Re: fsfs revprop packing in f5 Re: Does fsfs revprop packing no longer allow usage of traditional backup software?

Philip Martin <philip.martin_at_wandisco.com> writes:

> Holding the write lock will block readers so for better concurrency we
> want to minimise the time that a write lock is held, or have more locks.

Daniel pointed out that readers don't block, they simply read the pack
file and get either the old or atomically replaced new file. Thus there
is no need to minimise lock time for readers, and we can design the the
locks to minimise write IO. So we want the lock held for the whole
read/write/replace operation so that concurrent writers don't do IO that
has to be thrown away.

One lock per pack file will allow concurrent writes to different shards
and so would help with write concurrency if that is important.

-- 
uberSVN: Apache Subversion Made Easy
http://www.uberSVN.com