Hello, Le Lundi 06 Février 2006 19:50, Duncan a écrit : > Fragmentation doesn't tend to be as much of an issue on Linux, with "real" > filesystems, as on MSWormOS, particularly FAT/FAT32. I'm running all > reiserfs here, FWIW. It doesn't have a compaction tool (defrag, on > MSWormOS), but I've not noticed any issues as a result.
Fragmentation seems to be a myth for anyone on Linux, and I was enclined to believe that myth until I started to use Gentoo. At first, a brand new gentoo system is fast, but after a few months and a dozen emerge -uDN world, things tend to slow down to a point that is barely acceptable. In fact, the first time I tought that maybe I installed too many things, and that my system was crippled with cruft. But then I had to repartition my hard drive, so I made a backup (tar zcvpf) of my different partitions, fdisk, mkfs, and tar zxvpf. The system was exactly the same as before, just the partition size had changed. But then emerge -S was much faster than before the operation, as well as common portage operations. Since then, I've tried to do the same on several servers, without the fdisk operation, just tar cp, mkfs, tar xp, and I've always noticed an appreciable speedup. The only explanation that comes from this experiment is fragmentation. And I think Gentoo is more sensible to fragmentation than binary distributions because it has to deal with many small files, often changing, during compilation and rsynchronisation. So the directories sensible to fragmentation are IMHO, /var/tmp and /usr/portage, and they are the ones to put on different partitions. Now, I don't have exact numbers to prove my sayings, but anyone can make the test themself, if they already have /var/tmp and/or /usr/portage on separate partitions. I didn't have time yet to sort out what kind of filesystem is more or less sensible to fragmentation, but from my experience, ext[23] is not a good candidate for /var/tmp or /usr/postage. Reiser3 has proven to fragment too, and one of the last system I installed was formated with XFS, which I will "defragment" in a few weeks. Hopefully I could then come with numbers. BTW, does someone know of a tools to show the fragmentation level of a *nix filesystem ? David -- gentoo-amd64@gentoo.org mailing list
