Hello, I'm looking for some feedback from the Amanda team on the future of tape spanning of backup images in Amanda.
It always pleases me when I see Free and Open Source software score a success and it would be nice to see Amanda as one of those successes. You may say "What's he talking about? Amanda is already a success!" and you would be right, but only up to a point. So before you discount these comments as those of a newbie who doesn't see the "big picture," please read on a little and consider. My experience with computer system backup goes back to the days when we used punched paper tape and cards to do backups. I've used 800 BPI to 6250 BPI 9-tracks, exabyte's, DAT's, various IBM cartridge's, DLT's of EVERY type, as well as some really exotic backup media like optical tape. Our lab has been involved in Free and Open Source development since long before the term was coined. We had the first ARPANet site in Canada back when TCP/IP was initially being developed. We have developers on staff who made contributions to Stallman's original TOPS-20 EMACS and we have spent lot's of money over the years buying support for things like the GNU development tools knowing full well that in the long run everyone would benefit from the efforts of those programmers who got to work full time on the tools because our support dollars went to pay their salaries. As a result I feel that I have some perspective to bring to this issue. As I said, it would be nice to see Amanda as one of those successes. In order for a software package to be a success, it has to reach a critical mass or it winds up dying. In my experience Free Software that has reached critical mass has a much longer lifetime than any proprietary stuff (I use GNU Emacs and the Gnu Tools for software development and see no end in sight for them). Amanda risks maintaining it's critical mass every time some IT shop considers choosing it as their backup solution and then walks away because Amanda assumes that individual tape media will ALWAYS be bigger than individual filesystems. This assumption has not always been so in the past and just because it has been so for a few years I see no reason why we should expect it to continue to be so in the future. There will always be a race between technologies for the biggest or fastest and there is no telling who is going to be out front next week, let alone next year. It is not reasonable to design a system that you know is likely to break whenever disk capacity pulls ahead in the race. If in that eventuality you are going to have to adopt another backup solution, the reasonable choice is to adopt that other backup solutiuon now. I understand that the Amanda developer's concern is about reliability and it should be. However, our concept of what constitutes a reliable system is subject to change every time we change our perspective. For instance, if we focus on a specific instance of a system and note that it is available to it's users 100% of the time 24 hours/day and 7 days/week and allows those users to perform the job that the system was originally specified to perform, we could define that system as a 100% reliable system. Let us now expand our view to encompass a larger portion of the parent organization. We still see the system we were just focused on is humming away at it's originally intended job. We also see a new system constructed in the room next door at considerable effort and expense. This new system will perform not only the job of the first system, but some expansion to the original requirements of that system. This is an expansion that the organization would have made some time ago, but the original system, just wasn't flexible enough to allow the expansion, so the organization put off spending the resources for an entire new replacement system because of the large one-time cost. In the meantime, the lack of the expanded functionality has cost them business, set back their research program or whatever it is they do. Was the first system 100% reliable? Did it fulfill the organization's requirements all of the time? In my view, it didn't In my experience, a reliable computer system is one that can evolve steadily and smoothly along with the needs of the parent organization without causing major disruptions in how the organization operates. When I look at candidates for a system component, one of the first things I assess is it's long term viability. If the component is an expensive one (and compared to other computer system components reliable tape drives historically are) then that component better have a long useful lifetime and the lifetime of the software I use with that expensive hardware had better match or exceed the lifetime of that hardware. Our lab has paid good money for backup solutions in the past and will continue to do so in the future. We are yet again looking for a backup solution. I'm providing recommendations for software and would love to recommend Amanda but unless I see a commitment to include image splitting in Amanda I can't recommend it and that would be a pity. regards :-) BruceS BTW. One of my favourite backup solutions was VMS backup, particularly in the days of 9-track tapes when tape and drive reliability was a real issue. To counter this, VMS backup wrote lot's of redundenacy info on the tapes and on a number of occasions, when I had managers raising questions about the reliability of various backup solutions, I enjoyed demo'ing VMS backup's reliability by breaking a tape in the middle and cutting a few inches out of the middle of the tape and splicing it back together. Upon restore VMS backup would note "Tape Error - restoring from redundancy block" and continue a flawless restore. :-) ::backup: -- Bruce S. Skinner Defence R&D Canada - Atlantic 9 Grove St. <mailto:[EMAIL PROTECTED]> P.O. Box 1012 <http://www.drdc-rddc.dnd.ca> Dartmouth NS CANADA tel: (902) 426-3100 x205 B2Y 3Z7 fax: (902) 426-9654
