Re: [LSF/MM ATTEND] Stackable Union Filesystem Implementation

[Saket Sinha <saket.sinha89@gmail.com>]

>> One of the big problems was that too many copyups were made on the
>> read-write file system. So we decided to implement an union file
>> system designed for diskless systems, with the following
>> functionalities:
>>
>> 1. union between only one read-only and one read-write file systems
>>
>> 2. if only the file metadata are modified, then do not
>> copy the whole file on the read-write files system but
>> only the metadata (stored with a file named as the file
>> itself prefixed by '.me.')
>   So do you do anything special at CERN so that metadata is often modified
> without data being changed? Because there are only two operations where I
> can imagine this to be useful:
> 1) atime update - but you better turn atime off for unioned filesystem
>    anyway.
> 2) xattr update
>
As already mentioned that the issue that we were facing was that "too
many copyups were made on the  read-write file system".
Writes to a file system in a  unioning file system will produce many
duplicated blocks in memory since it uses a stackable filesystem
approach so response time for a particular operation is also a
concern.

Regards,
Saket Sinha

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>