Quick question about joining HDs...

BlindingLights · Aug 12, 2006

Okay, here's what I want to do:

I have my Intel iMac 17" with a 160 GB internal HD. I also have a Maxtor 100 GB external USB drive. Is there any way to join them so that I get 260 GB of free space in my Macintosh HD? I've heard of RAID (other than that it stands for Redundant Array of Inexpensive Disks, that's all I know from Wikipedia), and not sure what the heck it is or if it has anything to do with this, but I was thinking about RAID.

alucard · Aug 12, 2006

RAID is used mainly for fault tolerance. It's true that when you make a RAID (their are several, RAID 0, 1, and 5 being the most popular) depending on the one you choose expands the capacity but it also uses space as well. For example for a RAID 5, which is the most fault tolerant) you need at least 3 HDD. If they were all 500GB HDD's you would have a total of 1.5TB. However you lose one whole drive for fault tolerance in case one dies giving you only 1TB of info.

BlindingLights · Aug 12, 2006

Okay, that's cool... but my question is could I use RAID to join together my iMac's internal 160GB HD and an external USB 100 GB HD so I have 260 GB available in my Macintosh HD (open finder and look on the bottom)... I more or less want to mold them into a single drive, similar to how a Mac Pro can have up to four drives of 500 GB.

PowerBookG4 · Aug 12, 2006

I don't believe there is a way to do this with an internal drive and an external drive.

asolo · Aug 12, 2006

BlindingLights said:
Okay, that's cool... but my question is could I use RAID to join together my iMac's internal 160GB HD and an external USB 100 GB HD so I have 260 GB available in my Macintosh HD (open finder and look on the bottom)... I more or less want to mold them into a single drive, similar to how a Mac Pro can have up to four drives of 500 GB.

My understanding with PC is that any/all RAID configurations are dependent upon the mother-board being set up to accomodate them. Can't just RAID a couple of drives into a machine without that support. Have little doubt Apple's situation is the same but willing to be enlightened.

PowerBookG4 · Aug 12, 2006

asolo said:
My understanding with PC is that any/all RAID configurations are dependent upon the mother-board being set up to accomodate them. Can't just RAID a couple of drives into a machine without that support. Have little doubt Apple's situation is the same but willing to be enlightened.

It does not need to be the motherboard per sey, but it does have to be a board. You can buy a RAID card that goes in the pci express slot in the newer powremac quads, or the new mac pros.

Avalon · Aug 13, 2006

With Disk Utility you can create a RAID, and as far as I know you can even do that with external drives.

But actually, in your case that's not a good idea...

If you want to combine 2 disks to have one big volume, you need RAID level 0. But that means that, if you remove the external drive, you can't use your computer, nor can you use the external drive elsewhere. This is because the data (in this case it includes the system) is spread over the 2 disks, and one cannot work without the other.
Building a RAID with 2 differently sized drives means you will loose space, as it will take the smallest size and use it for all disks. In your case, that means instead of getting 260GB, you'll get only 200GB, the rest being unusable.
And also, you would need an additional drive to backup your data, because in a RAID 0 setup, if one drive dies, there's no way to get back any data from the rest of the drives.

So mainly, I would suggest you keep it the way it is.

BlindingLights · Aug 13, 2006

Avalon said:
With Disk Utility you can create a RAID, and as far as I know you can even do that with external drives.

But actually, in your case that's not a good idea...

If you want to combine 2 disks to have one big volume, you need RAID level 0. But that means that, if you remove the external drive, you can't use your computer, nor can you use the external drive elsewhere. This is because the data (in this case it includes the system) is spread over the 2 disks, and one cannot work without the other.
Building a RAID with 2 differently sized drives means you will loose space, as it will take the smallest size and use it for all disks. In your case, that means instead of getting 260GB, you'll get only 200GB, the rest being unusable.
And also, you would need an additional drive to backup your data, because in a RAID 0 setup, if one drive dies, there's no way to get back any data from the rest of the drives.

So mainly, I would suggest you keep it the way it is.

Okay, you answered my question VERY thoroughly Avalon! Rep points for you. Thank you so much.

alucard · Aug 13, 2006

Avalon said:
With Disk Utility you can create a RAID, and as far as I know you can even do that with external drives.

But actually, in your case that's not a good idea...

If you want to combine 2 disks to have one big volume, you need RAID level 0. But that means that, if you remove the external drive, you can't use your computer, nor can you use the external drive elsewhere. This is because the data (in this case it includes the system) is spread over the 2 disks, and one cannot work without the other.
Building a RAID with 2 differently sized drives means you will loose space, as it will take the smallest size and use it for all disks. In your case, that means instead of getting 260GB, you'll get only 200GB, the rest being unusable.
And also, you would need an additional drive to backup your data, because in a RAID 0 setup, if one drive dies, there's no way to get back any data from the rest of the drives.

So mainly, I would suggest you keep it the way it is.

Exactly. I couldn't have said it better myself