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Hi All,</div>
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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.</div>
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What happens to the snapshot when a file is compressed in SS? The logic as I see it is </div>
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####### In a non compressed situation ###############</div>
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1) create a file,</div>
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2) create a snapshot.</div>
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3) modify a file in a normal way - the blocks on disk are changed and the old blocks are then written to the snap. </div>
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<p style="margin-top: 0px; margin-bottom: 0px">######In a compressed situation ############</p>
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<div style="margin: 0px; font-family: Calibri, Arial, Helvetica, sans-serif">1) create a file,</div>
<div style="margin: 0px; font-family: Calibri, Arial, Helvetica, sans-serif">2) create a snapshot.</div>
<div style="margin: 0px; font-family: Calibri, Arial, Helvetica, sans-serif">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.</div>
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<div style="margin: 0px; font-family: Calibri, Arial, Helvetica, sans-serif">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.</div>
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Thanks</div>
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Bob</div>
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<strong><span style="font-family:Arial,sans-serif,serif,EmojiFont; color:rgb(0,111,201); font-size:10pt">Bob Cregan</span></strong><span style="font-family:Arial,sans-serif,serif,EmojiFont; color:black; font-size:10pt"><br>
HPC Systems Analyst</span><span style="font-family:Calibri,sans-serif,serif,EmojiFont; color:black"></span></p>
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<span style="font-size:10pt"></span><span style="font-family:Arial,sans-serif,serif,EmojiFont; color:black; font-size:10pt">Information & Communication Technologies</span><span style="font-family:Calibri,sans-serif,serif,EmojiFont; color:black"></span></p>
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<span style="font-size:10pt"></span><span style="font-family:Arial,sans-serif,serif,EmojiFont; color:black"><span style="font-size:10pt">Imperial College London, </span><br>
<span style="font-size:10pt">South Kensington Campus London, SW7 2AZ</span><br>
<span style="font-size:10pt">T: 07712388129</span><br>
<span style="font-size:10pt">E: b.cregan@imperial.ac.uk</span><br>
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<span style="font-size:10pt"></span><span style="font-family:Arial,sans-serif,serif,EmojiFont; color:black"><span style="font-size:10pt">W: </span><a href="http://www.imperial.ac.uk/ict/rcs" target="_blank" rel="noopener noreferrer" id="LPNoLP"><span style="font-size:10pt">www.imperial.ac.uk/</span><span style="font-size:10pt">ict</span><span style="font-size:10pt">/</span><span style="font-size:10pt">rcs</span></a></span><span style="font-family:Calibri,sans-serif,serif,EmojiFont; color:black"></span></p>
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<sub><span style="font-size:10pt; line-height:23px; font-family:Calibri,sans-serif,serif,EmojiFont; color:rgb(31,73,125)"><img class="EmojiInsert" alt="1505984389175_twitter.png" style="" data-outlook-trace="F:1|T:1" src="cid:ba38b5d6-12d6-476a-bcd8-7d647bfab5b3"> </span></sub><span style="font-size:10pt; line-height:23px; font-family:Arial,sans-serif,serif,EmojiFont; color:black">@imperialRCS
@imperialRSE</span><span style="font-family:Calibri,sans-serif,serif,EmojiFont; color:black"></span></p>
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