[Lustre-discuss] Does Lustre Support Atomic O_APPEND and Atomic Rename?

[EKC]

Hi,

I have multiple lustre clients setup to do concurrent O_APPEND writes
to the same file. Each O_APPEND is on the order of 1 megabyte. Does
lustre guarantee atomic O_APPEND operations? Also, is there a danger
of deadlocking when I have dozens of clients doing concurrent
O_APPEND's to the same file?

I'd also like to be able to atomically rename this same file. Does
Lustre support an atomic file rename operation? I'm assuming lustre
will FIFO queue my rename and O_APPEND operations on the same file, so
my parent process will have it's O_APPEND or rename operation execue
eventually.

Thanks in advance,

Eser

[Peter J. Braam]

Hi Eser,


Lustre does support concurrent O_APPENDS, and they will be atomic.
There should be no danger of deadlocking. However, I think you will not
find performance is so great - there will be a lot of lock ping-pong and
cache flushes. (If time permits one day we may send O_APPEND directly
to the server in case of concurrency.)

Lustre rename is executed entirely on the server, atomically like for a
local file system.

The operations happen on different servers - the MDS for rename the
OSS's for appends. The file will be open so the rename isn't really
visible to the writers, they keep their file handle during the rename.

- Peter -

-----Original Message-----
Sent: Wednesday, May 31, 2006 1:38 PM
Subject: [Lustre-discuss] Does Lustre Support Atomic O_APPEND
and AtomicRename?
Hi,
I have multiple lustre clients setup to do concurrent
O_APPEND writes to the same file. Each O_APPEND is on the
order of 1 megabyte. Does lustre guarantee atomic O_APPEND
operations? Also, is there a danger of deadlocking when I
have dozens of clients doing concurrent O_APPEND's to the same file?
I'd also like to be able to atomically rename this same file.
Does Lustre support an atomic file rename operation? I'm
assuming lustre will FIFO queue my rename and O_APPEND
operations on the same file, so my parent process will have
it's O_APPEND or rename operation execue eventually.
Thanks in advance,
Eser
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