On Sun, 8 Apr 2007, John Drescher wrote: > And then there is reliability. I from my own experiences I can > easily say that DVD media is less reliable than tape but it does > depend on several factors. I would never use RW media for a backup
That really depends on the media. CDRW is far more reliable than CD-R, but suffers from lower reflectivity. > and always make at least 2 copies of your data if you are archiving I'd argue that for tapes too. Apart from anything else it allows one set of archives to be destroyed for any reason while still having copies. > and you should always verify a dvd backup after running it as if a disk > is defective there is a chance that it will write without any errors but > be totally unreadable after. I had that happen two weeks ago at home. Good practice dictates that archived media should periodically be pulled and checked for readability. FWIW: I "retired" a 500 CD 4 drive autochanger about 2 years ago - it had been sitting in a cool cupboard for a couple of years before that, loaded with media and was in an airconditioned room while operational. Part of that retirement was copying all the CDs which had been left in the thing to disk so researchers could assess if they needed the data anymore. Of the 480 CD-R discs in the unit, 2 were unusable to the point of locking the drives up (causing scsi resets) and another 6 had various (recoverable) errors which resulted in some data loss. ALL of them had various levels of CIRC errors reported by the drives themselves ranging from mild to barely recoverable. Those disks ranged between 5 and 7 years old at the time. The unit was taken out of service because of those bad discs. Every time the system encountered one, the entire changer would become unusable until the host computer (solaris) was rebooted. Eventually it was deemed "too much hassle". This happened before I started working here. CD/DVD autochangers may work well for some purposes, but I'm leery of systems with multiple drives on a single bus because of the reset issues just mentioned (applies to tape drives too). Using DVD as backups for home/hobby machines without an autochanger can also be an issue, given that backing up 300Gb of data will require 75 4.7Gb discs (I won't exceed 4Gb per DVD as the closer one gets to the outside edge the higher the chances are of failure) and that starts using considerable amounts of physical storage space. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Bacula-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/bacula-users
