dfigucio Posted February 24, 2003 Report Share Posted February 24, 2003 When running eralier versions of retrospect under OS 9, I woudl easily get 17+ Gb onto a DDS3 Tape. Now I am running Retrospect 5 under MacOS X, and I am lucky to get 12Gb. Hardware compression is not disabled, as under "Configure Devices" the tape info shows hardware compression. I thought this may be an OS X issue, so I went back to OS 9 for a while, but it was just as bad. Same files, same computers - updatated clients obviously... Restores work quite fast but backups are just dang slow. Any ideas? The standard spin of compression can't apply, because there has been no change to what's being backed up - to me it is obviously a performance degardation in Retrospect... d. Link to comment Share on other sites More sharing options...
AmyJ Posted February 24, 2003 Report Share Posted February 24, 2003 There are many variables involved in capacity and compression. Take a look at this FAQ. Tape Capacity and Compression FAQ Restores work quite fast but backups are just dang slow. Backups done while booted into OS X may run slower since OS X’s multi-tasking environment must allow processor time to other processes and applications. As a result, a computer being backed up is far more responsive to the user, and background functions, including file sharing and printing, continue to run at a reasonable speed. Under Mac OS 9 or earlier, a larger portion of the system’s resources are unavailable because they are used for backup. While backups may run more quickly, the computer will likely be sluggish or less responsive during the operation. Link to comment Share on other sites More sharing options...
mcswgn Posted February 25, 2003 Report Share Posted February 25, 2003 Quote: When running eralier versions of retrospect under OS 9, I woudl easily get 17+ Gb onto a DDS3 Tape. Now I am running Retrospect 5 under MacOS X, and I am lucky to get 12Gb. [...] Restores work quite fast but backups are just dang slow. Odds are these are related. On many (all?) tape drives, if data is coming in at a rate slower than it can be written to the tape (so the buffer is empty), the tape will continue to run and the drive will write nulls until it gets more data. (This is because it is very bad for the drive heads to keep going back and forth finding where it last stopped writing the tape.) Clearly, this will reduce the capacity that you see on the tape. So if the backup speed drops below a critical point, the tape capacity will suffer. Link to comment Share on other sites More sharing options...
dfigucio Posted March 2, 2003 Author Report Share Posted March 2, 2003 My main question, however, is why has this degraded when the only apparent change is the version upgrade from 4.x to 5? If I run 4.x under OS 9 I am back to where I was in terms of better tape capacity. If I run 5 under OS 9 backing up the same clients, I lose the tape capacity. No improvement backing up using 5 in OS X. This is not a "Tape Capacity and Compression FAQ" issue - otherwise I would not be getting the capacity in 4.x. There is a definite performance loss running 5. d. Link to comment Share on other sites More sharing options...
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