Hi all, we have a testbed running with Lustre 1.8.3 and a RTT of ~4ms (10GE network cards everywhere) for a ping between client and servers. If I have read the iozone source code correctly, iozone reports bandwidth in KB/s and includes the time for the open() call, but not for close(). If I write a single 64 byte file (with one I/O request), iozone tells me something like '295548', which means ~295 MB/s. Dividing the file size by the bandwidth, I get the time that was needed to create the file and write the 64 bytes (with a single request). In this case, the time is about 0,2 micro seconds which is way below the RTT.
That mean for a Lustre file system, if I create a file and write 64 bytes, the client sends two(?) RPCs to the server and does not wait for the completion. Is this correct? But it will wait for the completion of both RPCs when the file ist closed? The numbers look different when I disable the client side cache by setting max_dirty_mb to 0. Regards, Michael -- Michael Kluge, M.Sc. Technische Universität Dresden Center for Information Services and High Performance Computing (ZIH) D-01062 Dresden Germany Contact: Willersbau, Room A 208 Phone: (+49) 351 463-34217 Fax: (+49) 351 463-37773 e-mail: michael.kl...@tu-dresden.de WWW: http://www.tu-dresden.de/zih
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