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Music servers and other computer based digital audio technologies.

RE: "2. Sooner or later, you will lose data, no matter how many backups you make."

Errors don't permeate the lot if you backup media files correctly.

The way I do it is to run a file sync program. It detects a new addition to the library and copies it automatically (each night) to the backup. However, if a file of the same name already exists on the backup system then it doesn't overwrite the backup. Instead, when I check that the backup ran OK, I get an error report. If the library copy gets corrupted after it's backed up (the one and only time) then the good version will be on the backup. Similarly, if I mistakenly delete the library copy, I will get an error report, but the backup will not be disturbed.

The backup software verifies each file in the library every night and compares it with the backup. Normally, the verification includes checking the file name, file size and file modification time. This is sufficient to catch corruption caused by application software errors or "cockpit" error. It won't catch errors due to hardware glitches. However, the spec on undetected errors is something like 1 bit corrupted in 10*18 bits transferred unless the machine is broken and crashing all the time. Data corruption errors on disks are almost certainly detected and usually corrected automatically with the data rewritten in a new sector.

It is also possible to use my file sync software to do an actual bit for bit compare of all of the files, but this is slow. My onsite backups are on a separate computer system on my LAN and transfers are over a 1 GB Ethernet, so comparisons take about 10 seconds per GB, so doing a full comparison takes a while. My backups are on a NAS and when I replaced all of the disks on a NAS I did a full compare, it took about 24 hours. No errors were detected.

If you run multiple disks off the same computer you will not gain much in reliability, since there can be hardware failures that destroy both disk drives, e.g. a bad CPU doing random writes to disk, a bad power supply that trashes both disk drives, etc...

Bottom line, if you are a competent IT professional, you can reduce the risk of data loss below other risks, such as fire, flood, theft, etc..





Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar



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