Jon LaBadie <j...@jgcomp.com> writes: > 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?
Of course not. runtapes can be as big as needed, provided that vtapes are small enough. >> 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. /dev/ada3p1 2.6T 2.2T 234G 91% /automnt/ada3 /dev/ada4p1 2.6T 2.3T 121G 95% /automnt/ada4 /dev/ada2p1 2.6T 2.4T 8.5G 100% /automnt/ada2 /dev/ada5p1 2.6T 2.4T 60G 98% /automnt/ada5 /dev/ada1p1 2.6T 2.0T 458G 82% /automnt/ada1 /dev/ada6p1 2.6T 2.3T 86G 97% /automnt/ada6 Disks are 3TB with 27 vtapes in each disk an 10GB per chunk. I am surprised at the 100% utilisation reported for ada2, even if it is "system utilisation" with some decent amount of space left. > Is your backup size really even pseudo random? Mine, over 40+ years, > at many sites, have never been. As I said, this is a theoretical exercise. The largest chuck of data that I backup every day is the users files, that can vary a lot when you have 200+ users. > 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. Runtapes could be bigger than needed, Amanda will use only what it needs. > 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. OK, my mistake for mentioning inodes. I would have to review how filesystems (ufs, FreeBSD) work. If creating a directpry does not consume any disk space, then there is no penalty for having a multitude of small vtapes. > 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. I have the same number of files per disk. > 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. I will have to remember twicking the filesystem the next time I change the disks, because with the default, I am wasting over 350 million inodes per disk. Thank you, Olivier --
