Messages in this thread | | | Subject | Re: 3.0 wishlist Was: Overview of 2.2.x goals? | From | Viet-Trung Luu <> | Date | Thu, 22 Jan 1998 00:51:57 -0500 (EST) |
| |
Stefan Monnier wrote: > Brad Keryan <keryan@andrew.cmu.edu> writes: > > Log-structured filesystems sound extremely good on paper. Is there a > > stable, fast, log-structured filesystem for any OS at this point? > > AIX's LFS, IRIX's XFS, Digital Unix's AdvFS. These are pretty fast and stable. > WinNT's NTFS is supposed to be log-structured too and reasonably stable (don't > know about speed, but making anything fast within WinNT is not easy). > > SunOS's ufs has also been hacked by adding a log to it. I don't know if it's > fast and/or stable, though. > > Of course, there's also BSD's LFS, but I don't know if it's stable in any > current BSD derivative.
Doesn't AIX use "JFS"? In any case, JFS, XFS, AdvFS, and NTFS are "journalling" (they log meta-data changes, and possibly other things, but that's *separate* from the main structure of the FS), not log-structured.
BSD's LFS is log-structured -- everything is appended to a log, so blocks and inodes move around... *all* writes are done at the "end" ("tail"?) of the log.
In any case, log-structured FSes pay a large performance penalty whenever they have to go and actually do a read off disk (for most systems, it's probably an overall win, but for some, it could be a big loss).
I don't know of any other log-structured FS, though. Network Appliance's WAFL (used on their FAServers) is incredibly cool (but probably complicated). See http://www.netapp.com/technology/level3/3002.html.
- Trung
| |