From mboxrd@z Thu Jan 1 00:00:00 1970 From: ron minnich To: 9fans@cse.psu.edu Subject: Re: [9fans] boot error walking In-Reply-To: <00a701c3f2cd$11e93720$8201a8c0@cc77109e> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Date: Sat, 14 Feb 2004 08:45:42 -0700 Topicbox-Message-UUID: e3bace04-eacc-11e9-9e20-41e7f4b1d025 On Sat, 14 Feb 2004, Bruce Ellis wrote: > often kfs is enough. and it co-exists with fossil/venti. venti > fkd over a few of my files last week. some scrambled > message about a mismatch obscured by other windows > being updated. fortunately i could recreate both of them > easy. a pity if had been /bin/rc. > > i think there are some concurrency issues (in f/v). Was it venti that really did that? Or was it some f/v miscommunication? I no longer trust fossil after my last experience, but I do trust venti. Venti saved my neck. It seems from what I read here and have experienced that venti is rock solid, fossil less so. If you're telling me venti is also less solid, then I'm worried. Maybe it's time to just revive kfs with long file names. For me anyway, a file system is not a real file system until (at least) you can cycle power in the middle of each and every operation without ill effects, recovery is comprehensible and complete, and finally improper operation (e.g. letting the disk fill up) should not result in an unbootable machine. By these standards fossil is a very interesting experiment but not exactly a file system; it has a long way to go to equal what I'm used to in the Unix/Linux world. It's quite nice, with the snapshots etc., but not to be trusted. People tell me fossil is ok if you treat it nice, but in the real world I want to be able to be mean to the file system and have it survive anyway. Venti on the other hand, based on everything I've seen, is to be trusted. I hope that is true. The concurrency point is interesting. Another thing I wonder about is order of operations. Fossil is a set of processes. Most file systems I've worked with depend on controlling the ordering of disk writes for data vs. metadata I/O. "Smart" disk drives that reorder disk writes have been known to play havoc with file systems. I keep wondering if the kinds of guarantees on I/O ordering that a file system needs for its activities can be met outside a kernel? It just seems easy for fossil to get confused about what is where and when, and then all is lost. Just wondering. ron