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

[Amit Gud <gud@ksu.edu>]

Alan Cox wrote:
>> Preventive measures are taken to limit only one continuation inode per 
>> file per chunk. This can be done easily in the chunk allocation 
>> algorithm for disk space. Although I'm not quite sure what you mean by 
> 
> How are you handling the allocation in this situation, are you assuming
> that a chunk is "out of bounds" because part of a file already lives on
> it or simply keeping a single inode per chunk which has multiple sparse
> pieces of the file on it ?
> 
> ie if I write 0-8MB to chunk A and then 8-16 to chunk B can I write
> 16-24MB to chunk A producing a single inode of 0-8 16-24, or does it have
> to find another chunk to use ?

Hello Alan,

You re-use the same inode with multiple sparse pieces.

This way you avoid hopping around continuation inodes and coming back to 
same chunk with which you started but this time on a different 
continuation inode. This may not be I/O intensive for successive 
traversals if the continuation inodes are pinned in the memory, but it 
certainly is a waste of resource - inodes. Not allowing this would make 
worst case of every file having a continuation inode in every chunk, 
even worse; may be like only single file exist in the file system and 
rest all inodes in all chunks (including file's own chunk) are 
continuation inodes.


AG
-- 
May the source be with you.
http://www.cis.ksu.edu/~gud