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On Jan 20, 2006 23:10 -0800, Andrew Morton wrote: > Andreas Dilger <adilger@clusterfs.com> wrote: > > > > On Jan 18, 2006 22:06 +0900, Takashi Sato wrote: > > > As a disk tends to get large, a disk storage has had a capacity to > > > supply multi-TB. But now, ext3 can't support more than 8TB filesystem > > > when blocksize is 4KB. That's why I think ext3 needs to be > > > more than 8TB. > > > > > > Therefore I think filesystem size can increase on architectures > > > which has more than 4KB pagesize by extending blocksize to pagesize on > > > ext3. For example, the following is in case of ia64. (Blocksize have > > > already been supported up to pagesize on ext2. Why is the max blocksize > > > restricted to 4KB on ext3?) > > > > > > Max filesystem size on ia64: > > > Original :4096(blocksize) * 2^31 = 8TB > > > After modification [pagesize=16KB(default)]:16384(blocksize) * 2^31 = 32TB > > > After modification [pagesize=64KB(max)] :65536(blocksize) * 2^31 = 128TB > > > > Just for others' info - the fill_super change has been tested in the past > > by Sonny Rao at IBM also. e2fsprogs has supported this for a long time > > already. > > I have a vague memory that there's some piece of metadata (per-block-group > info, I think) which will overflow at 8kb blocksize. I say this in the > hope that you'll remmeber what it was ;) This is the group descriptor per-group blocks and inode free counts. The current mke2fs code limits the number of blocks and inodes per group to EXT2_MAX_BLOCKS_PER_GROUP (2^16 - 8) and (2^16 - EXT2_INODES_PER_BLOCK) so that this won't overflow. We still get linear growth of filesystem limits with blocksize, but not cubic growth that would otherwise be there. Bull has a patch which enlarges the group descriptor fields to allow more blocks and inodes per group. > I've rewritten ext3 directory readahead to use the generic pagecache > functions, so changes here shouldn't be needed. > > But I haven't yet got around to performance-testing it. > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.16-rc1/2.6.16-rc1-mm2/broken-out/ext3_readdir-use-generic-readahead.patch Hmm, I'll have to take a look at that when I get a chance. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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