On Feb. 16, 2009, 17:50 +0200, James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 2009-02-16 at 06:05 -0500, Jeff Garzik wrote: >> Boaz Harrosh wrote: >>> No can do. exofs is meant to be a reference implementation of a pNFS-objects >>> file serving system. Have you read the spec of pNFS-objects layout? they define >>> RAID 0, 1, 5, and 6. In pNFS the MDS is suppose to be able to write the data >>> for its clients as NFS, so it needs to have all the infra structure and knowledge >>> of an Client pNFS-object layout drive. >> Yes, I have studied pNFS! I plan to add v4.1 and pNFS support to my NFS >> server, once v4.0 support is working well. >> >> >> pNFS The Theory: is wise and necessary: permit clients to directly >> connect to data storage, rather than copying through the metadata >> server(s). This is what every distributed filesystem is doing these >> days -- direct to data server for bulk data read/write. >> >> pNFS The Specification: is an utter piece of shit. I can only presume >> some shady backroom deal in a smoke-filled room was the reason this saw >> the light of day. >> >> >> In a sane world, NFS clients would speak... NFS. >> >> In the crazy world of pNFS, NFS clients are now forced to speak NFS, >> SCSI, RAID, and any number of proprietary layout types. When will HTTP >> be added to the list? :) > > Heh, it's one of the endearing faults of the storage industry that we > never learn from our mistakes ... particularly in storage protocols. > > Actually, perhaps that's a mischaracterised: we never actually learn > from our successes. For example, most popular storage protocols solve > about 80% of the problem (NFSv2) get something bolted on to take that to > 95% (locking) and rule for decades. We end up obsessing about the 5% > and produce something that's like 10x the overhead to solve it. > Customers, for some unfathomable reason, hate complexity (I suspect > principally because it in some measure equals expense) so the 100% > solution (which actually turns out to be a 95% one because the over > engineered complexity adds another 5% of different problems that take > years to find) tends to work its way into a niche and stay there ... > eventually fading. > > If you're really lucky, the niche evolves into something sustainable. > For example iSCSI: blew its early promise, pulled a bunch of unnecessary > networking into the protocol and ended up too big to fit in disk > firmware (thus destroying the ability to have a simple network tap to > replace storage fabric). It's been slowly fading until Virtualisation > came along. Now all the other solutions to getting storage into virtual > machines are so horrible and arcane that iSCSI looks like a winner (if > the alternative is Frankenstein's monster, Grendel's mother suddenly > looks more attractive as a partner). > > So, trust the customer ... if it's so horrible it shouldn't have seen > the light of day, the chances are that no-one will buy it anyway. I completely agree with this sentence. And no customer, whatsoever, that I've talked to about pNFS had any reservations about supporting multiple layout types. On the contrary... Benny > > James > > > -- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
