how many GB can you have as a boot drive on Macbook Pro os x lion

I'm not sure what your question actually is, but here goes. There is no limit as to the size of a boot volume except the limit of available hard drives.

Check the specs for your Mac model to determine if it supports 6 Gb/s. Same goes for the hard drives.

Your idea of backing up your boot volume via Time Machine to another partition on the same disk is foolhardy. If the drive fails, as all drives do sooner or later, everything will be gone including the backup. You might as well not back up at all as leave yourself vulnerable to that disaster. Always use a separate disk for backup. If you do, you will also sidestep the knotty problem of creating a boot camp partition on a multi-partitioned drive, which Boot Camp Assistant really doesn't want to do.

If you think you need 1.5TB for OSX, you should have a 3TB drive for Time Machine. But I suspect you don't really need 1.5 TB for either OSX or Windows, and could make do just fine with a pair of 1TB or 2TB drives, one internal and the other external for a TM backup of OSX. I don't see any merit in the idea of connecting a bare 3.5" drive externally to the hard drive bay in a MBP.

Having 1TB of free space available isn't going to make Windoze any faster than having 500 GB available. Either is far more than enough. And the hassles you're likely to encounter using an externally-powered drive for your OS while connecting it to a SATA cable that's designed to power a drive make the whole project enough of a gamble to be just silly.

Hi

This really becomes down to an old saying: "You can have a good system or a cheap system". Not both at the same time.

As eww already stated you probably do not need 1,5GB for OS X or even WIN7 system. And the speed of an operating system comes down not when the partition has nearly filled, but it is rather related to the physical drive utilization. But OS X and WIN7 are both quite good handeling the hardware even when it's not that top-noch.

If you are into storage, buy a separate external storage device (for about $250 per 2TB) and attach it via FireWire - http://store.westerndigital.com/store/wdus/en_US/DisplayProductDetailsPage/produ ctID.106590800

And have a 1TB harddrive for operating systems giving both the MAC and WIN about 500GB of diskspace. That would set you back for about $100 or less.

So for a total of 3TB of storage you would then have been spent around $350 and you have a system that can deliver both speed and reliability.

Keep in mind that when you have the timemachine backup on the same physical drive as the stuff you are backing up, it does not only make the backup unnessecary but it will also make the usage of the computer very slow during the backup since the backup proccess reads and writes to the same physical drive.

I understand your technical curiosity and its not in anyway wrong to poke around (as I have done so as-well) but just understand that when you create this hazard platform combining original and "backup" data on the same drive you should really consider what information you store on that system. Just something to think about.

"...and yea i'm going to buy a 1 tb external storage..."

If that's the one you plan to use for TM, it should have twice the capacity of your OSX boot volume.

That is true that you cannot use an external drive for bootcamp partition but you can use that external drive as an external drive in windows also. So this does not limit your storage usage.