today’s amuse-cerveau – January 31, 2010

Things which amused or interested me today:

today’s amuse-cerveau – January 26, 2010

Things which amused or interested me today:

The REAL cage nut tool

Anyone who’s spent time installing servers or other electronics in standard 19″ (or 24″) racks has run into this problem. In these racks, the holes are square, and most equipment has brackets that require screws to attach. So you install a cage nut, which is a square-shaped nut surrounded by a razor-sharp piece of metal that’s designed to both hold the nut in the equipment rack and to cut the fingers of anyone who tries to insert the nut manually:

Cage nut in rack rail

So most rack and equipment manufacturers take a measured amount of pity on the poor installers, and included a bent piece of metal (seen in the illustration above) that they call a “cage nut insertion tool”, which is a) cheap and b) still a pain to use. Oh and did I mention it’s cheap? And they don’t work well at all for when you need to remove the nut later on.

A long time ago, I discovered a gentleman in Australia (whose web site I now can’t find) making these beautifully simple tools to insert and remove cage nuts. It’s a small machined piece of aluminum with a lever that’s shaped to carefully clamp and squeeze the cage nut, so that the razor sharp edges of the nut will pass through the square opening. Once the cage nut is seated, release the tool, and the razor sharp edges hold the nut in place.

Cage nut tool holding cage nut

Removal is equally as good. Instead of the traditional method — insert a screwdriver on one side of the nut so that the nut springs out and shoots across the room — simply apply the tool, squeeze, and remove.

It’s a simple, brilliant piece of technology, and anyone who’s got more than one equipment rack to deal with should have one in their tool chest. You’ll throw out every bent piece of metal that comes with cage nut kits as soon as you find them.

Available from Cables Plus USA or Rackmount Solutions. Disclaimer: I haven’t dealt with either of these businesses, so do your due diligence first. Disclaimer II: Not getting paid or anything, I just really like this tool.

5400RPM vs 7200RPM hard disks — should you care?

A recent twitter discussion via Doctor Karl led me to the question of whether it matters that while large capacity desktop drives spin anywhere between 7200RPM and 15,000RPM, most large capacity laptop drives spin at only 5400RPM.

For years, 5400RPM was the standard speed of a hard drive, back when 1GB and 2GB were huge. The speed demon server drives that came out shortly thereafter were 4GB and 9GB 7200RPM drives, and required active cooling so they didn’t melt from the heat. Everyone understood that 7200 RPM was faster, because it delivered your bits quicker.

Fast forward ten years, and you can get 1TB and 2TB hard drives spinning at 7200RPM, and smaller laptop drives at 500GB and 1TB spinning at 5400RPM. (You can also get 600GB drives spinning at 15,000 RPM, but that’s today’s bacon-cooker for servers.)

But is the 5400RPM laptop drive really slow?

I would argue it’s not. Areal Density increases as drive capacity goes up; and today’s 3.5 inch and 2.5 inch drives aren’t physically bigger than the same size drives of the past, meaning their areal density has gone way up (see some examples on Wikipedia’s Memory Storage Density page).

This means that when a 1TB disk makes one revolution (in 1/5400th of a second), it’s picking up much more data from the platter than, say, an 80GB disk spinning at 7200RPM is after a single revolution in 1/7200th of a second.

Granted, you’ll still get faster performance out of a 7200RPM drive than a same-sized 5400RPM drive, but it’s not the end of the world to pick the slower-rotating disk. It also won’t get as hot as the faster one.

Now keep in mind, too, that these speeds are talking about sequential or mostly-sequential data access, when you start at one point on the disk, and read continuously to a later point, like playing a record or a CD. Unless you’re playing audio or video, most data access isn’t like this. And that kind of performance — operations per second — hasn’t increased much over 20 years. But that’s another post.

today’s amuse-cerveau – January 25, 2010

Things which amused or interested me today: