kelufeng Posted January 8, 2008 Report Share Posted January 8, 2008 Details: vxatool V4.62 -- Copyright © 1996-2006, Exabyte Corp. Tape Drive identified as VXA2 TAPE1 - Vendor : EXABYTE TAPE1 - Product ID: VXA-2a TAPE1 - Firmware : 2122 TAPE1 - Serialnum : 0085237026 TAPE1 - Cleaning : 12 Tape Motion minutes ago Firewire drive using Retrospect 6.1.138 on Dual 2GHz PowerPC G5. I'm unable to get compression to work – either hardware or software. One volume I'm trying to back up is about 85 GB, and it won't quite fit on a X23 80/160 no matter what I do (this example is why I think the estimate of 77.8 GB per tape is pretty accurate – this is consistently what Retrospect reports +/- 0.1 GB). I've used the vxatool to turn hardware compression on and off; while hardware compression was turned off I tried enabling software compression, but got the same results. I don't know much about how this works, but I tried zipping some of the data (mostly Office docs, pdfs, etc) just as a test and it is compressible by software – usually 20-30%, so I can't see why this isn't working. Tandberg support hasn't been very helpful; my last email exchange they asked me to check the block size, which I'm unsure how to do. They said both Retrospect (under configurations) and the vxatool could report the block size, but I don't see the option anywhere and they haven't replied to my email asking for the specific command in the vxatool. Does anyone have any advice? Quote Link to comment Share on other sites More sharing options...
kelufeng Posted January 8, 2008 Author Report Share Posted January 8, 2008 Oh, and I'm running OS X 10.4.11 Server. Quote Link to comment Share on other sites More sharing options...
rhwalker Posted January 8, 2008 Report Share Posted January 8, 2008 What happens when you use vxatool to write stuff to the tape? Can you fill up a tape (compressed) with vxatool? It may be your data. I'm seeing about 115 GB on an X23 tape with VXA-2. Russ Quote Link to comment Share on other sites More sharing options...
kelufeng Posted January 9, 2008 Author Report Share Posted January 9, 2008 The thing is, if Retrospect's reporting is accurate I always get the same amount of storage (77.8GB +/- 0.1 GB) over different data collections, which to me means either all my data is uncompressible, compressible by exactly the same (very small) amount, or compression isn't working. Here's a write test, read is still in progress; I can post the final result in a bit. singapore:/Applications/Exabyte admin$ ./vxatool TAPE1 -t -m 99999 vxatool V4.62 -- Copyright © 1996-2006, Exabyte Corp. Tape Drive identified as VXA2 TAPE1 - SCSI Load Tape...OK TAPE1 - Test size = 99999 MB (command line override) TAPE1 - Rewriting Logical Begin of Tape (LBOT)...OK 0 Writing 99999Mb [WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW] 100 % TAPE1 - Reached end of tape after 68440 MB Let me know if that's not what you meant. This tape has just been used once, assume I should be getting about 80GB, so I'm a bit confused about the 68GB result. Let me know if you have any ideas, thanks for the help. Quote Link to comment Share on other sites More sharing options...
rhwalker Posted January 9, 2008 Report Share Posted January 9, 2008 Quote: Let me know if that's not what you meant. Well, I intended that you would turn on compression and to perfer "Capacity" (over speed) in vxatool before doing that write command. That would show how the device performs when compression is known to be on and the algorithms are set for small inter-block gaps. e.g., ./vxatool TAPE1 -C 1 -P C Quote: This tape has just been used once, assume I should be getting about 80GB, so I'm a bit confused about the 68GB result. We don't know anything about your Firewire setup. (1) are you using the Firewire 800 port (back) or the Firewire 400 port (front) on the Xserve? (2) any other firewire devices on that chain? I wouldn't expect the same performance from the Firewire version of this drive as from the SCSI version (which we have). Also, did you start at BOT? Russ Quote Link to comment Share on other sites More sharing options...
kelufeng Posted January 10, 2008 Author Report Share Posted January 10, 2008 Firewire 800; no other devices on firewire. I erased the tape in vxatool first; admit I don't know if that makes it return to the beginning. Sorry I'm pretty new at this. It's doing a backup now, but I'll try the write test with the capacity optimization this afternoon. I did turn on compression using the ./vxatool TAPE1 C 1 command before the previous write test posted above. Thanks again for the help. Quote Link to comment Share on other sites More sharing options...
rhwalker Posted January 10, 2008 Report Share Posted January 10, 2008 Quote: I erased the tape in vxatool first; admit I don't know if that makes it return to the beginning. I always eject then reinsert from our autoloader before doing vxatool to be sure that it's at BOT. Erasing the tape first raises a different question. Are you sure you did the erasure to put down the VXA-2 header? Probably so, from your results, but the reason I point this out is that Exabyte ships the X23 tapes with VXA-2 headers on them. The VXA-3 (a/k/a/ VXA-320) drives, using these tapes, will operate in VXA-2 mode (half of the VXA-320 density) unless you erase in VXA-320 mode first to prepare the tapes. It's bitten a lot of people. It's for "compatability" reasons so that you can be sure that a tape written on VXA-320 will be readable on VXA-2 unless you really want the extra compression. There's a similar feature with VXA-1 / VXA-2, so just make sure you didn't accidentally put down a VXA-1 header. Note that power cycling of the drive restores all of the settings. I've had that burn us after an extended power fail. Our VXA-2 with autoloader stays powered always from our server's UPS to prevent this, and does not power cycle with the server. Let us know your results. Personally, I chalk up the tape capacities to marketing hype, and I never believe marketing people anyway. I've never done tests on the Firewire VXA-2; only SCSI (we attach to a UL4D in our Xserve), and we seem to be able to keep the drive I/O pumped unless doing network backup from a slow client. Wish we had D2D2T, but that's a different issue. Sigh. Russ Quote Link to comment Share on other sites More sharing options...
dasystem Posted June 9, 2009 Report Share Posted June 9, 2009 Since the VXA drive was marketed as 320gb... I faithfully assumed it would hold close 320gb of compressed data. I have 11 X23 tapes that all have maxed out at 160gb. So i called Tandberg Data. They finally returned my call and assured me that I would never achieve a 320 gb back up as advertised, he actually laughed and agreed that the marketing was false. He claims I am only getting half the capacity (160gb) because I have photoshop files and video files, and to get the full compression (320gb) it would have to be completely text files. Why was this not stated on their websites or literature? Unless your Steven King, this is highly unlikely. My company has sunk over two thousand dollars between the VXA 320 drive, scsi adapter and backup tapes that are only half full when maxed out, how can we be compensated for this false advertising? It is embossed on the machine itself "VXA 320", it should say "VXA 160, unless you have text only files". When you pay for an 8" sub you dont walk out with a 4" sub. Quote Link to comment Share on other sites More sharing options...
rhwalker Posted June 9, 2009 Report Share Posted June 9, 2009 dasystem, what is the purpose of posting this same rant six times? You didn't do your homework. dasystem rant Quote Link to comment Share on other sites More sharing options...
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