4 ms·

I used to work with a fairly large HPC environment which had a large number of NFS attached disks. One of the issues we ran into was unlink() on ext4; it could

I used to work with a fairly large HPC environment which had a large number of NFS attached disks. One of the issues we ran into was unlink() on ext4; it could take quite a long time for large (TB..) files on busy servers. NFS would eventually timeout the request, the client would retry the operation, and get ENOENT back. It turned out that while ext4 blocked until it'd finished every detail of unlink(), the name was immediately removed from the filesystem namespace. NFS is in the category of works well enough, but the edge cases are a mile wide!

m463 6y ago
Wow, that brings back memories. Like "why not mount with intr?" Because NO. (wait, or was it soft mounts?)
- guenthert 6y ago
  Soft mounts may cause silent data corruption (it's actually the applications which don't check the return code on file system operations which cause the corruption, but there are just too many of those). Just don't do it. People sometimes (ignorantly and irresponsibly) recommend (or have recommended -- NFS is squarely in the legacy corner of technology) soft mounts in an attempt to deal with unreliable servers, i.e. prevent clients from 'hanging' if the server doesn't respond. The real solution is of course to fix the darn server / the network.
formerly_proven 6y ago
NFS is a gruesome mess when files aren't exclusively used by a single client (namespace and time(!). A lot of "classic unix" ideas are very, very bad ideas on NFS and will either not work at all (good) or silently sometimes randomly discard data (juck).
- yencabulator 6y ago
  NFSv4(.1) was largely created to fix this. It has delegations, a mechanism for clients to have coherent caches and exclusivity when needed. As far as I know it works just fine, the world just mostly moved away from wanting NFS.

4 ms·

I used to work with a fairly large HPC environment which had a large number of NFS attached disks. One of the issues we ran into was unlink() on ext4; it could

by angrygoat 6y ago

m463 6y ago
Wow, that brings back memories. Like "why not mount with intr?" Because NO. (wait, or was it soft mounts?)
- guenthert 6y ago
  Soft mounts may cause silent data corruption (it's actually the applications which don't check the return code on file system operations which cause the corruption, but there are just too many of those). Just don't do it. People sometimes (ignorantly and irresponsibly) recommend (or have recommended -- NFS is squarely in the legacy corner of technology) soft mounts in an attempt to deal with unreliable servers, i.e. prevent clients from 'hanging' if the server doesn't respond. The real solution is of course to fix the darn server / the network.
formerly_proven 6y ago
NFS is a gruesome mess when files aren't exclusively used by a single client (namespace and time(!). A lot of "classic unix" ideas are very, very bad ideas on NFS and will either not work at all (good) or silently sometimes randomly discard data (juck).
- yencabulator 6y ago
  NFSv4(.1) was largely created to fix this. It has delegations, a mechanism for clients to have coherent caches and exclusivity when needed. As far as I know it works just fine, the world just mostly moved away from wanting NFS.