delayed file deallocation?

[Isaac Claymore <clay@exavio.com.cn>]

Hi list,

We're using reiser 3.6 as workhorse fs beneath Samba in our NAS setup.
Under our workload, it's common that tens of clients (often around 20)  
are doing real-time video editing simultaneously. We've been suffering a
scenario that when one client comes and deletes some large file while
many others are busy editing, the many others will experience noticeable
period of IO stalling, usually of about 3 seconds. And, since they're
doing some kind of realtime editing, this stall is unacceptable.

I'm wondering that whether the file deallocation could be delayed
somewhat, i.e. when a file is unlink()'ed by Samba, fs driver just mark
the file to-be-deallocated when its reference count reaches zero. Then,
the fs driver, at some later time, either triggered by user space or when 
lack of free space, actually commits the deallocation. Since we have
plenty of free disk space, this deallocation scheme does make sense.

It's possible to do this in user space, say, by modifying Samba so that
it creates an extra secret link to each file it creates, and write
another program that routinely checks the secret links, at proper times,
for those inodes with inode ref count of 1, and unlinks them.

But for some reason, we do not want to touch Samba code, then it looks that
this can only be done at fs level.

How can I achieve this with Reiser? Or, if you've some alternatives,
please kindly enlighten me.

Thanks for any hint or suggestion.


-- 

Regards, Isaac
()  ascii ribbon campaign - against html e-mail
/\                        - against microsoft attachments