On Apr 25, 2012, at 2:26 PM, Paul Archer wrote: > 2:20pm, Richard Elling wrote: > >> On Apr 25, 2012, at 12:04 PM, Paul Archer wrote: >> >> Interesting, something more complex than NFS to avoid the >> complexities of NFS? ;-) >> >> We have data coming in on multiple nodes (with local storage) that is >> needed on other multiple nodes. The only way >> to do that with NFS would be with a matrix of cross mounts that would >> be truly scary. >> Ignoring lame NFS clients, how is that architecture different than what you >> would have >> with any other distributed file system? If all nodes share data to all other >> nodes, then...? >> -- richard >> > > Simple. With a distributed FS, all nodes mount from a single DFS. With NFS, > each node would have to mount from each other node. With 16 nodes, that's > what, 240 mounts? Not to mention your data is in 16 different > mounts/directory structures, instead of being in a unified filespace.
Unified namespace doesn't relieve you of 240 cross-mounts (or equivalents). FWIW, automounters were invented 20+ years ago to handle this in a nearly seamless manner. Today, we have DFS from Microsoft and NFS referrals that almost eliminate the need for automounter-like solutions. Also, it is not unusual for a NFS environment to have 10,000+ mounts with thousands of mounts on each server. No big deal, happens every day. On Apr 25, 2012, at 2:53 PM, Nico Williams wrote: > To be fair NFSv4 now has a distributed namespace scheme so you could > still have a single mount on the client. That said, some DFSes have > better properties, such as striping of data across sets of servers, > aggressive caching, and various choices of semantics (e.g., Lustre > tries hard to give you POSIX cache coherency semantics). I think this is where the real value is. NFS & CIFS are intentionally generic and have caching policies that are favorably described as generic. For special-purpose workloads there can be advantages to having policies more explicitly applicable to the workload. -- richard -- ZFS Performance and Training richard.ell...@richardelling.com +1-760-896-4422
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