Binyamin Dissen wrote:
On Tue, 24 Oct 2006 11:04:08 -0500 Hal Merritt <[EMAIL PROTECTED]> wrote:
:>We just flashed a number of volumes. The flash function reports complete
:>in a second or two, but the physical copy will take a while. There were
:>110 mod 3 volumes, and 40 were mod 27's. About 1.2 tb.
:>Is there any way to tell when the physical copy completes and the target
:>volumes are usable? This is a DS8100 (2107-821).
I thought that flash serialized an image of the drive and that one could
continue using the volume since flash will put updates somewhere else -
without rewriting the serialized tracks - until the physical copy was done.
An attempt to update a track that hasn't yet been copied will result in
the immediate logical copying of that original track to the flashcopy
target, followed by the requested update to the source volume (I would
suspect write completion is reported back once all required data is
preserved in some non-volatile format in the DASD subsystem, not
necessarily when all physical writes have completed). Updates to the
source volume are not deferred until completion of the flashcopy
operation, but only until the affected tracks have been preserved, with
priority given to preserving tracks pending update. In fact, if you do
a "NOCOPY" flashcopy, the only tracks that must be copied to the target
are those updated on the source volume.
Once the FC Establish has successfully completed, the flashcopy has been
successfully initiated (a matter of milliseconds or seconds at most) and
I/O to both source and target volumes is allowed to proceed. After that
point, any attempt to read from the source volume will get a track image
from that volume (or a track image in cache that is pending write to
that volume). Any attempt to read from the target volume will get an
already-copied track from the target volume and un-copied tracks from
the source volume. A partial write of a target volume track that hasn't
yet been copied from the source also requires first reading and merging
data from the original source track.
There are cases where it is useful to know that the flashcopy has
physically completed, but availability of the target volume for I/O is
not one of them. I/O to the target volume may be done as if the full
copy had completed immediately after the flashcopy has been initiated.
--
Binyamin Dissen <[EMAIL PROTECTED]>
http://www.dissensoftware.com
Director, Dissen Software, Bar & Grill - Israel
...
--
Joel C. Ewing, Fort Smith, AR [EMAIL PROTECTED]
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