On Tuesday, May 22, 2012 at 2:04 AM, Jerker Nyberg wrote: > On Mon, 21 May 2012, Gregory Farnum wrote: > > > This one the write is considered "safe" once it is on-disk on all > > OSDs currently responsible for hosting the object. > > > > Is it possible to configure the client to consider the write successful > when the data is hitting RAM on all the OSDs but not yet committed to > disk? Direct users of the RADOS object store (i.e., librados) can do all kinds of things with the integrity guarantee options. But I don't believe there's currently a way to make the filesystem do so — among other things, you're running through the page cache and other writeback caches anyway, so it generally wouldn't be useful except when running an fsync or similar. And at that point you probably really want to not be lying to the application that's asking for it. > Also, the IBM zFS research file system is talking about cooperative cache > and Lustre about a collaborative cache. Do you have any thoughts of this > regarding Ceph? I haven't heard of this before, but assuming I'm understanding my brief read directly, this isn't on the current Ceph roadmap. I sort of see how it's useful, but I think it's less useful for a system like Ceph — we're more scale-out in terms of CPU and memory correlating with added disk space compared to something like Lustre where the object storage (OST) and the object handlers (OSS) are divorced, and we stripe files across more servers than I believe Lustre tends to do. But perhaps I'm missing something — do you have a use case on Ceph? -Greg -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
