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DV Backup FAQ
| General Questions |
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Q. What can DV Backup (standard edition) do for me? |
A. DV Backup turns your DV, Digital8 or DVCAM device into a high capacity tape backup drive. Normally such devices cost many hundreds if not thousands of Dollars but with DV Backup you discover that you already own one without knowing it, and that it connects straight into your Mac meaning it can be used right away. DV Backup provides full backup, restore and verify functionality. The DV device is kept under full control of the application, which keeps a table of contents on each tape and can wind directly to get data back from it. You can sit back and watch or do something else, DV Backup does it all for you. DV Backup's backup functionality allows you to choose which files and folders to backup, and to exclude individual files and folders if you wish. It lets you keep regularly-used file and folder configurations in named "sets" so they don't have to be recreated each time. It lets you perform backups incrementally, where only those files and folders which have changed since the previous incremental backup are backed up. All this is supported via an intuitive drag-and-drop interface. It also supports the authorisation of supervisor privileges for access to privileged files without the need to login as root, so you can perform a whole system backup quickly and easily. Once your backup files have been chosen you can select to have your backup compressed, auto-verified (where the tape is rewound and the backup verified automatically once it has finished), recorded in SP or LP, and you can choose the level of protection against tape errors (which allows your data to be recovered even if corrupted by a tape error), before clicking 'Backup' and leaving DV Backup to do the rest for you. When you want to restore your data you can see the files and folders in the backup and choose which ones you want to be recovered. For backups which are not compressed you can enable the "direct access" feature, which winds the tape directly to the files to be restored. This makes access to your files very fast if you want to restore a small number of files contained in a large backup, it is not necessary for the backup to be played from start to end. If you want to have even faster access to your backups you can store them in a hard drive area. You can transfer backups in both directions between this area and tape, so you can place backups in longer-term archive on tape or transfer an older tape archive that will need regularly access onto your hard drive, just by dragging and dropping them between the two areas. The use of the tape space is monitored by DV Backup fully automatically and it will detect if a backup will not fit. If this happens it will allow you to span a large backup over an unlimited number of tapes, requesting you to insert a new tape each time it needs one during the backup. When restoring it will ask for each tape in turn, making sure that the correct one has been inserted before proceeding. Tape capacities are high, up to 17.7GB per hour of tape (LP mode, normal format using the DV audio and video tracks, no error protection), this is almost 4 times as much as a 4.7GB DVD, and more than twice as much as a 8.5GB dual layer DVD. DV Backup contains many other features, but in summary it provides a low cost, high capacity, high reliability backup system to all Mac users with a compatible device. Why not download it and try it for free? |
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Q. What are the requirements for DV Backup to function? |
A. The following must all be satisfied. You will need: 1. A compatible DV, Digital8 or DVCAM camcorder or deck, which supports both DV-in and DV-out (some European models may only support DV-out). |
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Q. What is the tape capacity and transfer speed? |
A. This depends on the level of error protection chosen for each backup. The highest capacity comes with the lowest level of error protection (which provides no protection against any tape errors), while the lowest capacity comes with the highest level of error protection (which fully duplicates all the data on the tape). Also you can record using LP mode and gain 50% more capacity over SP mode. For a 60 minute tape the following table helps to illustrate the capacities available. The first set of figures are based on 1GB being (1024 x 1024 x 1024) bytes (as used for measuring RAM and file sizes), and the figures in parentheses "()" are based on 1GB being (1000 x 1000 x 1000) bytes (as used by manufacturers when specifying hard drive and DVD capacities). Therefore use the latter figures to see how tape capacity compares with hard drive and DVD capacities. 1. LP mode highest
capacity:16.4GB (17.7GB).
Achieved using no error protection.
