Date: Thu, 29 Sep 2005 19:17:44 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: dougb@FreeBSD.org Cc: freebsd-hackers@FreeBSD.org, aanton@smtpx.spintech.ro, mwm@mired.org Subject: Re: journaling fs and large mailbox format Message-ID: <200509300217.j8U2HioU009196@gw.catspoiler.org> In-Reply-To: <433C6D51.8020409@FreeBSD.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On 29 Sep, Doug Barton wrote: > Mike Meyer wrote: >> A 4K block won't hold your median file. But an 8K block wastes a lot of >> space. You might get a file with 0 blocks and 3 frags, assuming that UFS2 >> will do that, which doesn't seem good. If UFS2 won't do that, you get a >> lot of half-empty blocks, which likewise isn't good. The other option is >> a 4K block size, which means you get a lot of 1 block + 1 frag files. >> That seems optimal in this case. > > That's a logical analysis, but you're missing one important premise. UFS > doesn't do "more than one file per frag" until the file system gets close to > filling up, and the optimization switches from time to space. Therefore, in > your example you're actually wasting more space than you would with 8k > blocks, and as a side effect making the fs less efficient in at least 2 ways. If you know that most of the files are write-once and don't grow over time, you can tune the file system to always do space optimization. I used to do this with classic Usenet spools and it worked well.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200509300217.j8U2HioU009196>