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VXA 320 not getting good compression with Retrospect 6.1 Workgroup

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We just installed our new VXA 320 autoloader and it is great! However, my dreams of getting 320gigs per tape have apparently been dashed. The unit seems to average about 160-180gig per tape, which is way better than my old AIT 35gig tapes but I had hoped for better compression.


Is anyone out there having better/similar/worse results using the VXA 320 with the X23 Cartridges?


Thanks, Chad smile.gif

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Just for comparison, we are getting about 110 to 119 GB per X23 tape on our Exabyte VXA-2 1x10 1u SCSI on our single-processor 2.0 GHz Xserve G5 with an ATTO UL4D. As you may be aware, it's a function of compressability of the data and also the speed at which the tape drive is fed data by the system (which would be affected by the networked client's speed, the network infrastructure speed, the server's speed, the SCSI interface card's speed, server load by other concurrent processes, etc.). I note that Exabyte's vxatool has a hardware setting that can be selected for "optimize for speed" or "optimize for capacity" on the drive, but I've never fooled with it. Don't know which way Retrospect sets this, but I can imagine that the drive lowers the density if it is frequently getting starved for data so that it doesn't have to back up.


My suspicion is that there's no way to get close to the marketing hype maximum capacity until (if) we see D2D2T for Retrospect Mac. I discussed this with an Exabyte tech a while back and he said that people typically see about 1.8 times or so as much data storage on the 320 as is seen on the VXA-2. At current X23 tape prices, the drive upgrade to the 320 pays for itself in less than two autoloader fills, so I'm interested to see a report from another Retrospect user with a 320 to assess whether to upgrade.



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Thanks for the help, very informative. I spoke with my Exabyte rep and he suggested that I try compressing some of the files that I am backing up with stuffit. He said that this should give me a rough idea of the overall compress-ability of the data that I am dealing with which is raw audio files, ie. WAV files.


Stuffit yielded a file that was about 20% smaller than the original, so no where near a 2 to 1 ratio that I was hoping to see. Never the less, the VXA 320 is awesome and I shouldn't complain, it is working great and it will pay for itself over the AIT system we formerly used in about 2 months.


Thanks, Chad

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Be sure you're using firmware 13204 (latest firmware). My tape capacities went way up with that version, apparently they put some code in to deal with the LSI SCSI chips that Apple/Atto use. I also really like Exabyte due to the tech support. They seem knowlegable and willing to take the time to help.


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