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ibm flash copy, hp business copy - Linux / Unix Administration

[email]dfreybur[/email] (Doug Freyburger) wrote in message news:<7960d3ee.0406080727.42c9875aposting.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 ...

  1. #1

    Default Re: ibm flash copy, hp business copy

    [email]dfreybur[/email] (Doug Freyburger) wrote in message news:<7960d3ee.0406080727.42c9875aposting.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?
    yls177 Guest

  2. #2

    Default Re: ibm flash copy, hp business copy

    yls177 wrote:
    > Doug Freyburger wrote:
    > > 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?
    In the HP business copy case you need 200% of the original space.
    That makes it's space consumption predictable.

    In the IBM flash copy case it depends on exactly what you do.
    If you do make a complete extra copy from the checkpoint you need
    very close to 200% of the original space. If you do not make a
    complete extra copy and just depend on the checkpoint your
    consumption depends entirely on your rate of change and it has a
    worst case scenario of 200%. I have no idea what happens if you
    notice that your average amount of change is 5% therefore you use
    a flash pool that's 10% but one day you get 11% change and
    overwhelm the pool.
    Doug Freyburger Guest

  3. #3

    Default Re: ibm flash copy, hp business copy

    [email]dfreybur[/email] (Doug Freyburger) wrote in message news:<7960d3ee.0406100741.6f8be09dposting.google. com>...
    > yls177 wrote:
    > > Doug Freyburger wrote:
    > > > 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?
    >
    > In the HP business copy case you need 200% of the original space.
    > That makes it's space consumption predictable.
    >
    > In the IBM flash copy case it depends on exactly what you do.
    > If you do make a complete extra copy from the checkpoint you need
    > very close to 200% of the original space. If you do not make a
    > complete extra copy and just depend on the checkpoint your
    > consumption depends entirely on your rate of change and it has a
    > worst case scenario of 200%. I have no idea what happens if you
    > notice that your average amount of change is 5% therefore you use
    > a flash pool that's 10% but one day you get 11% change and
    > overwhelm the pool.


    we did a flash copy everyday. its an exact copy of our production

    cheers
    yls177 Guest

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