Guid Partition or Apple Partition?

starchild108 wrote:

I just bought a 3TB drive and formatted it APM. Disk Utility did not complain.

Launch Disk Utility. Select your 3TB drive. In the lower part of the window, what does it say for "Total Capacity" and "Partition Map Scheme"?

I replaced my parents old bus-powered WD pocket drive (it came Apple formatted) with a self-powered external drive.

I decided to use the old "Apple formatted" to install SL on it for some experiments. Install promptly imformed me that ApplePartition is not a valid partition map to install -- it certainly *seemed* compatible enough for quite a while. So I had to partition with a focus on making it GUID ... good thing there was no critical data on it.

Is that "issue enough" for running only GUID? For me, yes.

I just bought a 3TB drive and formatted it APM. Disk Utility did not complain. What problems might I incur?

No idea, as I never used a disk larger than 1TB with an APM partition scheme.

However, I am very cautious about this kind of stuff ... and extremely protective of my data ... so - if it were me and I absolutely HAD to use the APM partition map, I would partition the drive into 2 partitions ... one of them 2TB the other 1TB.

Is there a reason you can't use GUID instead? Is this a boot drive for a PPC Mac?

fane_j wrote:

Launch Disk Utility. Select your 3TB drive. In the lower part of the window, what does it say for "Total Capacity" and "Partition Map Scheme"?

It says:

Total Capacity : 3 TB (3,000,592,977,920 Bytes)

Partition Map Scheme : Apple Partition Map

Also:

Capacity : 3 TB (3,000,457,555,968 Bytes)

Used : 968.67 GB (968,665,243,648 Bytes)

So, it seems to be able to see the whole drive. And in the finder window it shows the almost 1T I've got on the drive so far and at the bottom of the window it says "2.03 TB available"

I set the drive up APM because I still have a 1GHZ Powerbook that I still use for Protools. So many older plugins that never made the OSX transition or are still too expensive to upgrade. Still works, so I still use it. So, with one drive I can edit in Final Cut on my MBP and export the soundtrack to the same drive, plug it into the PB and Protools away. I don't need the drive to be bootable. The PB has an OS9 partition(Protools) and an OSX partition running 10.3.9. The OSX partition won't recognize the GUID format, I don't think the OS9 partition will either.

So there you have it.

Thank you for the ideas and comments.

starchild108 wrote:

Total Capacity : 3 TB (3,000,592,977,920 Bytes)

Partition Map Scheme : Apple Partition Map

Actually, yes, that's feasible. APM is limited to a max of 32 bits worth of blocks. The highest integer that can be expressed in 32 bits is 4,294,967,295, which means 2TB -- if the block size is 512B. However, the default block size for disks > 1GB is currently 4096B. Divide the figure above by 4096B and one gets 732,566,645 blocks, which is well below the APM limit. So, conceivably, one could have a great deal more than 3TB in APM, and even more by increasing the block size.