On Mon, Nov 18, 2019 at 02:48:40PM +0700, Olivier wrote: > Charles Curley <charlescur...@charlescurley.com> writes: > > > So in theory you could allocate more vtape space that there is room on > > the partition. Just make sure you never use more vtape space than you > > actually have. > > In theory. But you are accepting the risk that from time to time all > your vtapes will be 100% full and you will not have enough space on your > disk. And I don't think there is any provision in Amanda to prevent > that.
Do you really expect all (or most) of your vtapes to be 100% full? If so, I do not think you have allocated enough total space. Amanda has one provision for dealing with such situations, the holding disk. Mine is dedicated, and about the size of four vtapes. Another is "runtapes". Oh, or do you plan to run exactly the number of vtapes that you need for your chosen dumpcycle? > > So I prefer to stick with the amount of vtapes equal to the real amount > of disk space. Then, from my experience, you will be leaving about 1/3 of your disk empty. > > The answer to that is, "that depends". I have tried to have a vtape > > size a bit larger than my typical daily backup, and then allow amanda > > to use enough extra tapes to cover the largest likely backup. So most > > days I use one vtape, 40-90% filled. Some days I use three or four > > vtapes. All but the last are almost 100% filled. You can also play > > with your split size. My runs mirror Charles' exactly. I also configure my DLEs' dumpcycles according to the data. Unchanging data (music, photos) get 1 month cycles, other stuff 1 or 2 weeks. > I don't think that depends at all unless you have a very deterministic > usage patern. When the size of the daily backup is truly random, it > becomes a purely mathematical problem: Is your backup size really even pseudo random? Mine, over 40+ years, at many sites, have never been. > Each day, you are wasting on average 1/2 vtape amount of disk. So you > could have vtape being half the size of what you are using, wasting 1/4 > of the initial amount, ... That is based on the assumption that your tapes match the available space and your runtapes is 1. Neither of which ?we?/I recommend. BTW I just peeked, my disks dedicated to vtapes, even though substantially over- subscribed are between 79% and 89% full. > ... but then you are wasting x blocks overheard for declaring new > directories and using more inodes. When do both fucntions cross? First, though an unused inode would be allocated, no inodes would be wasted. When you create your file system (assuming extX, ???) space to a set number of inodes is created. Second, disks have many millions, even billions of data blocks. Are you really worried about using another 1 or 3 for a directory? You must have more important thing with which to be concerned. One last thing, when you create your file system(s) for vtapes you may be able to control how many inodes are created. Remember each file takes only one inode. A 3TB disk of vtapes on my system only has a total of 947 files. Yet there were 350,000 inodes created even though I changed the mkfs options to greatly reduce them. Another disk where I forgot to reduce the number of inodes created has 190,000,000 inodes. So I'm "wasting" about 20,000,000 data blocks as inodes. Not enough for a 100GB vtape, but enough for four 5GB chunks. -- Jon H. LaBadie j...@jgcomp.com 11226 South Shore Rd. (703) 787-0688 (H) Reston, VA 20190 (703) 935-6720 (C)
