What to do when tape is full?
Another thing I don't quite understand, is what's the best thing to do when I get *** A TAPE ERROR OCCURRED: [[writing file: No space left on device]]. Some dumps may have been left in the holding disk. Run amflush to flush them to tape. The next tape Amanda expects to use is: a new tape. Well, obviously, the simple answer is run amflush, which is what I did the last time I got this. The problem with this was that the flush required a tape of its own, which was not what I wanted; what I really had in mind was to write the dumps along with next day's backups. So what should I have done? Perhaps Amanda would have handled this automatically if I had left the holding disk alone? (I'm sorry, but it's quite hard to test this now, for obvious reasons, and I can find very little information on tape errors in the documentation.) - Toralf
Re: What to do when tape is full?
On Mon, Apr 22, 2002 at 11:39:55AM +0200, Toralf Lund wrote: On 19/04 2002 16:18 Dave Sherohman wrote: You can do this manually by not changing tapes (or leaving the tape drive empty) tonight, which will cause all of tonight's dumps to stay on the holding disk (provided it's big enough), then put the new tape in and run amflush tomorrow morning to collect all of the untaped dumps. Yes, of course. Does this also mean that it's a good idea to use the amount equivalent to one tape of the holding disk space? IMO, holding disk space is a matter of 'the more, the merrier'. You definitely want enough to handle at least one runs' worth of level 1 dumps, in case someone forgets to switch tapes or the taping never starts for some other reason. I like to go with at least twice that (disk is cheap, these days...) so that I can consolidate partial dumps if something goes wrong mid-run. I was thinking that allowing more than one tape's worth of data to be stored on disk would be bad as there might still be something left after flushing an overflowed dump + run without tape, which would leave me in exactly the same state as before I started. Nope. Last night's untaped dumps will sit on the holding disk forever unless you either delete them or run amflush Too bad. Yeah, it would be nice if you could set amanda up to automatically do an amflush onto the same tape after completing a normal run if the tape isn't full yet. Exactly. Or to do amflush first when starting the next run, then do new dumps to fill up the tape. I'm assuming there is no way to continue writing to the tape were something was amflushed, either, but please let me know if I'm wrong. You are correct. Amanda will not append to tapes under any circumstances. It always starts writing from the beginning of the tape. Wouldn't append support be easy to implement? Seems to me that most of the code must be there already (since Amanda writes several dumps to one tape in its normal mode of operation.) - Toralf
Re: What to do when tape is full?
On 23/04 2002 17:38 Frank Smith wrote: --On Tuesday, April 23, 2002 15:26:33 +0200 Toralf Lund [EMAIL PROTECTED] wrote: On 23/04 2002 14:52 Joshua Baker-LePain wrote: Yes, maybe a good decision. (Although the purchase of new tapes and the management of all of them do add up to a non-negligible cost.) While the cost of sufficient tapes is certainly 'non-negligible', and can actually be much greater than the cost of the library you put them, company management has to weigh the cost of tapes versus the cost of losing data. Sooner or later you will need to restore something. How much is it worth to be able to do that? There is much data that can be (somewhat) easily recreated, and other data that is irreplaceable or would take so long to recreate that you would be out of business before it could be recreated. If you don't have enough tapes to be comfortable in the ability to restore your data (and just because you have one copy doesn't mean you will be able to restore it), then get more tapes. If your management doesn't see the need, write up what you need and why, and be sure to save the response if they disagree, since your head is on the line if critical data can't be restored. Many good points, there. These are exactly the considerations my backup configuration is based on, really. I suspect that a lot of people back up their data because conventional wisdom is that they should do it, whereas the backup strategy really ought to be based on an assessment of the cost of backup and recovery vs the cost of recreating data. - Toralf
Re: What to do when tape is full?