2. LP mode lowest capacity: 8.2GB (8.8GB). Achieved using full duplication ("1:1"). 3. SP mode highest capacity: 11GB (11.8GB). Achieved using no error protection. 4. SP mode lowest capacity: 5.5GB (5.9GB). Achieved using full duplication ("1:1"). Intermediate levels of error protection allow correspondingly higher tape capacities compared to the highest level of error protection, and capacity is never higher than that permitted when using no error protection. However you can usually significantly increase the amount of data stored on a tape if you choose to compress it when backing it up (compression rates vary depending on the nature of the data). The largest known per-tape capacity known is offered by certain DVCAM decks by recording on 184 minute tapes using DV SP format. This gives a recording time of 276 minutes (4 hours 36 minutes) equating to a maximum storage capacity of 50.5GB (54GB). This is fully supported by DV Backup. A small number of camcorders require the use of "strict" format instead of the default "normal" format. The "strict" format reduces tape capacity by about 15%. All figures are based on the DV audio and video tracks being used to store data. Example data transfer rates are as follows: Normal mode, no
protection: 187MB per minute, 11GB
per hour
Normal mode, full duplication: 94MB per minute, 5.5GB per hour Strict mode, no protection: 159MB per minute, 9.3GB per hour Strict mode, full duplication: 80MB per minute, 4.7GB per hour |
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Q. What features are provided by the lite and standard editions? |
A. The following table illustrates the features provided by each edition:
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Q. If I purchase an access code now, will I need to buy another one to use future upgrades? |
A. No, not for any version 1.x release. An access code will let you use all version 1.x releases without any extra purchase. |
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Q. What is "Direct Access"? |
A. This feature can greatly reduce the amount of time it takes to restore a selection of files from a large backup. Without it the backup must be played from start to end to restore even just one file or folder, but Direct Access enables the accurate winding of the tape to the correct position to extract the selected files/folders, before winding directly to the next selection etc.. This feature is only available for uncompressed backups. |
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Q. Is there a maximum size that DV Backup can backup? |
A. No. You can backup over an unlimited number of multiple tapes if a backup won't fit on a single one (this is not available if using the "lite" edition). |
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Q. Does DV Backup backup HFS+ resource fork information as well as the data fork? |
A. Yes. DV Backup uses hfstar to perform the archive creation and extraction function, which means that both the resource and data fork information will be backed up and restored intact. |
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Q. Does DV Backup work on Tiger, i.e. MacOS X 10.4? |
A. Yes. It works on Tiger, Panther and Jaguar. However early releases of OS 10.4 (up to 10.4.1) contain problems which can cause DV Backup to fail to operate on certain installations. |
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Q. If I send someone a tape created by DV Backup, will they be able to read it with their camera? |
A. If they are of the same TV standard then yes, but if you create a tape on (for example) a NTSC camera and try to use it on a PAL camera, it won't work. It is also possible that some cameras will have difficulty reading a tape created by another camera, whether the tape contains data created by DV Backup or ordinary video. It is important that the version of DV Backup being used to read the tape is the same or newer than the version used to create it. An older version of DV Backup cannot read a tape created by a newer version. |
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Q. Is it possible to backup and restore a bootable volume such that the restored volume is bootable? |
A. Yes, with both MacOS 9 and MacOS X bootable volumes. It will be necessary to run DV Backup as root to do this to enable access to restricted system files. |
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Q. Will there be an OS 9 version of DV Backup? |
A. No, DV Backup is too reliant on OS X's core and Unix facilities to make porting it to OS 9 practical. |
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Q. Will there be a Windows version of DV Backup? |
A. There may be in future once the OS X version is as stable as possible and has a full feature set, however for now the focus is on maturing the OS X version. |
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Q. Will there be a German, Japanese or other international version of DV Backup? |
A. Not in the short term. The current focus is on improving the feature set of the application. |
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Q. Can you selectively restore individual files and folders with DV Backup? |
A. Yes, and using the Direct Access feature the tape can be wound directly to each one to avoid waiting for it to play through the entire backup. Direct Access is only available for non-compressed backups. |
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Q. Will it be possible for a Mac to boot from a camera containing a backup of a bootable volume? |
A. It is highly unlikely that this will ever become possible, it would require changes to the Mac boot ROM to provide support for this, which would require Apple to make the necessary changes. |
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| Common Questions and Problems |
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| Q.
