PIT - point in time copy

Hi,

How does PIT works? For an example if I have source volume and target voume, how does PIT work? First it copies the data from source to target, and then monitor the changes and once there is a change, it copies the data?
mokkanAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

woolmilkporcCommented:
There are many implementations of PIT copy, such as "split mirror", "snapshot", "flash copy"  etc.

This is a Whitepaper from the 2002 Storage Conference outlining the common approaches and giving some insight into their functional principles:

http://www.storageconference.org/2002/papers/d05bp-aaz.pdf

"2002" seems a long time ago, but the basic concepts mentioned in the paper are still valid (and in use) nonetheless.

wmp
0
mokkanAuthor Commented:
Thank you, I read it but not getting the full concept. It is basically keep track of the changes  perdiatically?
0
woolmilkporcCommented:
It always keeps track of all changes, because every I/O must be intercepted.

Depending on the implementation changes are recorded in a flash area while the original keeps unchanged, or the changes are applied to the original while a "before image" of the original is copied to the flash area.
0
mokkanAuthor Commented:
For an example if the data  corrupted and if I want to decide the restore data, can I get pick a time?
0
woolmilkporcCommented:
Not with the mentioned flash/snapshot technologies.
You must decide whether to use the unchanged original originating from the time where the snapshot was initiated, or to use the updated copy.
Of course you can initiate several snapshots periodically, so you can decide which one is still good and which one is corrupted.

It seems what you're talking about is rather some kind of asynchronous (delayed) replication, where you can stop the replication in a certain time window once you noticed that corruption has occurred. You can then continue using the replica, which is still good given you actually hit the time window to stop the replication.
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Server Hardware

From novice to tech pro — start learning today.