On Mon, 18 Nov 2019 13:13:00 +0700 Olivier <[email protected]> wrote:
> I am wondering what is the best size to declare for the lenght of the > vtapes. Too long a vtape could lead to disk space being unused, You may have a misconception here. Vtapes emulate physical tapes, but not in all respects. If you don't fill up a tape, that unused space is gone. But if you don't fill up a vtape, it simply means there is that much space available for other files, such as other vtapes. 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. > but > having too many small vtapes one or two directories created for each > new vtape, and if many vtapes, the main directory containing them > would not fit in a single inode; but the space left unused would be > smaller. > > My understanding is that splitting a backup does not consume more > space, so it is not the backup data that gets bigger, only what is > surrounding it. > > If wee are not considering the overhead of computing the tape > spliting, nor the possible extra I/O, if we only focus on the disk > space, what would be the optimum size for the vtapes? 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. I suggest you do the rough calculations to get your initial setup, then fiddle with it as you gain experience and as amanda settles its calculations down over time. -- Does anybody read signatures any more? https://charlescurley.com https://charlescurley.com/blog/
