Date: Sun, 27 Jan 2002 15:36:27 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Brad Knowles <brad.knowles@skynet.be> Cc: "Matthew D. Fuller" <fullermd@over-yonder.net>, Mike Meyer <mwm-dated-1012390758.50933b@mired.org>, chip <chip@wiegand.org>, freebsd-chat@freebsd.org Subject: Re: Bad disk partitioning policies (was: "Re: FreeBSDIntaller(was "Re: ... RedHat ...")") Message-ID: <3C548EFB.DAEBEFBD@mindspring.com> References: <20020123124025.A60889@HAL9000.wox.org> <3C4F5BEE.294FDCF5@mindspring.com> <20020123223104.SM01952@there> <p0510122eb875d9456cf4@[10.0.1.3]> <15440.35155.637495.417404@guru.mired.org> <p0510123fb876493753e0@[10.0.1.3]> <15440.53202.747536.126815@guru.mired.org> <p05101242b876db6cd5d7@[10.0.1.3]> <15441.17382.77737.291074@guru.mired.org> <p05101245b8771d04e19b@[10.0.1.3]> <20020125212742.C75216@over-yonder.net> <p05101203b8788a930767@[10.0.1.14]> <3C5345A0.68D0CE99@mindspring.com> <p05101206b879b58fa8d5@[10.0.1.14]>
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Brad Knowles wrote: > > 85% hash fill is 85% hash fill. > > > > If you have an arbitrary sized hash table, then why do you > > somehow think the probability of a hash collision goes down > > as the size of the hash table goes up, if the relative load > > on the hash table increases until it is the same percentage > > of the total hash table size? > > But this isn't my understanding of how the filesystem works. > If hash tables are used, they are only used locally, and elsewhere we > use a digraph. If this weren't the case, then we would have never, > ever had problems with directory size and storing many millions of > files in a single directory. The excerpt is an attempt to explain why it isn't just "common sense" that the amount of free reserve would not be proportional to the carrying capacity, rather than some small, fixed amount. It's not really directly applicable, unless you increase cylinder group size. > Yes, I realize that dirprefs and dirhash change this scenario > somewhat with more modern versions of FreeBSD, but I still don't > believe that they change the filesystem/inode behaviour to use a > global "perfect hash". You are correct. I think people should just read the papers. > > Please search for "perfect hash" in the NEC "Cite Seer" CS > > reference database. > > This is the first I've heard of this database. Can you provide an URL? Really?!? It's one of the most important CS resources on the web, IMO; the NCSTRL database is a poor second (but also important). Here's the top level URL: http://citeseer.nj.nec.com/ Here's the FFS reference, for example: http://citeseer.nj.nec.com/mckusick84fast.html -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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