16 ms·
Note that if you're using Ubuntu you're using ureadhaead, which does something similar to minimize seeks during boot. https://wiki.archlinux.org/index.php/Urea
by sciurus 14y ago
Note that if you're using Ubuntu you're using ureadhaead, which does something similar to minimize seeks during boot.
https://wiki.archlinux.org/index.php/Ureadahead https://wiki.archlinux.org/index.php/Ureadahead
- rcthompson 14y agoThen why are there deb files for Ubuntu? I don't think they're doing exactly the same thing, since e4rat is using specific features of the Ext4 filesystem. Edit: Actually, the directions say to remove Ureadahead when installing e4rat, so maybe they are quite similar.
- yason 14y agoAFAIK, ureadahead just keeps track of which files/blocks are touched during bootup/startx and pre-reads them into a cache at the very beginning of the boot sequence so you will effectively boot from cache. This still requires seeking to several semi-random areas of the disk while prereading which e4rat is fixing by physically moving the needed blocks adjacent to eachother.
- deleted 14y ago[deleted]
- sciurus 14y agoFor some reason, I had the idea that ureadahead's pack files actually contained the contents of the blocks that needed to be read during boot, turning readahead into a sequential operation. After reading the manpage today, I see that I was mistaken.
- ntoshev 14y agoIt would be nice if someone installed e4rat on Ubuntu (with ureadahead) and reported the performance.
- obtu 14y agoSince ureadahead looks at blocks and not files, it has a potential speed advantage if the boot process is opening some large files but not reading them in full. Edit: except the ureadahead packfile only points to the blocks and files, it does not provide a way to inline them. So e4rat is almost certainly faster. It's a shame it is ext4 specific. Apparently Scott James Remnant, the ureadahead developer, considered feeding the collected info to a defragmenter: http://ubuntuforums.org/showthread.php?t=1434502 http://ubuntuforums.org/showthread.php?t=1434502 ; this would be nice, as it means a single package is responsible for the feature, and filesystems perform to the best of their ability whether or not they have ext4-like fine-grained control of defragmentation.
- rcthompson 14y agoSo it sounds like the filesystem-reorganizing features of e4eat (but not the profiling features) would be complementary to ureadahead.