Boot a Mac from an external drive, spinning up only that drive?

December 20, 2011 8:15 PM

Boot a MacBook Pro from an external drive *without spinning up the MBP's internal drive*?

August 2006 MacBook Pro, running 10.5, has an almost-dead drive. (Drive starts very loud grinding noise/vibrations after, generally, a few minutes of operation.)

Any way to boot this machine from an external drive *either* without ever spinning up its own internal drive *or* with the option to manually spin down the internal drive soon after booting?

No concern re. data loss on the MBP's drive; I already have a new machine and I'm just trying to determine whether the old machine can be made at all usable without actually replacing its drive.

(MBP is known-happy booting and running from an external drive; the issue is just the extreme noise and vibration that start coming from its internal drive while it runs this way.)

posted by kalapierson to computers & internet (11 answers total)

The best option is to simply pull the hard drive and put it into an enclosure, if you still need it. If you're already opening it up, you may as well just replace it with another HDD or SSD. Take a look at iFixit for step-by-step instructions for disassembly and reassembly. It's actually quite easy to do.
posted by Blazecock Pileon at 8:24 PM on December 20, 2011

I'm asking whether there's a solution that does not require opening it up.
posted by kalapierson at 8:33 PM on December 20, 2011

You can boot from a CD or a FireWire (maybe USB?) drive, hold down the Option key as you restart the computer and then you can choose the startup device.
posted by zomg at 8:49 PM on December 20, 2011

Not sure if this gets at what you want, but you should be able to either unmount the internal disk or put it to sleep if you aren't booting from it. Have you tried these and do they address the sound/vibration issue? Also make the drive private with respect to spotlight..
posted by drpynchon at 9:06 PM on December 20, 2011

What I'm asking is whether there's an undocumented hw or startup-key-combo solution that *doesn't also spin up the internal drive.*

I try pretty hard not to ask easily googleable questions on AskMe. If this one seems to have an obvious solution, my question's not clear enough (or people aren't reading my question).
posted by kalapierson at 9:07 PM on December 20, 2011

Thanks drpynchon, my post overlapped yours.
posted by kalapierson at 9:08 PM on December 20, 2011

Also have a look at this. I think it might get at your solution.
posted by drpynchon at 9:17 PM on December 20, 2011

I don't think you can avoid spinning it up initially— most drives are set to spin themselves up as soon as they get power (or receive the first communication from the host). This can be changed, usually by messing with jumpers but possibly through software; but it sounds like it would be much easier for you to boot fully into OSX and then unmount/spin down the disk.
posted by hattifattener at 9:37 PM on December 20, 2011

Maybe you could fool around with Open Firmware commands, and see if you can permanently wipe the hard drive from your device list.
posted by Blazecock Pileon at 10:17 PM on December 20, 2011

The only way to get the drive to never spin up at all is for it to not be plugged in. As soon as the computer is powered up enough to be executing code (in S0, as they say) the hard drive has power and will spin up. It doesn't even matter if the host controller never talks to it. Power on the power pins and it will spin up. Most 2.5" drives do not have spin up/down setting jumpers, so it would have to be explicitly told, after the fact, to spin back down.

If you're OK with it spinning up during boot but then spinning it down afterward, you can force unmount the disk in Disk Utility and it should spin down after that. You could even use the above suggestion to set it to never mount. Additionally, you can also set the system to always spin it down after a minute of no activity like so:

pmset -a disksleep 1
(in 10.4 or earlier replace 'disksleep' with 'spindown')

Even set up like that, it may spin back up after a wake from sleep. That setting is global, by the way, so the external boot drive would also spin down (and have to spin back up) very frequently.

Your best bet really is to replace the drive.
posted by bigtex at 10:47 PM on December 20, 2011 [1 favorite]

I don't know of any way to stop a notebook drive from spinning up when it receives power. I don't think it is possible, the controller card has to read some data off the platters to be able to report itself to the controller.

I don't know the Mac bios, but it is possible that if you disable the IDE controller, it *might* not spin. But what that would do is allow the drive to spin right back down if it has internal spin-down circuitry. You might have to check/set it via something like hdparm.

SCSI drives have that capability, but it is invoked by a jumper and/or a control line on the connector. But even then, it has to spin up before it will be ID'd by the host adapter.
posted by gjc at 6:19 AM on December 21, 2011