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Rick Heiges

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Compression in DB Mirroring

When you start to look at SQL Server 2008, there is a sub-theme of using compression to help drive performance and usefulness.  When I hear the word compression, my first thought is "No - I remember Stacker".  How many years ago was that obscure reference?  Too many...  Stacker was a third party product for MS-DOS which basically doubled your disk space.  It worked, but it also seemed to increase chances for corruption on those old disks.  I can't recall the exact name of the product, but there was also a third-party product which compressed RAM to give you more of that too.

SQL Server 2008 will use compression when transmitting the transaction from the principal to the mirror.  Since a majority of DB Servers are not CPU-bound, there are spare cycles to get the compression of this task done quickly.  The goal of using this compression technology is to cut down on network latency.  We have all seen this when we have a large file to transfer over the network.  It is often faster for us to ZIP a file, copy it over the network and unZIP it than it would be to simply copy the file without being zipped.  The same logic applies here. 

Compression is used in other areas of SQL 2008 as well such as backups!  More on that later in a future blog post perhaps.

Published Tuesday, November 20, 2007 7:19 AM by RickHeiges

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AaronBertrand said:

"RAM Doubler" comes to mind.  I'm sure there were others.

November 20, 2007 7:21 AM

cinahcaM madA said:

I don't remember corruption being an issue with those products, but performance certainly was.  Most DB servers, unlike my 486-DX50, have CPU time to spare so I think compression is a great idea these days...

November 20, 2007 8:38 AM

RickHeiges said:

I was bit more than once on a compressed drive.  The other disk tools available at that time that allowed you to look deeper into the disk internals did not work well on compressed drives.  From what I remember, the entire disk was compressed.  It was not until later that we had compressed folders (like in NT series).  

RAM Doubler - yep that was a name...  I did not buy that one, but I used an off-brand one called "ant hill" or something like that with the cover of the package showing little memory chips marching up a hill.  Before SIMM/DIMM chips, adding memory was a HUGE pain aligning the "legs" of the memory chips to the socket holes.  What FUN!!!

November 20, 2007 11:01 AM

AllenMWhite said:

Rick, you look too young to remember all that stuff.  You've either discovered the fountain of youth or you started playing with this stuff when you were six!

Now, get off my lawn, kid.  ;-)

November 20, 2007 2:54 PM

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