Date: Wed, 13 Jul 2005 21:30:07 -0500 From: Kevin Kinsey <kdk@daleco.biz> To: Tsampros Leonidas <ltsampros@upnet.gr> Cc: freebsd-questions@freebsd.org Subject: Re: mountmsdosfs(): disk too big still a problem? Message-ID: <42D5CE2F.6060104@daleco.biz> In-Reply-To: <20050714002046.GA13158@bifteki.lan> References: <20050713235705.GA12910@bifteki.lan> <20050714002046.GA13158@bifteki.lan>
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Tsampros Leonidas wrote: >On Wed, Jul 13, 2005 at 11:57:05PM +0000, Tsampros Leonidas wrote: > > >>>Alex Teslik wrote: >>> >>> >>> >>>>I have run into the "mountmsdosfs(); disk too big" problem while trying to >>>>mount a 250GB FAT32 drive. This problem is pretty well documented: >>>> >>>>http://www.atm.tut.fi/list-archive/freebsd-stable/msg11027.html >>>> >>>>but I couldn't find any documentation regarding it being fixed when I >>>>googled >>>>around. >>>>I am running FreeBSD 4.10-RELEASE-p5 i386. Does anyone know if this >>>>problem is >>>>fixed in 4.11 or 5.4? >>>> >>>> >>>> >>>> >>Recompile the kernel with >> >>options MSDOSFS_LARGE >> >>Works for me, 5.4-STABLE. >> >> > >Of course , you have to be careful with this one. From 5.3 Release >notes: > >The MSDOSFS_LARGE kernel option has been added to support FAT32 >file systems bigger than 128GB. This option is disabled by default. It >uses at least 32 bytes of kernel memory for each file on disk; >furthermore it is only safe to use in certain controlled situations, >such as read-only mount with less than 1 million files and so >on. Exporting these large file systems over NFS is not supported. > >>From cvs: > >date: 2004/07/03 13:22:38; author: tjr; state: Exp; lines: +23 -1 >popular request, add a workaround that allows large (>128GB or so) >FAT32 filesystems to be mounted, subject to some fairly serious limitations. > >This works by extending the internal pseudo-inode-numbers generated from >the file's starting cluster number to 64-bits, then creating a table >mapping these into arbitrary 32-bit inode numbers, which can fit in >struct dirent's d_fileno and struct vattr's va_fileid fields. The mappings >do not persist across unmounts or reboots, so it's not possible to export >these filesystems through NFS. The mapping table may grow to be rather >large, and may grow large enough to exhaust kernel memory on filesystems >with millions of files. > >Don't enable this option unless you understand the consequences. > > Thanks for including the warnings. To me, this basically means "this is not (well) supported yet" and that means I didn't consider it worth using or mentioning to the O.P. However, in reading the programmer's comments, it looks as if MSDOSFS_LARGE might be worth looking into as long as the data weren't too critical and the systems weren't huge... FAT32 still seems to be a good option for cross-platform USB mass storage, for example, as NTFS isn't really writable by FBSD either.... KDK
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