On Mon, Apr 22, 2002 at 11:39:55AM +0200, Toralf Lund wrote: On 19/04 2002 16:18 Dave Sherohman wrote: You can do this manually by not changing tapes (or leaving the tape drive empty) tonight, which will cause all of tonight's dumps to stay on the holding disk (provided it's big enough), then put the new tape in and run amflush tomorrow morning to collect all of the untaped dumps. Yes, of course. Does this also mean that it's a good idea to use the amount equivalent to one tape of the holding disk space? IMO, holding disk space is a matter of 'the more, the merrier'. You definitely want enough to handle at least one runs' worth of level 1 dumps, in case someone forgets to switch tapes or the taping never starts for some other reason. I like to go with at least twice that (disk is cheap, these days...) so that I can consolidate partial dumps if something goes wrong mid-run. I was thinking that allowing more than one tape's worth of data to be stored on disk would be bad as there might still be something left after flushing an overflowed dump + run without tape, which would leave me in exactly the same state as before I started. Nope. Last night's untaped dumps will sit on the holding disk forever unless you either delete them or run amflush Too bad. Yeah, it would be nice if you could set amanda up to automatically do an amflush onto the same tape after completing a normal run if the tape isn't full yet. Exactly. Or to do amflush first when starting the next run, then do new dumps to fill up the tape. I'm assuming there is no way to continue writing to the tape were something was amflushed, either, but please let me know if I'm wrong. You are correct. Amanda will not append to tapes under any circumstances. It always starts writing from the beginning of the tape. Wouldn't append support be easy to implement? Seems to me that most of the code must be there already (since Amanda writes several dumps to one tape in its normal mode of operation.) - Toralf
Re: What to do when tape is full?
On Tue, 23 Apr 2002 at 1:30pm, Toralf Lund wrote Wouldn't append support be easy to implement? Seems to me that most of the code must be there already (since Amanda writes several dumps to one tape in its normal mode of operation.) Lack of append support is a design decision, AIUI. The thought is that it's better to not use some of a tape than to overwrite backups because, for some reason, the tape rewound itself when you weren't looking. Safety and redundancy are paramount in backups, not tape usage. YMMV, but that's the design decision made with amanda (which I happen to agree with). If you want to fill tapes to the max, then add the disk usages up by hand and 'amadmin force' enough filesystems each night to fill the tape. -- Joshua Baker-LePain Department of Biomedical Engineering Duke University
Re: What to do when tape is full?
On 23/04 2002 14:52 Joshua Baker-LePain wrote: On Tue, 23 Apr 2002 at 1:30pm, Toralf Lund wrote Wouldn't append support be easy to implement? Seems to me that most of the code must be there already (since Amanda writes several dumps to one tape in its normal mode of operation.) Lack of append support is a design decision, AIUI. The thought is that it's better to not use some of a tape than to overwrite backups because, for some reason, the tape rewound itself when you weren't looking. Safety and redundancy are paramount in backups, not tape usage. YMMV, but that's the design decision made with amanda (which I happen to agree with). Yes, maybe a good decision. (Although the purchase of new tapes and the management of all of them do add up to a non-negligible cost.) I'd really prefer an auto flush mode to append support (I can't see any need for both). That should be easy to write as well, and I can't see any problems associated with it, in fact, I think it would increase the safety quite a bit. If you want to fill tapes to the max, then add the disk usages up by hand and 'amadmin force' enough filesystems each night to fill the tape. I've also thought about reducing runspercycle a bit, and risk not getting everything included - but of course run additional amdumps when necessary, or even have extra ones started automatically, but I'm not quite sure how it would work out in practise. - Toralf
Re: What to do when tape is full?
At 08:26 AM 4/23/2002, Toralf Lund wrote: [...] I'd really prefer an auto flush mode to append support (I can't see any need for both). That should be easy to write as well, and I can't see any problems associated with it, in fact, I think it would increase the safety quite a bit. From amanda(8): autoflush bool Default: off. Whether an amdump run will flush the dump already on holding disk to tape. [...] - Toralf -- Darin Dugan [EMAIL PROTECTED]
Re: What to do when tape is full?
On Tue, 23 Apr 2002 at 9:09am, Darin Dugan wrote At 08:26 AM 4/23/2002, Toralf Lund wrote: [...] I'd really prefer an auto flush mode to append support (I can't see any need for both). That should be easy to write as well, and I can't see any problems associated with it, in fact, I think it would increase the safety quite a bit. From amanda(8): autoflush bool Default: off. Whether an amdump run will flush the dump already on holding disk to tape. Cool -- thanks for pointing that out. Note, however, that it doesn't appear in the 2.4.2p2 docs -- only in 2.4.3b (which is still in beta mode). -- Joshua Baker-LePain Department of Biomedical Engineering Duke University
Re: What to do when tape is full?
