November 28th, 2013

Tall ships (porthole)

(no subject)

It occurs to me that I never did post the answers to last year's Name That Song. Well, it'd be a bit mean to do another quiz before posting the answers to the first, and it'd also be a bit mean to just post the answers now when you've all forgotten about it. So consider this advance warning that I'll be posting the answers in a day or two.

It's also very tempting to pad out the remaining three days of NaBloPoMo with this, the answers, and another quiz... but there's so many other things to post. You can find out in 5 and a half hours what I've decided to do!
Sysadmin

(no subject)

Since I'm sure talismancer will post even more snark if I just leave it at the two previous posts for today, have a not-even-slightly-epic snippet of computer fail.

There's an unexpected downside to reducing the amount of servers you need by consolidating several under-used ones into a bunch of virtual machines on one real server: when (not if) the server fails you lose all the virtual machines.

In this case it was a disk failure that took out the server. Now, disk failures had been planned for by creating a RAID-5 array, which uses MATHS to ensure that you can lose a disk in the array without losing any data.

So Murphy ensured that on the server in question two disks failed a few hours apart, at which point the RAID controller threw its hands up in the air and gave up. IT then had to spend several hours rebuilding the various VMs from backups.

I wonder how common double disk failures actually are? I do recall reading something about this a few years ago - someone had a look at the specified uncorrectable error rate (how likely the drive is to be unable to read a sector). They worked out that with high-capacity hard disks (on the order of 1TB) there's a scarily high chance of a RAID-5 rebuild failing due to an uncorrectable error on one of the remaining disks.