Re: [RFC][PATCH] ChunkFS: fs fission for faster fsck

Suparna Bhattacharya
2007-04-23T16:26:43Z

On Mon, Apr 23, 2007 at 09:58:49PM +0530, Suparna Bhattacharya wrote:
> On Mon, Apr 23, 2007 at 06:21:34AM -0500, Amit Gud wrote:
> >
> > This is an initial implementation of ChunkFS technique, briefly discussed
> > at: http://lwn.net/Articles/190222 and
> > http://cis.ksu.edu/~gud/docs/chunkfs-hotdep-val-arjan-gud-zach.pdf
> >
> > This implementation is done within ext2 driver. Every chunk is an
> > independent ext2 file system. The knowledge about chunks is kept within
> > ext2 and 'continuation inodes', which are used to allow files and
> > directories span across multiple chunks, are managed within ext2.
> >
> > At mount time, super blocks for all the chunks are created and linked with
> > the global super_blocks list maintained by VFS. This allows independent
> > behavior or individual chunks and also helps writebacks to happen
> > seamlessly.
> >
> > Apart from this, chunkfs code in ext2 effectively only provides knowledge
> > of:
> >
> > - what inode's which block number to look for, for a given file's logical
> > block number
> > - in which chunk to allocate next inode / block
> > - number of inodes to scan when a directory is being read
> >
> > To maintain the ext2's inode number uniqueness property, 8 msb bits of
> > inode number are used to indicate the chunk number in which it resides.
> >
> > As said, this is a preliminary implementation and lots of changes are
> > expected before this code is even sanely usable. Some known issues and
> > obvious optimizations are listed in the TODO file in the chunkfs patch.
> >
> > http://cis.ksu.edu/~gud/patches/chunkfs-v0.0.8.patch
> > - one big patch
> > - applies to 2.6.18
>
>
> Could you send this out as a patch to ext2 codebase, so we can just look
> at the changes for chunkfs ? That might also make it small enough
> to inline your patch in email for review.

Sorry, I missed the part about ext2-chunkfs-diff below.

Regards
suparna

>
> What kind of results are you planning to gather to evaluate/optimize this ?
>
> Regards
> Suparna
>
> >
> > Attached - ext2-chunkfs-diff.patch.gz
> > - since the code is a spin-off of ext2, this patch explains better what
> > has changed from the ext2.
> >
> > git://cislinux.cis.ksu.edu/chunkfs-tools
> > - mkfs, and fsck for chunkfs.
> >
> > http://cis.ksu.edu/~gud/patches/config-chunkfs-2.6.18-uml
> > - config file used; tested mostly on UML with loopback file systems.
> >
> > NOTE: No xattrs and xips yet, CONFIG_EXT2_FS_XATTR and CONFIG_EXT2_FS_XIP
> > should be "no" for clean compile.
> >
> >
> > Please comment, suggest, criticize. Patches most welcome.
> >
> >
> > Best,
> > AG
> > --
> > May the source be with you.
> > http://www.cis.ksu.edu/~gud
>
>
>
> --
> Suparna Bhattacharya (suparna@in.ibm.com)
> Linux Technology Center
> IBM Software Lab, India
>

--
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India