> Now what would be cool is a journaled file system for bsd. Any one out > there? Perhaps when bsd supports xfs, reiser or ext3.
I think soft dependences is basically BSD's answer to journaling. Here's an exerpt from the NetBSD FAQs - http://netbsd.org/Documentation/misc/ : --- Q Are there any measured improvements of softdep? (top) The fact that meta-data isn't immediately written to disk makes the system feel a lot faster. No numbers are available to show this at this moment. Paul Vixie has run a benchmark on storing and retrieving (in random order) 75.000 files into a directory, on both a system with and without softdep. The results show that file access time for both creating and locating files in large directories are generally better on systems with soft dependencies. (The softdep system in this case was FreeBSD 4.2, the non-softdep system was BSD/OS 3.1. Similar behaviour will be visible on a NetBSD system with and without softdep). Q How resilient is the Fast File System (FFS), FFS with softdeps and NetBSD's ext2fs implementation with respect to unclean shutdowns? (top) The FFS takes care to correctly order all metadata operations, as well as to ensure that all metadata operations precede operations on the data to which they refer, so that the file system may be guaranteed to be recoverable after a crash. The last N seconds of file data may not be recoverable, where N is the syncer interval, but the file system metadata will be. N is usually 30. With softdeps running, you've got almost the same guarantee. With softdeps, you have the guarantee that you will get a consistent snapshot of the file system as it was at some particular point in time before the crash. So you don't know, as you did without softdeps, that, for example, if you did an atomic operation such as a rename of a lock file, the lock file will actually be there; but you do know that the directory it was in won't be trashed and you do know that ordering dependencies between that atomic operation and future atomic operations will have been preserved, so if you are depending on atomic operations to control, say, some database-like process (e.g. writing mail spool files in batches, gathering data from a transaction system, etc.) you can safely start back up where you appear to have left off. NetBSD's ext2fs implementation gives you the traditional FFS guarantee about metadata (unlike the Linux implementation), so you can actually use it with more confidence than you can use the native ext2fs in Linux. The downside is that it's a bit slower, but that's because it actually does the right thing if the system crashes, instead of potentially eating your file system itself. --- Maybe someone more knowledgeable than I can comment on what "the right thing" is refering to in that last paragraph. In addition to using softdep one can mount portions of their system on a memfs - basically a RAM disk. For a modern single-user system with lots of memory this seems like it would be ideal, especially if using ECC memory. Ref: NetBSD Tuning: http://netbsd.org/Documentation/tune/5.html -Beaker P.S. Thanks Neil - your last post regarding file descriptors answered my question as to how fd3-19 get "defined". -- [ SiMpLe MaChInEs ] --> gopher://beaker.mdns.org or (via proxy) http://gopher.floodgap.com/gopher/gw.lite?gopher://beaker.mdns.org:70/1 _______________________________________________ EuG-LUG mailing list [EMAIL PROTECTED] http://mailman.efn.org/cgi-bin/listinfo/eug-lug
