Re: du: cache directory size

[Pádraig Brady]

Pádraig Brady wrote:
> Mildred wrote:
>> Hi,
>>
>> I noticed that du takes a long time to scan directories and measure
>> disk usage.
>>
>> I was thinking that perhaps caching the size of directories could bu
>> useful. Perhaps, after du computes the size of a directory, it could
>> write its size in its extended attributes (if the filesystem support
>> it). Next time, du would only compare the directory atime (or mtime
>> perhaps) with the time of the scan. That could possibly save some time
>> during the scan.
> 
> Those values would be invalidated though once a change
> has been written anywhere in the tree under a directory.

I just noticed the announcement of the Ceph distributed file system
which does maintain tree sizes for each node:

http://lkml.org/lkml/2008/7/15/385