Messages in this thread | | | Date | Fri, 02 Aug 2002 19:10:30 +0400 | From | Hans Reiser <> | Subject | Re: BIG files & file systems |
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There are a number of interfaces that need expansion in 2.5. Telldir and seekdir would be much better if they took as argument some filesystem specific opaque cookie (e.g. filename). Using a byte offset to reference a directory entry that was found with a filename is an implementation specific artifact that obviously only works for a ufs/s5fs/ext2 type of filesystem, and is just wrong.
4 billion files is not enough to store the government's XML databases in.
Hans
Steve Lord wrote:
>On Fri, 2002-08-02 at 08:56, Jan Harkes wrote: > > >>I was simply assuming that any filesystem that is using iget5 and >>doesn't use the simpler iget helper has some reason why it cannot find >>an inode given just the 32-bit ino_t. >> >> > >In XFS's case (remember, the iget5 code is based on XFS changes) it is >more a matter of the code to read the inode sometimes needing to pass >other info down to the read_inode part of the filesystem, so we want to >do that internally. XFS can have 64 bit inode numbers, but you need more >than 1 Tbyte in an fs to get that big (inode numbers are a disk >address). We also have code which keeps them in the bottom 1 Tbyte >which is turned on by default on Linux. > > > >>This is definitely true for Coda, we have 96-bit file identifiers. >>Actually my development tree currently uses 128-bit, it is aware of >>multiple administrative realms and distinguishes between objects with >>FID 0x7f000001.0x1.0x1 in different administrative domains. There is a >>hash-function that tries to map these large FIDs into the 32-bit ino_t >>space with as few collisions as possible. >> >>NFS has a >32-bit filehandle. ReiserFS might have unique inodes, but >>seems to need access to the directory to find them. So I don't quickly >>see how it would guarantee uniqueness. NTFS actually doesn't seem to use >>iget5 yet, but it has multiple streams per object which would probably >>end up using the same ino_t. >> >>Userspace applications should either have an option to ignore hardlinks. >>Very large filesystems either don't care because there is plenty of >>space, don't support them across boundaries that are not visible to the >>application, or could be dealing with them them automatically (COW >>links). Besides, if I really have a trillion files, I don't want 'tar >>and friends' to try to keep track of all those inode numbers (and device >>numbers) in memory. >> >>The other solution is that applications can actually use more of the >>information from the inode to avoid confusion, like st_nlink and >>st_mtime, which are useful when the filesystem is still mounted rw as >>well. And to make it even better, st_uid, st_gid, st_size, st_blocks and >>st_ctime, and a MD5/SHA checksum. Although this obviously would become >>even worse for the trillion file backup case. >> >> > >If apps would have to change then I would vote for allowing larger >inodes out of the kernel in an extended version of stat and getdents. >I was going to say 64 bit versions, but if even 64 is not enough for >you, it is getting a little hard to handle. > >Steve > > > >>Jan >> >>
-- Hans
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