Hi,
I was playing with Lustre in an environment where there is noticeable
roundtrip latency (10ms) between the client and the servers to figure
out how lustre performs on a WAN link. I tried creating (empty) files
(open/close) and directories from a single client with multiple
processes in parallel - the result looks like this:
# of processes | Files/s | Directories/s
---------------------------------------------
1 | 25 | 50
2 | 50 | 100
3 | 75 | still 100
4 | 100 | still 100
5 | 100 | ...
>5 | still 100 | ...
Can someone shed some light on why there seems to be a hard limit
around 100 op/s? ( 1000ms / 10ms RTT?) Is there only one simultaneous
MDC operation possible? Can this value be tuned? What does
max_rpcs_in_flight exactly do for the MDC in Lustre 1.6? Does file
creation (for empty files) need twice the number of RPCs compared to
directories or is this the close operation?
Thanks a lot,
Christoph
--
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http://www.lrz.de
Abteilung Hochleistungssysteme
Raum I.3.071 - Boltzmannstraße 1, 85748 Garching
Tel. +49 89 35831-8853
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