random Posted March 11, 2002 Report Share Posted March 11, 2002 Hello, I posted the following on the HP DAT forum last week. I am hoping that this community might be more helpful: ------------------------------------------- Hello, I am using Retrospect 4.3 on a G3 (O/S 8.5.1) connected to an external SureStore 40. H/W compression is turned on in Retrospect. We DON'T use encryption. The backup sets are showing estimated sizes of 40 GB. Yet when I look at the members within the backup sets, it shows a request for a 2nd tape at the 20 GB mark. I have checked the docs, the compatibility list on both Dantz's site and HP's and it all checks out. I even went to the tape manufacturer's web site (Maxell) and confirmed the proper tape type and size are being used. The docs are mainly text, with one or two people being image heavy. I mention this as I know that images do not compress well. I also can't find much documentation period on the HP site for Macs, so I have no idea if I need to be playing with the DIP switches and the like. Normally I'm the guy people come to with mac questions but this one has me stumped. Any help is welcome. Link to comment Share on other sites More sharing options...
Mayoff Posted March 11, 2002 Report Share Posted March 11, 2002 Is this a DDS-3 or DDS-4 drive? What is the tape length? What type of data do you back up, digital video, audio and system files will usually not compress, resulting in a capacity closer to the "native" capacity. Link to comment Share on other sites More sharing options...
random Posted March 11, 2002 Author Report Share Posted March 11, 2002 Sorry for the lack of details. Tape drive type: DDS 4 (HP surestore 40 external - SCSI connect) Tape type: DDS 4 (150 m) Mac type: Beige All-in-One G3 Files are a mixed bag as indicated in my first post. I am trying to confirm text/non-text ratio. Addendum: I did a test of a 1 MB (approx) ALL TEXT backup with H/W compression on and found that the member size was still over 1 MB, as opposed to the expected 0.5 MB (approx). In fact it was 1.4 MB!!! Should the member size reflect the compressed value or should it reflect the native value? I will do a S/W compression if that is possible given that the drive has built-in H/W compression. Can one overide the hardware compression in favour of a software compression backup? Link to comment Share on other sites More sharing options...
random Posted March 11, 2002 Author Report Share Posted March 11, 2002 Confirmed: H/W compression not working. I repeated the same test I did earlier today, this time with H/W compression turned OFF (again with new backup set and clean tape) and S/W compression turned ON. This time the 1.1 MB folder of text files were compressed to just over 600 KB as reported by looking at the member list. Unless someone can point me to a quick solution, I guess it is up to either Retropsect tech support or HP tech support or both. :-( Link to comment Share on other sites More sharing options...
Mayoff Posted March 11, 2002 Report Share Posted March 11, 2002 When you used software compression, what was the percentage of compression reported in the operations log? If it reports, 0% compression, then the hardware compression will also get around 0% compressions. Fill a tape using software compression, is the capacity higher then without software compression? The total number of MB in the members tab may not reflect just data. The member contains snapshots, catalogs and other Retrospect files that do take up a small amount of tape space. Link to comment Share on other sites More sharing options...
random Posted March 12, 2002 Author Report Share Posted March 12, 2002 From the operations log: S/W compression test: 45% (as expected by the totals I reported in my last two posts) H/W compression test: no value shown. (I take this to mean 0%) It is as if the drive's compression algorithm was never engaged, even though H/W compression was enabled and the drive was recognized by Retrospect 4.3 as a Data Compression (DC) drive. So again, is this a fault in Retrospect or the HP drive? Link to comment Share on other sites More sharing options...
Mayoff Posted March 12, 2002 Report Share Posted March 12, 2002 When hardware compression is in use, no compression values will be displayed in the operations log. Once again. You should create a Backup Set with Hardware and Software compression turned off. Fill up a tape. Note the total number of GB written to the tape. Create a new backup set with hardware compression turned off and software compression turned on. Fill up the tape. Note the total number of GB written to the tape. Compare the capacities. What are they? Link to comment Share on other sites More sharing options...
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