Date: Sun, 4 Oct 1998 20:50:03 -0400 (EDT) From: "Mr. K." <bsd@the.nu> To: freebsd-fs@FreeBSD.ORG Subject: Re: efficient filesystem (fwd) Message-ID: <Pine.BSF.4.02A.9810042049270.20218-100000@the.nu>
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On Mon, 5 Oct 1998, Terry Lambert wrote: > > Do the directory breakout shuffle. Without something like VxVS (Veritas > > Filesystem, not available for non-commercial OSen unfortunately), which has > > some sort of hashed directory structure if I understand it right, then you are > > Actually, VxFS's directory code is lifted, pretty much verbatim, from > the AT&T UFS (FFS) implementation. It has AT&T Copyrights all over > the sources. > perhaps this is an old version you were looking at? http://compassion.qualix.com/sysman/product/vxvm.htmld/vsm-over.html "VxFS supports variable-length directory entries. Because file names may be very long, rather than allocate a directory entry at maximum size, wasting directory space and slowing access time, variable-length entries are used. However, these are less efficient to search than fixed-sized entries, because you cannot know where the next entry begins. To eliminate the need for a linear directory search, VxFS uses a hash table in each directory extent to locate directory entries quickly, accelerating file access." > What you need, if you are going to do something so silly as to have > a huge flat directory structure, is to implement a btree structured > directory, like OS/2 HPFS. > yes, I agree, and I was wondering if anyone had implemented something like this for freebsd. It's not worth it for me to implement it myself, and I'm not about to waste money on something commercial. Then again, if you're hacking on top of u/h/ffs, the hashing strategy is probably easier. I've also seen it done completely in the dnlc, which would keep complete compatibility, but it takes up memory and you have to load in all the data the first time you search each directory. > My advice is to not do this; instead you should break it down. > for now that's what I'll do but it's going to kludge up my cgi program and I'll have to scale it manually as I grow, so eventually I'll get to putting my files into a mysql database and have the webserver get the files from there. > The number of entries that have to be traversed to look up a directory > entry is 512 div (average_file_name_length + 24) * number of blocks. > > > Terry Lambert > terry@lambert.org > --- > Any opinions in this posting are my own and not those of my present > or previous employers. > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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