PowerMac Says Goodbye

[Chris Hocking]

Actually, thinking about it, from memory, optical drives use parallel ATA connections whereas hard drive uses serial ATA busses. Opps!

I guess I was just talking rubbish...

[Jeff Kilgroe]

Originally Posted by Chris Hocking

Actually, thinking about it, from memory, optical drives use parallel ATA connections whereas hard drive uses serial ATA busses. Opps!

I guess I was just talking rubbish...

Actually you're not...

The Mac Pro appears to have 4 SATA2 (3Gbps) connectors for the 4 intended HDD locations. It also appears to have two additional SATA2 connectors up front for the optical bays as well as two ATA/100 connectors. This gives them the freedom of using EIDE/ATA or SATA interface optical drives or whatever else is mounted in the two front bays. I don't think the answer will be known for sure until someone gets their hands on a Mac pro to try some of this out. But unless there are specific restrictions within the system BIOS/ROM that prevent alternate uses for the frontal ATA and/or SATA connectors, there's no reason these couldn't be used for hard drives or other devices as well. Should be entirely possible to leave the optical drive in one bay and the system drive in another (just use a 5.25" drive bracket to fit the 3.5" HDD in that space), thus leaving all 4 primary HDD locations open for use as a RAID volume.

If anyone wants to contribute donations so I can buy a new Mac Pro, I'd be happy test all this out and post a detailed review. ;-)

[Jeff Sayre]

Originally Posted by Barry Gribble

So if you put 3 500 GB drives together in a RAID, what is the totaly amount of disk space you will have available? Isn't there some redundancy that eats space?

I was going to post a detailed description of the various common RAID levels (0,1,5) but found that Wikipedia has a good article on RAID configurations and does a better job than I would have anyway.

http://en.wikipedia.org/wiki/Redunda...ependent_disks

A couple of points to note about RAID 0 arrays:

- With RAID 0 there is no data redundancy which means your data is not safe from disk failure. If one disk goes then the data on the other disk(s) is usually lost as well.

- With RAID 0, the total array space is determined by the smallest drive. So, a 250 GB drive and a 500 GB drive will not create a 750 GB array. Instead, it creates a 500 GB array (250 + 250). Therefore, if setting up a RAiD 0 array, always use disks of the same size.

[Jeff Kilgroe]

Originally Posted by Jeff Sayre

A couple of points to note about RAID 0 arrays:

- With RAID 0 there is no data redundancy which means your data is not safe from disk failure. If one disk goes then the data on the other disk(s) is usually lost as well.

Yep. However, regardless of which sort of disk configuration is used, it's always wise to have a good backup strategy in place. I've lost RAID-5 arrays when a PSU goes bad and fries 3 of the 5 connected HDDs. Poof - gone.

- With RAID 0, the total array space is determined by the smallest drive. So, a 250 GB drive and a 500 GB drive will not create a 750 GB array. Instead, it creates a 500 GB array (250 + 250). Therefore, if setting up a RAiD 0 array, always use disks of the same size.

Not necessarily true. Some newer RAID controllers (even the Adaptec and Mylex SCSI RAID controllers from 10 years ago) would allow mismatched capacities to be used in a striped volume. I haven't tried it with OSX, but within Windows NT, 2K and XP, the software RAID allows for specifying different block and stripe sizes for each drive and it's entirely possible to combine a 500GB and a 250GB to form a 750GB stripe set (RAID 0) configuration. While I've never done it with a 250 and a 500, I have built systems with mismatches such as 20GB + 30GB to get a 50GB volume.

Now, just because it's possible, I would not recommend it. To provide the best performance and reliability, it would be best to use drives of equal capacity within the RAID configuration. I manage tons of systems and have my full share of failures every year. I've become anal enough that I won't even RAID drives together in any form of stripe set (RAID 0, 3, 5, 7) unless the drives are the same make and model and preferably from the same production series.

[Jeff Sayre]

Originally Posted by Jeff Kilgroe

Yep. However, regardless of which sort of disk configuration is used, it's always wise to have a good backup strategy in place. I've lost RAID-5 arrays when a PSU goes bad and fries 3 of the 5 connected HDDs. Poof - gone.

Boy, isn't that true. RAID 5 or any other RAID with redundancy should not be considered a backup strategy. Any "backup strategy" that includes actively using your data--or the possibility of doing so--is not a backup strategy.

Originally Posted by Jeff Kilgroe

Not necessarily true. Some newer RAID controllers (even the Adaptec and Mylex SCSI RAID controllers from 10 years ago) would allow mismatched capacities to be used in a striped volume. I haven't tried it with OSX, but within Windows NT, 2K and XP, the software RAID allows for specifying different block and stripe sizes for each drive and it's entirely possible to combine a 500GB and a 250GB to form a 750GB stripe set (RAID 0) configuration. While I've never done it with a 250 and a 500, I have built systems with mismatches such as 20GB + 30GB to get a 50GB volume.

Now, just because it's possible, I would not recommend it. To provide the best performance and reliability, it would be best to use drives of equal capacity within the RAID configuration. I manage tons of systems and have my full share of failures every year. I've become anal enough that I won't even RAID drives together in any form of stripe set (RAID 0, 3, 5, 7) unless the drives are the same make and model and preferably from the same production series.

This is good information, Jeff. I guess I know it is possible in certain circumstances to create mismatched capacity RAID 0 arrays but I never thought it a good idea. Your suggestion of always matching capacity, make, and model goes even a step further. It sure makes sense.

[Chris Hocking]

Hey, what do you know! I did know somethink about the insides of Macs after all! I'll put that down to a lucky guess...

I just had a look at the link Heath posted previously. It confirms what I thought:

In addition, the Mac Pro has two unpopulated 3 Gbps SATA buses for expansion.

So yes, I guess you can set up a 4 drive RAID for your media, have two super drives installed, and still have room for a mirrored systems drive (on the two additional SATA buses).

I can't wait to get the cash together and replace my eMac with one of these beasts! I'll be able to store a hell of a lot of HDV!