> Thinking about such feature in real world, I wonder how do you think > about this sceinario. > - user updates fileA ... fileZ, and aufs moves them down to /hdd (as > described above). > - but several files still exist on /ram. > - it means > + frequently used and larger files goes to /hdd > + less frequently used or smaller files are kept in /ram > > My point is "why do we keep those less frequently used files in /ram?" > I don't think that is what you want. The less frequently used files > should go to /hdd, and the more frequently used files should remain on > /ram I beleieve (of course as long as the size of /ram accepts them).
Yes, indeed. Using a ramdisk over an HDD is particularly beneficial in case of lots of small files because it eliminates seek time. > If (again _if_) aufs decides "how frequently this file is used" by its > atime or something, it may be possilbe to move the idle files down to > /hdd. Such move-down operation may be triggered by > - periodically (in time-line), or > - when the free space of /ram reaches the pre-specified watermark. Actually, I think determining which files are needed and which are not is not AuFS's job. There are several atime-based tools to determine temporary files that are not used anymore and delete them or move them away. I think exposing a mechanism for moving specified files to /hdd will be sufficient. An external daemon will monitor the ramdisk and request moving files that are not used to /hdd, thus making space for writing new files. Moving files back up on reading is not needed because the kernel caches frequently accessed files in RAM, and moving files up on writing is already supported (isn't it?). ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1
