Date: Fri, 17 May 1996 18:19:00 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: terry@lambert.org (Terry Lambert) Cc: kuku@gilberto.physik.rwth-aachen.de, freebsd-questions@freefall.freebsd.org Subject: Re: max filessystem size in FreeBSD 2.2? Message-ID: <199605172319.SAA04661@dyson.iquest.net> In-Reply-To: <199605172138.OAA20794@phaeton.artisoft.com> from "Terry Lambert" at May 17, 96 02:38:14 pm
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> > What is the maximum filesystem size? > > 2^63 or 9 * 10^18 bytes. There is a disklabel issue at 128G; > patches are available (yes, people are running with larger than 128G > FS's). > > The maximum single file size is on the order of 2^48 (~280G) because > of VM limitations. Ask John Dyson to be sure. > > Current VM limitations are probably due to the PAGE_SIZE being 4K, and we can have 32 bits of them. Whether it is 2GPages or 4GPages depends on my code signed/unsigned bogosity factor :-), or using the "right variable sizes." There is probably a limitation in vfs_bio (or other filesystem code) of 512Bytes for a block and we can have 32 bits of them. That would cause me to guess that at that layer we can probably do 1Tb (512*2GBlocks). Again, there might be a problem with using the "right size" of variables. There are other limitation that I have heard of, but those are the basic limitations of the above subsystems. It is possible to overcome them, and I would think that the vfs_bio limitation is worse. John
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