Keywords: TechAssess uptime
I looked at the archive center high level design and came up with
several questions.
1. Number CPUs for long term non-time critical science. Is this the
design
where we tell the users - "here is your data kid, no dont bother us"
2. DB ingest needs 128 CPUs. I remember seeing a plot by Sergei that
showed the ingest rate ran on a single CPU. I also recall part of
his plot of ingest rate leveling off if some DB function was included.
I don't remember what that option was, but is it one we care about?
3. File servers are shown as 64x8 CPUs. Why do we think we need more
than 10% of the system to be file servers? I'm sure we are disk bound
and not CPU bound.
4. As data flows in from the base camp, we need to consider how to
reliably save the data. Of course we immediately write the data
to disk at the archive site. Where do we put the second (backup)
copy? It seems like we should immediately transmit the data from
the systems at the network interface to the mirror site. For
reliability purposes, I suggest the systems closest to the incoming
network (lets call these buffer systems) each have 2 network
interfaces and the outgoing network connections are different from
the incoming network.
5. How is a database backup done? I presume we cant take the
database offline while we back it up. Do we run a duplicate
database at the mirror site and update both databases simultaneously?
6. Reliability/uptime requirements. I think Jeff and I think about
these
numbers in very different ways. If we want 99.9% uptime, we need
to realize that 'uptime' means that either the entire system is down
or some portion has failed that results in an unnacceptably degraded
operation. What is a complete listing of all uncorrelated failures
that can cause an unacceptable reliability and how can we minimize
these? Let's list just a few obvious failure modes.
1. Network systems connecting archive to outside world.
2. A failure of any one of the 4 IB switches in the AC cluster.
3. Control system software (We will let Jeff estimate this number).
How many non-redundant failure modes of this type do we have? What
are the MTBF and MTTR numbers for each one? We need to think about
what we require from our system components to achieve a 99.9% uptime.
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