On Mon, Feb 7, 2011 at 2:54 PM, Nico Williams <n...@cryptonector.com> wrote:
> On Mon, Feb 7, 2011 at 1:49 PM, Yi Zhang <yizhan...@gmail.com> wrote:
>> Please see my previous email for a high-level discussion of my
>> application. I know that I don't really need O_DSYNC. The reason why I
>> tried that is to get the side effect of no buffering, which is my
>> ultimate goal.
>
> ZFS cannot not buffer. The reason is that ZFS likes to batch transactions
> into
> as large a contiguous write to disk as possible. The ZIL exists to
> support fsyn(2)
> operations that must commit before the rest of a ZFS transaction. In
> other words:
> there's always some amount of buffering of writes in ZFS.
In that case, ZFS doesn't suit my needs.
>
> As to read buffering, why would you want to disable those?
My application manages its own buffer and reads/writes go through that
buffer first. I don't want double buffering.
>
> You still haven't told us what your application does. Or why you want
> to get close
> to the metal. Simply telling us that you need "no buffering" doesn't
> really help us
> help you -- with that approach you'll simply end up believing that ZFS is not
> appropriate for your needs, even though it well might be.
It's like the Berkeley DB on a high level, though it doesn't require
transaction support, durability, etc. I'm measuring its performance
and don't want FS buffer to pollute my results (hence directio).
>
> Nico
> --
>
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
