On Mon, Feb 04, 2008 at 11:44:31AM -0800, Linus Torvalds wrote: ... > Pure user-space solutions work, but tend to eventually be turned into > kernel-space if they are simple enough and really do have throughput and > latency considerations (eg nfsd), and aren't quite complex and crazy > enough to have a large impedance-matching problem even for basic IO stuff > (eg samba). ... > So just going by what has happened in the past, I'd assume that iSCSI > would eventually turn into "connecting/authentication in user space" with > "data transfers in kernel space". But only if it really does end up > mattering enough. We had a totally user-space NFS daemon for a long time, > and it was perfectly fine until people really started caring. I'd assumed the move was primarily because of the difficulty of getting correct semantics on a shared filesystem--if you're content with NFS-only access to your filesystem, then you can probably do everything in userspace, but once you start worrying about getting stable filehandles, consistent file locking, etc., from a real disk filesystem with local users, then you require much closer cooperation from the kernel. And I seem to recall being told that sort of thing was the motivation more than performance, but I wasn't there (and I haven't seen performance comparisons). --b. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
