Archive for December, 2009

School Christmas Dinner Photo

December 18th, 2009

There’s been a literally a submission for the “best school Christmas dinner” crown:

My Christmas School Dinner, Longhill High School

My Christmas School Dinner, Longhill High School

So here’s the first, and to date only entry. From me! Longhill High School by Innovate Ltd. I can honestly say it’s the best school Christmas dinner I’ve had in recent times.

Turkey roll, stuffing ball,  roast and boiled potatoes, carrots, sprouts and parsnips with gravy. Pudding was Christmas pudding and custard.

Well worth a mention were the parsnips. They were so sweet – absolutely delcious. Apparently they’re cooked in oil and honey which explains it.

If you’ve taken a pic of your Christmas Dinner, send it over along with a short review if you like and I’ll add it on!

Best School Christmas Dinner

December 13th, 2009

At work our canteen is due to be enlarged next year as we can’t seat all the students during a lunchbreak.

So next week we’ve got a Christmas dinner marathon – with the festive meal three days on the trott – and I was wondering how these three dinners will stack up against the school dinners available nationwide.

I therefore call all school staff to forward me a photo of your school chrismas dinner. I’ll stick them up here and we can see who’s getting the best deal!

Converting JVC Hard Disk Camcorder Footage

December 12th, 2009

When will manufacturers learn?

JVC seem to record their footage in MOD format – which is some strange MPG variant. Very few video editors will touch that, hence the need to convert it.

Trusty ffmpeg to the rescue:

ffmpeg -i input.mod -b 9191k -aspect 16:9 -s 720×576 -acodec wmav2 output.wmv

Linux Teacher PC Update

December 11th, 2009

Well we’ve spent a little time on this. Seb’s been helping out and has done the majority of the work so far.

We’ve got the following working:

  • “Domain” logins (against the LDAP database)
  • CCTV Software (via Wine)
  • Themed to look like our standard XP workstations (but not to the extent that you can’t tell the difference. We’re still using the standard Gnome menus). This needs further work.
  • Promethean ActivInspire for Linux (full marks Promethean)

lvm2 Snapshot Write Performance

December 11th, 2009

We’re running an OpenFiler based iSCSI SAN at work and have been very pleased with both its speed and reliability, however I was copying some VM images around the other day and it seemed to me that the disk IO was a little laboured.

A quick Google for lvm2 snapshot performance brought me to an article by Dennis van Dok which prompted me to do a little testing of my own.

Here’s the raw results of the tests Dennis proposes on our system:

Without Snapshot
root@virgil:/mnt/vm# sync; time sh -c “dd if=/dev/zero of=/mnt/vm/test bs=1M count=1000; sync”
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 1.79423 s, 584 MB/s

real    0m9.697s
user    0m0.000s
sys     0m2.530s

With Snapshot
root@virgil:/mnt/vm# rm test
root@virgil:/mnt/vm# sync; time sh -c “dd if=/dev/zero of=/mnt/vm/test bs=1M count=1000; sync”
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 1.67537 s, 626 MB/s

real    0m49.165s
user    0m0.000s
sys     0m2.020s
root@virgil:/mnt/vm#

Now I didn’t carry that out in optimal test conditions. The filesystem is mounted over iSCSI and there’s caching and multipathing in the mix too so this is far from scientific. It’s quite possible that some real traffic from one of the VMs has skewed the result somewhat, but none the less that’s a 5x slow down on write with a snapshot compared to without.

So it’s a tricky dilema. Snapshots are so convenient yet appear to impose such a penalty. We’re going away to rethink how we “do” snapshots.