Re: NFSv4/pNFS possible POSIX I/O API standards

["Latchesar Ionkov" <lucho@ionkov.net>]

Hi,

One general remark: I don't think it is feasible to add new system
calls every time somebody has a problem. Usually there are (may be not
that good) solutions that don't require big changes and work well
enough. "Let's change the interface and make the life of many
filesystem developers miserable, because they have to worry about
3-4-5 more operations" is not the easiest solution in the long run.

On 12/1/06, Rob Ross <rross@mcs.anl.gov> wrote:
> Hi all,
>
> The use model for openg() and openfh() (renamed sutoc()) is n processes
> spread across a large cluster simultaneously opening a file. The
> challenge is to avoid to the greatest extent possible incurring O(n) FS
> interactions. To do that we need to allow actions of one process to be
> reused by other processes on other OS instances.
>
> The openg() call allows one process to perform name resolution, which is
> often the most expensive part of this use model. Because permission

If the name resolution is the most expensive part, why not implement
just the name lookup part and call it "lookup" instead of "openg". Or
even better, make NFS to resolve multiple names with a single request.
If the NFS server caches the last few name lookups, the responses from
the other nodes will be fast, and you will get your file descriptor
with two instead of the proposed one request. The performance could be
just good enough without introducing any new functions and file
handles.

Thanks,
    Lucho