Build Your Own SATA Hard Drive Switch

Mikey Win writes "ExtremeTech shows us a cool hardware hack that allows multiple operating system to boot without dealing with any tedious BIOS setup changes. How? By building your own SATA hard drive switch. The result? You can expect a longer hard drive life span, power supply load reduction, and partitions protected from becoming overwritten or corrupted."

Comments

Dubious claims

[MrEricSir]

"You can expect a longer hard drive life span"

Well, assuming you build it right.

Mad scientist hard drive switch

[Captain Spam]

Hrmph. Call me when the switch in question is tied to a massive, mad scientist-quality switch, clearly labeled in big letters with "LINUX" on one side, "WINDOWS" on the other. It should also make a satisfying mechanical switching noise whenever I pull it. And if you can make lightning crack outside my window every time, that'd be nice, too.

Re:Mad scientist hard drive switch

[Midnight Thunder]

Hrmph. Call me when the switch in question is tied to a massive, mad scientist-quality switch, clearly labeled in big letters with "LINUX" on one side, "WINDOWS" on the other. It should also make a satisfying mechanical switching noise whenever I pull it. And if you can make lightning crack outside my window every time, that'd be nice, too.

I'll get Igor to start work on that right away.

Re:Mad scientist hard drive switch

[The Yuckinator]

I think you mean iGor, the Mad Scientist's assistant for the 21st Century.

I like it

[John Napkintosh]

Low tech and simple. The only thing I might do differently is attach the rotary knob to an unused PCI backplane thingy instead of an unused drive bay - would make it harder for inquisitive people/pets to crash things.

Re:I like it

[harrkev]

After giving the article a quick skim, it also looks like they switched the ground wires too, which is unnecessary. All you really need to do is to switch the red and yellow wires (+12V a,d +5V). They can all share ground no problem.

Re:I like it

[gweihir]

In fact switching the ground wires under power gives you a high risk of blowing up your drives: If you use a non-bridging switch (or it does not make perfect contact, as cheper ones may do after some time), you can have a situation where +5V and +12V have contact, but ground does not. This typically leads to immediate death of the whole drive electronics.

These people have no clue what they are doing.

Re:I like it

[Culture20]

SATA drive "caddie" manufacturers went cheap when they found out that SATA data and power plug-n-chug easily. Most are just a simple tray to hold-in/lever-out a drive. Even a lot of reasonably old SCSI caddies are this way (but the connectors are much more solid). They're nothing like the IDE/ATA caddies of yore.

Re:I like it

[gweihir]

In general, switching this thing while the computer is running would, at least, cause massive problems for any OS that happened to be running. So this is something to be avoided in any case.

Not necessarily. If you unmount (safely remove for Windows) the running drive before swithcing it off, it is fine and just corresponds to a hot-unplug followed by a hot-plug. Doing it for a mounted drive (as, for example, the system drive) is indeed a very bad idea. For a data drive, it can make sense.

How is this a SATA switch?

[james_shoemaker]

It's just a drive power switch. I was expecting the actual SATA connection to be switched not just the power to the various drives.

Re:How is this a SATA switch?

[gabebear]

I was excited about building an active SATA multiplexer... but this is just dumb. I did something similar a long time ago with IDE drives; instead of powering one drive down I had the switch attached to jumper positions so that the switch controlled master/slave.

Sata Hub (but not a switch)-> http://www.cooldrives.com/sahub5muussi.html

Re:How is this a SATA switch?

[Fourier]

Well, if you include a few more pins, then you should be able to merely extend the current design to include the data cables...

Only if you want to deal with a bunch of CRC failures. You can't really expect to be able to mess around with signal lines when you're switching at 1.5 or 3.0 Gbps.

Re:How is this a SATA switch?

[Fourier]

I've helped to guide a bunch of SATA boards from prototype to product. From personal experience, I can tell you that a switch put together "half-decently" is very likely to result in unreliable SATA communication.

Grub

[jgtg32a]

Do people really think that Grub is that hard or this just another case of because we can.

This is hardly extreme.

[rmadmin]

This is a power switch. Nothing more. Certainly not a sata switch. As much as I love soldering.. I'll stick with grub for this one. Then I can at least share my media across OSes.

Sounds like a recipe for disaster

[mr_da3m0n]

I would like to see what terrible, terrible things happen when some idiot let loose near your computer decides that the knob on it looks weird and takes it for a spin. In the middle of a kernel compile.

And by terrible things, I mean manslaughter.

Re:Sounds like a recipe for disaster

[pathological liar]

Hans, is that you?

Higly dangerous design

[gweihir]

The design switches ground (Black) as well, instead of keeping it permanently connected. This means that if you use a non-bridging rotary switch (i.e. it does not short out neigbouring connectors when turning it, but has a short phase where all wires are insulated), you could kill disks when switching under power. This happens when +12V and +5V already (or still) have contact but ground does not. The effect is that -7V (a negative voltage) gets applied from Red to Yellow. Typical electronics have a tolerance of -0.5V on their supply lines and die very fast (miliseconds) if that is exceeded in negative direction.

The same can happen if your (bridging) switch gets a bit corroded and does not make perfect contact anymore. This is not so uncommon.

My bottom line is that these people have no clue what they are doing and you should under no circumstances copy this faulty design. If at all, then switch only Red and Yellow, but leave Black
allways connected at all devices. Not only is that safe, there is in fact no sane reason at all to switch Black. I can only conclude that the idea of the designers was to simply switch all wires, without any understanding of the consequences.

I think this solution is also overdone. I have XP and several Linuxes on a GRUB multi-boot on two computers. True, once or twice per year I need to use a KNOPPIX CD or memory stick to boot my system and reinstall the boot manager. Takes about 5 minutes each time. Not an issue at all.

Re:Signal But no Power == BAD?

[gweihir]

Having a signal connected to the hard drive, and no power applied, at least in a traditional TTL or CMOS circuit, is not a good idea.

Since SATA is based on LVDS, this might not suffer from the typical CMOS or TTL problems, but I would investigate it a bit further.

SATA has coupling capacitors, so this is not a problem.

these types of articles are good

[RGRistroph]

Most of the comments here are negative. The criticisms about swappable drive bays being better and that ground should not be switched are all valid.

However, I think articles like this are good. More people should actually do stuff, even if they burn out a few harddrives or power supplies in the process.