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Compression and Encryption in Disk-to-Disk and Disk-to-Tape Questions

Level 3

Running BUE 20.6 and experiencing issues & confusion with compression and encryption in our environment. 

Exactly how does the compression and/or encryption of the main backup job affect the duplicate job?  In our case, we are running the disk-to-disk job with software compression turned on, and no encryption.  The duplicate step of that job then goes disk-to-tape and has no compression but hardware encryption turned on.  We are experiencing issues with the D2T step with those jobs taking longer than expected and in some cases, hours longer. 

1)  Does BUE decompress the data from the D2D step prior to encrypting and writing the data out to tape?

2)  Does the "maximum file size" setting under Storage on our D2D drive have a significant impact on read/writes?  We are currently set to 50GB.




   VIP    Certified

1) No. The data on disk is not decompressed before being duplicated.  Therein lies your problem.  Encrypting compressed data could result in a bigger file than the source.  Turn off your disk compression and then use hardware compression and encryption to tape.

2) It can have an impact.  This is the size of the file that BE allocates to do its back-up.  The smaller the max. size, the more allocation needs to be done by BE hence more time.  However, over-allocating this max.size would result in disk space wastage if the files does not get filled up and also it would be more difficult to allocate big file sizes.

1)  Good to know, wasn't sure if it would decompress or not.  In our situation, I don't really need or want compression of data out to tape as the nightly backup jobs have more than enough room on a tape.  Encryption though is required.  So let me ask this, is it faster to compress the data being written to tape than not?  I would assume BUE would have some type of pre-processing done against the data to compress before it writes out to tape.  Does this hold true and would it make writing to tape faster as it is giving it a steady stream of data?

2) Is there any guidance from Veritas on what this value should be?  Ours is set to 50GB, but I can't remember if that was a default setting or something we chose.  Looking at the files the D2D operation creates, I do some some wasted space but overall most of those BKF files are right at the size limit.

Thanks for the response and information!

   VIP    Certified

1) No.  It would be faster to let the tape drive do hardware compression.  There is no pre-processing done by BE.

2) 50GB is the default max. filesize.  You can adjust it to suit your need.  You also got to watch out for disk fragmentation when setting the filesize.