NFS performance: a question

[Guy Harris]

> In conventional Unix filesystems, bufs for writing file blocks are marked
> B_ASYNC, and nobody is waiting for them to complete; so if the acknowledges
> are slow in coming, that shouldn't inhibit the client from sending some more
> to the server.

It doesn't, at least in Sun's implementation; writes are synchronous on the
server, but not on the client.  The "biod" processes handle asynchronous NFS
writes.  Note that this has the disadvantage that write errors are not
synchronously reported back to the program doing the "write"s; when doing NFS
writes, "out of space" errors are not synchronously reported.  A program should
probably do an "fsync" after writing out a lot of data, and check the return
code from "fsync", so that it can find out about such errors and report them to
the user.