On 11/13/2010 09:03 PM, Pete Zaitcev wrote:
On Fri, 12 Nov 2010 13:14:45 -0500
Jeff Darcy<jdarcy(a)redhat.com> wrote:
> As mentioned in the IRC meeting yesterday, I've put together a CloudFS
> feature proposal at https://fedoraproject.org/wiki/Features/CloudFS
> Feedback would be most welcome.
I have a question: why not adopt Ceph instead?
Why does either have to be adopted *instead* of the other? They're both
admirable pieces of work, with slightly different strengths. The
technology in Ceph (e.g. RADOS, CRUSH) is slightly more advanced, and it
would generally be a great choice for anyone looking for a solution in
the traditional distributed-filesystem space. On the other hand, when
it comes to a *cloud* filesystem specifically and the features that
implies, I think the modular architecture of GlusterFS carries much
greater weight. That provides several significant advantages.
* It allows functionality to be added without perturbing a core which
many users already depend on.
* It moves functionality out to where needed library support (e.g. for
auth/crypto) already exists, without tedious interfaces and brittle
coupling between kernel and user-space components (e.g. mountd, lockd,
* It moves functionality with high memory requirements (e.g. maintaining
long "patch" lists for multi-site replication) or long sequential
control flows out of the kernel where such things don't belong.
* It accelerates development by avoiding the endless churn in the VFS
and block layers, and by making more development tools available.
I'd estimate that development for something like multi-site replication
would take two to four times as long on a Ceph base, so I'd be proposing
it as a feature for Fedora 18 instead. ;) Even if the goal were to
implement CloudFS in the kernel eventually, I'd do it in user space
first to get all the protocol stuff sorted out before dealing with
low-level implementation issues. I have every intention to continue
supporting and recommending both Ceph and GlusterFS/CloudFS for their
respective use cases, as I consider them quite complementary.