Craig Tierney wrote:
Joe Landman wrote:
Craig Tierney wrote:
Chris Samuel wrote:
----- "I Kozin (Igor)" <[EMAIL PROTECTED]> wrote:
Generally speaking, MPI programs will not be fetching/writing data
from/to storage at the same time they are doing MPI calls so there
tends to not be very much contention to worry about at the node
level.
I tend to agree with this.
But that assumes you're not sharing a node with other
jobs that may well be doing I/O.
cheers,
Chris
I am wondering, who shares nodes in cluster systems with
MPI codes? We never have shared nodes for codes that need
The vast majority of our customers/users do. Limited resources, they
have to balance performance against cost and opportunity cost.
Sadly not every user has an infinite budget to invest in contention
free hardware (nodes, fabrics, or disks). So they have to maximize
the utilization of what they have, while (hopefully) not trashing the
efficiency too badly.
multiple cores since be built our first SMP cluster
in 2001. The contention for shared resources (like memory
bandwidth and disk IO) would lead to unpredictable code performance.
Yes it does. As does OS jitter and other issues.
Also, a poorly behaved program can cause the other codes on
that node to crash (which we don't want).
Yes this happens as well, but some users simply have no choice.
Even at TACC (62000+ cores) with 16 cores per node, nodes
are dedicated to jobs.
I think every user would love to run on a TACC like system. I think
most users have a budget for something less than 1/100th the size.
Its easy to forget how much resource (un)availability constrains
actions when you have very large resources to work with.
TACC probably wasn't a good example for the "rest of us". It hasn't been
difficult to dedicate nodes to jobs when the number of cores was 2 or 4.
We now have some 8 core nodes, and we are wondering if the policy of
not sharing nodes is going to continue, or at least modified to minimize
waste.
Last time I asked (recently...) TACC intends to continue scheduling
per-node, even with 16 cores/node.
Sorry to be late with this but the hurricane season is getting
interesting and e-mail's taken a bit of a hit.
--
Gerry Creager -- [EMAIL PROTECTED]
Texas Mesonet -- AATLT, Texas A&M University
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843
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