restore from archive problem

[addesign]

I am using a Macintosh G4 which is connected by scsi cable to a LaCie DDS3 tape drive & using Retrospect 4.3 desktop backup software. All has been working very well for over 1 year, backups, restores, archives & verification transfer rates of an average of 40-50 meg/minute. For the past few months I have been having problems restoring from archives only, restoring from a back-up works as well as ever, but restoring from an archive averages about 2-3 meg/minute. Also archiving files works well, but verifying takes forever. I don't understand what's going on, I've cleaned the heads repeatedly with no improvement. I have made no changes in my system nor my cabling. I don't know if anybody else has ever encountered this sort of problem before, but I would appreciate any help.

 

Thank you in advance.

 

AdDesign

[AmyJ]

If your current tapes are working fine, yet your older, archived tapes are not generating the same performance, it would appear that your older tapes are slowly wearing out. Tapes have a limited life span. Repeated usage degrades the quality and will eventually render the tape useless. See below for articles on tape handling, storage and life expectancy.

 

 

 

From the Knowledgebase:

 

www.dantz.com/index.php3?SCREEN=knowledgebase_article&id=529

 

 

 

A secure backup strategy which includes maintaining not only good backups, but rotating off-site backup is important. This is something we try to stress with almost all of our Tech Support phone calls that involve backup strategies.

 

 

 

Another aspect to a secure backup strategy is the proper maintenance of backup media. While it is important to get your backup media off-site, the transportation and storage of that media can have a drastic effect on it's integrity. Keeping media in the trunk or glove-box of a car for instance can seriously compromise that media.

 

 

 

Improper storage of backup media can be a killer for DAT, Travan, DLT and other types of tape.

 

 

 

Often users have done several things wrong:

 

 

 

1) Made only one copy of the original data before deleting it from the hard disk

 

2) Backed up the data with verification turned off

 

3) Stored the backup media in an environment that contributed to media failure

 

 

 

Media life totally depends upon how the media is stored and taken care of. To help maintain maximum media integrity, we would like to offer the following tips:

 

 

 

1) Avoid temperature extremes. Storing backup media (of any type) in a car can expose the media to extreme cold or heat depending on the time of day. The temperature in a car over a year can easily range from 20° to 127 °F.

 

 

 

2) Magnetic media's worst enemy is moisture/humidity. If tapes get wet or moist, or are stored in a very humid environment, they deteriorate. Consistent humidity is important. 50% relative humidity is ideal.

 

 

 

3) Particulate Contamination also compromises your backup media. Media stored in a dusty or dirty environment (like a factory or warehouse) can damage tapes (or increase the chance of scratches in CD-R media).

 

 

 

Storing backup media in a fire-proof safe in a climate controlled building is always better than keeping something in your desk drawer at home (especially if that desk gets hit by sunlight each day, etc.)

 

 

 

4) We have heard stories of problems with EMF causing problems for tapes. One tape vendor told a story about a user who stored his DAT tapes in his briefcase along with his Cell phone. Exposure to the Cell phone (in standby and ringing from time to time) was suspected as a cause for data integrity problems with his backup tapes. This could be an urban legend but it is better to be safe then sorry later.

 

 

 

Dantz is committed to making sure that not only can users back up data, but they are able to restore that data years later.

 

 

 

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This is information that has been obtained from HP.

 

 

 

Life-Expectancy of Tapes

 

 

 

All DDS-certified media is electronically checked to withstand at least 2000 passes. Under optimum environmental conditions (50% relative humidity, 22°C), this is equivalent to about 200-300 backup operations. This takes into account that an area of tape may have several passes during a backup, either because streaming cannot be maintained, or because the backup software package repeatedly accesses certain areas of tape.

 

 

 

Under certain extreme conditions, the recommended maximum number of backup operations is less. These conditions are as follows:

 

 

 

• Environmental Conditions: Sustained use at the low end of the humidity specification will reduce the tape life.

 

 

 

•Computer Performance: The lower the performance of the computer, the more likely that streaming cannot be maintained and that an increase in the number of passes over given areas of tape will occur.

 

 

 

•Backup Software Package: The backup package may access certain areas of the tape frequently, or there may be a high system overhead which may cause streaming to stop. Both of these factors increase the number of tape passes in a given area.

 

 

 

Because these parameters vary from system to system, it is difficult to give a definitive statement of the number of backup operations achievable using a particular tape.

 

 

 

As a guideline we recommend that you limit the use of a tape to around 100 backup operations in worst case conditions of the following:

 

 

 

•Environment: Sustained low humidity

 

•Computer Performance: Streaming failures

 

•Backup Software Package: Accessing certain tape areas frequently, or causing streaming failures.

 

 

 

An added note about Humidity: To avoid condensation problems, allow a tape to stabilize after it has been moved from one temperature and humidity to another for at least two hours before you use it.

[addesign]

These are new tapes that I am using. For example, if I take 2 brand new tapes, do a back-up task on one and an archive task on the other of the exact same files, retrieving from the back-up catalog will be done at 40-50 meg/minute, but retreival from the archive catalog will be at 2-3 meg/minute.

[AmyJ]

Thanks for the update. Backup Set catalogs and Archive catalogs are the same thing within Retrospect. A backup set is a container for the data - the backup vs. archive only decides what data goes into the container (backup set), but is not any different functionally.

 

 

 

What are the differences between and archive and a backup?

 

 

 

Archive has the ability to delete the original files ("move files" option) from the hard disk following the copy and compare phase of the archive processes.

 

 

 

Archive has matching disabled by default. This means that the archive scripts copy all files from the source, even if those files were previously written to the backup media.

 

 

 

Both a backup and an archive use snapshots and store the data the same way within the set. In fact, you can execute backups and archives within the same backup set. The archive may have more files, as matching is turned off, but that should not translate into such a discrepancy in speeds when restoring the same files. That you are seeing such a difference, would seem to indicate a problem with the tape. Although it is brand new, that does not rule out the possibility that you have a bad piece of media. Try reversing the test - run the backup on tape you designated for archive, and the archive on the tape you originally designated for backup.