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NTP in 10.6 with IPv6

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This week, I discovered a bug with NTP in 10.6 that was preventing NTP from syncing on my servers at work. So, their times were all over the place. The worst being about 5 minutes off from another (one was 2 minutes fast, the other was 3 minutes slow). While I don’t use Kerberos, this time difference could have been enough for things to get out of wack.

So, what was the bug? Basically, ntp doesn’t pay attention to whether IPv6 is available or not, and if AAAA records are available for the NTP server you’re using, and IPv6 is disabled, NTP will fail, and never sync. So, let me explain a bit more.

First, get a 10.6 box up and going, on a network that supports IPv6. This might be a bit of a problem for some, but…
Next, disable IPv6 on the 10.6 box.
Now, try something like an ntptrace against an NTP server that has both IPv4 and IPv6 information in DNS.

Watch ntptrace die with:

ntpq: connect: No route to host
ntpq -n -c rv ntp.example.com failed at /usr/sbin/ntptrace line 39.

So now, try an ntptrace against the IPv4 address that ntp.example.com resolves to. Works doesn’t it! Next, try ntptrace against a NTP server that doesn’t have an AAAA record. It also works.

I reported this bug to Apple as 7858336, and within a couple hours, I got back a response saying it was a duplicate of 6736177. So, I’m not the first to find this issue. My hope is that it’s a bug with ntptools only, and not something larger (like the whole dns resolution system). But, I haven’t found anything else that exhibits this problem.

So, for now, I’ve changed my NTP settings to hit against a “hidden” ntp server on campus that doesn’t have an AAAA record. Hopefully this issue will be resolved with 10.6.4, because this certainly is an issue for organizations that are trying to be IPv6 friendly.

As for the question of why I’ve got IPv6 disabled? It traditionally hasn’t gotten along with Xsan. So, it’s off. Simple as that.

Oh, and it seems time.apple.com (the default NTP server for 10.6 (that at least 10.5 before that) systems) doesn’t have any IPv6 info, so it works just fine.

Double “oh”… if you don’t know how to check to see if your time server has an AAAA record, just do this in terminal:

`dig aaaa ntp.example.com` (where ntp.example.com is the server in question).

Good luck, and let’s all hope Apple gets this fixed.

One year of energy data

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Today marks the 1 year anniversary of me collecting electrical usage data. April 1st of 2009, to April 1st of 2010.

Here are some interesting numbers associated with that time period:

  • Highest energy use day (amount): 2009-12-09 (98.02kWH)
  • Highest energy use month (amount): December 2009 (1612.39kWH)
  • Lowest energy use day (amount): 2009-06-18 (9.62kWH)
  • Lowest energy use month (amount): June 2009 (564.88kWH)
  • Mean (average) energy use per day: 29.15kWH (~ $1.35/day)
  • Functional Median energy use per day: 27.55kWH
  • Mode (most common) energy use per day: 18kWH (had to round this)
  • Highest energy use at a given time: 16.11kW (registered on 2009-12-29)
  • Lowest Voltage Recorded: 112.6v
  • Highest Voltage Recorded: 125.3v
  • Average Voltage: 121.4v
  • Number of rows in DB: 525,512

Of interest in all these numbers is first, my lowest use month (Jun) is about 1/3rd the energy used in my highest month (Dec). June in the Willamette Valley is generally pretty mild. Where this December, we had some pretty cold days. Second, I’m only missing 78 minutes worth of data (there are 525,600 minutes in a year, and I have 525,512 records) over the whole year or less than 0.015% of data. Not too shabby.

My voltage is pretty good, at an average of just 1.4v over 120v.

And lastly, I pay an average of $1.35/day for power (at $0.0463/kWH). So, my actual cost per month for power is about $40. Considering I have no gas service, so all my HVAC, hot water, cooking, etc come from electricity, that isn’t bad at all. And given where power largely comes from in this part of the country (Hydro-Electric), my general carbon footprint is actually lower using all electricity than it would be if I was using gas.

Pretty cool. I love the TED, and it’s great having this data. It should be interesting to see numbers a year from now… see how they change, or stay the same from this year.

Mac Mini Server

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Mac Mini ServerIn late January, I was able to upgrade my server to a Mac Mini Server. This is a pretty sweet little box. 2 500GB HDs, 4GB of ram, Intel C2D 2.53ghz. No optical drive, but that’s fine with me, since you can use remote drive, or purchase one of the USB optical drives for the MacBook Air.

Initial setup was quite easy, once I found a copy of “Remote Install” to run on my PowerMac G5. This utility is basically “NetBoot” in an extremely simple interface. It allows the Mini Server to netboot the install DVD. I then changed the HDs to be in a RAID1, and installed 10.6. That took a bit, but other than that, it was quite painless.

bonnie++ reports look like:
/usr/local/sbin/bonnie++ -d / -s 8G -u root:wheel -qfb
server.example.com,8G,,,58807,12,27984,5,,,110101,8,212.3,0,16,12352,59,+++++,+++,
8137,47,543,5,+++++,+++,231,3

Which, isn’t bad at all for dual 5200rpm drives. The machine shipped with two Hitachi HTS545050B9SA02.

Upgrading from the previous server (a Powerbook G4, 1.67ghz, 2GB of RAM, and a single 80GB HD) to this new machine was, to put it simply, breathtaking. The average load on this new machine is consistently less than 0.05, yet on the old PB, it was often upwards of 0.50. So, by that regard, about 10x the performance (realistically, probably more like 6-8x as fast). =) Also, there is a noticeable improvement in performance of the Drobo. I’m pretty sure the FW800 port on the Powerbook is flakey. Added bonus is the 64-bit nature of the new machine… which is really quite nice (really the main time I’ve encountered it is playing with bigint’s in PHP). Also means I can upgrade the ram to 8GB when the prices come down on DDR3 SO-DIMMs.

Add to that the fact that I can now run 10.6, and am not suck with the PPC OS’s, it’s great.

The only thing Apple could have done better? Remove the Mini-DVI port and add a second gig-E port. If they did that, I could probably start using these things at work rather than Xserves. =) Especially if I had an iSCSI SAN.

The machine is very quite. I can only hear the HD’s access occasionally. The fan is near silent. The Mini really is one of the greatest computers Apple has ever designed/made. Other than the dumb single RAM slot the PPC mini’s had, they all have been great machines. I still have a 1st Generation Mac Mini running strong (1.25ghz G4, 1GB RAM, single 80GB HD, 10.5.8 client) at work (it runs Intermapper to monitor various devices around the building. Works great).

Only changes would be the second gig-E port, and it would be sweet if you could buy without the OS (if this was for work, I wouldn’t need even MORE copies of 10.6 (already have spares)). I’d give it a full 10, but I can’t think of anything that’s perfect. =)

[xrr rating=9/10]

If you have any questions, please feel free to leave a comment.

*Image lifted from Apple website.