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The Dice Project


(Inf logo) Operational Meeting Infrastructure Unit Report
25th February 2019

  1. Appleton Tower datacentre work

    Paul Hutton writes: "[...]

    "Week commencing 18 March:
    Contractors from Uninterruptible Power Supplies Ltd (UPS Ltd) will be installing racking and batteries in room 3, along with switching the UPS over to the new batteries.

    "That second piece of work will result in a loss of UPS cover for one working day. There should be some flexibility in scheduling that work, so if there are dates in that week which will cause a problem for you, please let me know.

    "I appreciate that this work will cause some inconvenience and can only apologise. Moving the batteries from the man room into room 3 will allow us to keep them within their operating temperature range and should result in greater reliability and longer battery life."

    If this date doesn't suit anyone, please let us know ASAP.

  2. SLAAC for server wires

    The Appleton Tower server wire had forward SLAAC-style addresses enabled on Tuesday 19th. This brings us to 1239 AAAA entries in inf.ed.ac.uk.

    We'll give it a couple of weeks to shake down before doing the last remaining two (S32 and S33 in the Forum). How would Tuesday 12th March sound for that? There are 367 IPv4 addresses on those two wires combined.

    (In case anyone was wondering, it's just a case of changing %slaacReverseFile to %slaacFile in dns/inf6 to enable generation of the forward entries.)

  3. RFC4941 addresses

    Graham asked in the chatroom about RFC4941 (privacy) addresses. For Linux these can be enabled by setting the use_tempaddr interface variable (see networking/ip-sysctl.txt in the kernel documentation).

    We hadn't expected to want to enable this:

    Comments to the contrary (and project proposals!) are invited...

  4. Wire headers

    Our list of subnets and their uses is here.

  5. SMSR power bars

    Some of the B.Z14 power bars have been replaced, with the remainder scheduled to be done soon. This gives us a few benefits:

    1. We will be able to turn machines off and on remotely. (The users won't though. If that's thought to be necessary, a development project will be required to enhance our tools.)
    2. We will have a random delayed turn-on of outlets after any power outage, which will smooth the load being returned to the UPS.
    3. We will also turn on the switches a couple of seconds or so after power is restored, which will allow time for UPS power to stabilise.
  6. Aggregate network traffic

    Because we needed something like it for the EdLAN musings, there are now additional sets of graphs (Forum, AT) which show (most of) the aggregate traffic flowing into and out of the core switches. Intra-core is excluded. The y axis is in octets/second, so multiply by around 8 to 10 to convert to bits/second (the actual value depends on the encoding being used on the links).

    The configuration which has been set up to drive this includes the rrd files from both the old and new core switches. Interestingly the aggregate Forum traffic increases as the old switches were replaced.

    (While trawling MIBwalks, it looks as though the new core switches do at last provide some counters for the virtual VLAN interfaces, so we'll set things up to instrument and graph those at some point. Could be interesting...)


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