Re: ibm flash copy, hp business copy

From: yls177 (yls177_at_hotmail.com)
Date: 06/10/04

  • Next message: Evgeniy Petrov: "remove command history" 
    Date: 9 Jun 2004 23:55:54 -0700

    dfreybur@yahoo.com (Doug Freyburger) wrote in message news:<7960d3ee.0406080727.42c9875a@posting.google.com>...
    > yls177 wrote:
    > >
    > > hi, basically, both of the above in the subject line achieves the same
    > > objective using 2 san disks storage for backup/restore. any insights
    > > to the pros and cons?
    >
    > IBM flash copy does a checkpoint of the current state into a copy.
    > As changes are made, new storage must be consumed in the original
    > to preserve that snapshot, or is it new blocks must be added to the
    > snapshot. Anyways, to have a full copy that does not effect the
    > new changing state, a mirror must be made. So flash copy is fast
    > to create but it still needs a full mirror if you intend to keep
    > it around for long. In particular a reverse copy might take a
    > very short time to restore state or it might be a full reverse
    > copy depending on the state when the reverse is done.
    >
    > HP business copy does a full mirror of the current state into a
    > copy. As changes are made to the original, the business copy
    > maintains a record of what blocks change. So a reverse copy
    > only needs to rewrite the map of changed blocks. Also the next
    > forward copy only needs to copy the changed blocks. Thus the
    > initial copy will take a long time, but if your data sees 10%
    > of its blocks change each day, subsequent syncs will take 10% as
    > long as the first.
    >
    > The business copy mirror does not consume new storage as changes
    > are made the way flash, but business copy requires the copy to
    > be 100% the size of the original. So your trade-off is known
    > storage requirements that are large vs unknown storage requirements
    > that might be small.

    but in either case, we still need the 2 same SAN storage available... isnt it?

  • Next message: Evgeniy Petrov: "remove command history"

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