usually hourly)
snapshots to get to "near-CDP." With TRUE CDP you can recover to any
point in time. With near-CDP, you can recover back to when you last
took a snapshot. That's why we call it "near-CDP."
-----Original Message-----
From: backups-bounces < at > backupcentral.com
[mailto:backups-bounces < at > backupcentral.com] On Behalf Of Henk
Sent: Thursday, December 18, 2008 9:03 AM
To: backups < at > backupcentral.com
Subject: [Backups] Backup: images, snapshots, CDP
Hi,
can somebody tell me the difference between images, snapshots and CDP?
Can snapshots restore the data when the original data is destroyed?
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