--On Tuesday, April 23, 2002 08:52:51 -0400 Joshua Baker-LePain [EMAIL PROTECTED] wrote: On Tue, 23 Apr 2002 at 1:30pm, Toralf Lund wrote Wouldn't append support be easy to implement? Seems to me that most of the code must be there already (since Amanda writes several dumps to one tape in its normal mode of operation.) Lack of append support is a design decision, AIUI. The thought is that it's better to not use some of a tape than to overwrite backups because, for some reason, the tape rewound itself when you weren't looking. Safety and redundancy are paramount in backups, not tape usage. YMMV, but that's the design decision made with amanda (which I happen to agree with). If you want to fill tapes to the max, then add the disk usages up by hand and 'amadmin force' enough filesystems each night to fill the tape. Or leave the tape out of the drive and let it go to to the holding disk, then amflush whenever you have a full tapes worth. As someone who has learned a lot the hard way, I concur with the 'no append' design decision. There is no way to redo a previous backup, and the one time you accidently overwrite a tape will be the time you most need a file that only existed on that tape. Power glitches, I/O errors, SCSI resets, other users, and various other things can easily cause a drive to rewind with your noticing, and they would all be fatal to your data. Frank -- Frank Smith[EMAIL PROTECTED] Systems Administrator Voice: 512-374-4673 Hoover's Online Fax: 512-374-4501
Re: What to do when tape is full?
On Tue, Apr 23, 2002 at 09:54:45AM -0500, Frank Smith wrote: Or leave the tape out of the drive and let it go to to the holding disk, then amflush whenever you have a full tapes worth. Will that work ? When I use amflush I get given a list of days on which amdump ran without a tpe for whatever reason. Then I must choose one of those days and that set of backups is flushed to the tape. To get two or more days onto one tape Amanda would have to support append :-) Regards, Niall O Broin
Re: What to do when tape is full?
On Tue, 23 Apr 2002 at 5:44pm, Niall O Broin wrote On Tue, Apr 23, 2002 at 09:54:45AM -0500, Frank Smith wrote: Or leave the tape out of the drive and let it go to to the holding disk, then amflush whenever you have a full tapes worth. Will that work ? When I use amflush I get given a list of days on which amdump ran without a tpe for whatever reason. Then I must choose one of those days and that set of backups is flushed to the tape. To get two or more days onto one tape Amanda would have to support append :-) I believe the default is ALL. -- Joshua Baker-LePain Department of Biomedical Engineering Duke University
Re: What to do when tape is full?
On Mon, Apr 22, 2002 at 11:39:55AM +0200, Toralf Lund wrote: On 19/04 2002 16:18 Dave Sherohman wrote: You can do this manually by not changing tapes (or leaving the tape drive empty) tonight, which will cause all of tonight's dumps to stay on the holding disk (provided it's big enough), then put the new tape in and run amflush tomorrow morning to collect all of the untaped dumps. Yes, of course. Does this also mean that it's a good idea to use the amount equivalent to one tape of the holding disk space? IMO, holding disk space is a matter of 'the more, the merrier'. You definitely want enough to handle at least one runs' worth of level 1 dumps, in case someone forgets to switch tapes or the taping never starts for some other reason. I like to go with at least twice that (disk is cheap, these days...) so that I can consolidate partial dumps if something goes wrong mid-run. Nope. Last night's untaped dumps will sit on the holding disk forever unless you either delete them or run amflush Too bad. Yeah, it would be nice if you could set amanda up to automatically do an amflush onto the same tape after completing a normal run if the tape isn't full yet. I'm assuming there is no way to continue writing to the tape were something was amflushed, either, but please let me know if I'm wrong. You are correct. Amanda will not append to tapes under any circumstances. It always starts writing from the beginning of the tape.
Re: What to do when tape is full?
On Fri, Apr 19, 2002 at 09:25:02AM +0200, Toralf Lund wrote: Well, obviously, the simple answer is run amflush, which is what I did the last time I got this. The problem with this was that the flush required a tape of its own, which was not what I wanted; what I really had in mind was to write the dumps along with next day's backups. You can do this manually by not changing tapes (or leaving the tape drive empty) tonight, which will cause all of tonight's dumps to stay on the holding disk (provided it's big enough), then put the new tape in and run amflush tomorrow morning to collect all of the untaped dumps. (As I've mentioned before, I've got a flaky tape drive, so I have a holding disk that's big enough for two full nights' dumps and frequently find myself consolidating them in this manner.) Perhaps Amanda would have handled this automatically if I had left the holding disk alone? Nope. Last night's untaped dumps will sit on the holding disk forever unless you either delete them or run amflush.
