2014-06-21 1:48 GMT+08:00 Kai Krakow <hurikha...@gmail.com>: > microcai <micro...@fedoraproject.org> schrieb: > >> rsync is doing bunch of 4k ramdon IO when updateing portage tree, >> that will kill SSDs with much higher Write Amplification Factror. >> >> >> I have a 2year old SSDs that have reported Write Amplification Factor >> of 26. I think the only reason is that I put portage tree on this SSD >> to speed it up. > > Use a file system that turns random writes into sequential writes, like the > pretty newcomer f2fs. You could try using it for your rootfs but currently I > suggest just creating a separate partition for it and either mount it as > /usr/portage or symlink that dir into this directory (that way you could use > it for other purposes, too, that generate random short writes, like log > files). > > Then, I'd recommend changing your scheduler to deadline, bump up the io > queue depth to a much higher value (echo -n 2048 > > /sys/block/sdX/queue/nr_requests) and then change the dirty io flusher to > not run as early as it usually would (change vm.dirty_writeback_centisecs to > 1500 and vm.dirty_expire_centisecs to 3000). That way the vfs layer has a > chance to better coalesce multi-block writes into one batch write, and f2fs > will take care of doing it in sequential order. > > I'd also suggest not to use the discard mount options and instead create a > cronjob that runs fstrim on the SSD devices. But YMMV. > > As a safety measure, only ever partition and use only 70-80% of your SSD so > it can reliably do its wear-leveling. It will improve lifetime and keep the > performance up even with filled filesystems. > > --
many thanks to all of you! no I've put my portage tree on an F2FS partation now.