I am thinking about buying a DV device, but I cannot try it in
evaluation mode to see if it will work with DV Backup without buying it
first. Is there a list of compatible and incompatible devices so I can
get a better idea whether it will work in advance of committing to
buying expensive hardware? |
A.
There is a user-maintained database here,
as part of the Yahoo group for DV Backup users. You will need to join
the group to view it, but this is quick, easy and free, and without any
commitment. |
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Q. When I backup my home folder it never verifies successfully. |
A. If you try to backup a user's home folder while actually logged in as that user, the background OS X operations will continue during the backup and they update and change certain files. This means the files have changed when they are used to verify the backup, hence the verify fails. The most certain way to verify a user's home folder backup is to perform the whole operation running DV Backup logged in as root. |
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Q. I have a Canon camera and it fails to read back data recorded to it by DV Backup. |
A. Some Canon cameras have a special mode where they can turn the analogue audio and video input on the camera into DV format and send it to the computer. This must be disabled to use this camera with DV Backup, turn off the "AV -> DV" or "analogue - DV" setting in the menu. |
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Q. DV Backup doesn't report the remaining tape space correctly, and the tape keeps running out when DV Backup indicates there is plenty of remaining space. |
A. This is most likely to be because the tape length (which is set when formatting or erasing a tape) has been specified as the number of minutes at LP recording speed. It is important to enter the tape length as the number of minutes at SP recording speed, i.e. the number shown on the tape's packaging, otherwise the end of the tape will be reached prematurely. It is also possible that there are backups on the tape which have been recorded at SP speed, with DV Backup being told they were LP at the time the backup was created - if so, contact the address at the foot of this page for support. |
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Q. I have a DVCAM deck - the backup keeps failing around 40 minutes into the tape. |
A. This is likely to be because you are recording on a 60 minute DV tape in DVCAM mode. DVCAM records 33% faster than DV, so a 60 minute DV tape only holds 40 minutes of DVCAM video. Switch your deck to record in DV mode, or erase the tape and set its length to 40 minutes instead of 60. |
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Q. The camera test fails with my camera, does this mean I cannot use DV Backup? |
A. Probably. The camera test is very strict so it may be worth trying to perform some backups, restores and verifies, and to save the TOC, eject the tape and then reload it to check the TOC is stored correctly, to see if the camera works reliably in spite of failing the test. If only the eject test fails, the camera will still be likely to work successfully with DV Backup but it is still always worthwhile performing actual backups and restores/verifys to most certain that your camera will work with DV Backup. A few cameras, notably some JVC ones, will not accept the DV video stream that DV Backup currently generates. Try formatting the tape in 'strict' mode - this has been used successfully with a JVC camera which previously would not accept DV Backup's synrthesised video, but the stricter stream imposes a penalty of a 15% reduction in tape capacity so should not be used unnecessarily. |
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Q. When I format a tape with "strict" mode and watch the camera screen, the screen is always blank. Others report the screen changes colour all the time, why doesn't this happen for me? |
A. Strict mode generates the DV video stream in a different way to suit certain cameras which don't accept the normal format. With strict format the screen is always blank as a consequence, it is only normal mode which allows you to see the effect of the computer data on the camera screen. Otherwise there is no change to the operation of DV Backup, except that strict format reduces the tape capacity by about 15% due to the extra overhead it imposes. So if you can, it is always best to use normal format. |
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Q. I set my backups to be recorded in LP mode in DV Backup but the camera records them in SP (or vice versa). |
A. Most cameras do not support remote control of the recording speed from the computer so it is necessary to set the speed manually on the camera itself. So that DV Backup can track how much of the tape is used by backups it is necessary to tell it the recording speed, which you can do when you are about to create a backup. These buttons are unfortunately not for remote control of the camera's recording speed. |
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| Further Questions |
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Q. My question is not in this FAQ, can you help? |
A. Please feel free to send a mail to the address at the foot of this page. The additional FAQ and user manual contained in the free download of DV Backup may also be of help. |
For all queries please contact
DV Backup is Copyright (C) Tim Hewett 2001,
2002, 2003, 2004, 2005, 2006, 2007, 2008