Hi All,
Can someone answer the following question on compression in a
snapshot context? We have tried various experiments and they are inconclusive -
too tedious to go into the detail.
What happens to the snapshot when a file is compressed in SS? The logic as I
see it is
####### In a non compressed situation ###############
1) create a file,
2) create a snapshot.
3) modify a file in a normal way - the blocks on disk are changed and the old
blocks are then written to the snap.
######In a compressed situation ############
1) create a file,
2) create a snapshot.
3) Compress the file. Now IBM says the blocks are rewritten when the file is
compressed. So do the old uncompressed blocks go into the snap? If so we now
have 2 copies of the file and unless the compression > 50% we have used more
space until the snap is deleted.
You get the space back in the end, but if you are in a tight situation then
potentially compression might not work for you in the short term.
Thanks
Bob
Bob Cregan
HPC Systems Analyst
Information & Communication Technologies
Imperial College London,
South Kensington Campus London, SW7 2AZ
T: 07712388129
E: [email protected]
W: www.imperial.ac.uk/ict/rcs<http://www.imperial.ac.uk/ict/rcs>
[1505984389175_twitter.png] @imperialRCS @imperialRSE
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