- Nick Gold

After having discussed both internal storage options and third-party external Direct-Attached Storage options for Apple’s portable products, it’s time to turn our attention to the desktop Mac Pros. We begin our examination of professional desktop storage by looking at the inside of the Mac Pro tower, and what kind of storage is possible without having to add external hardware of any sort. A number of areas discussed here, namely software-based RAID 0 striped volumes and RAID 1 mirrored volumes, build off of lessons learned in Part 2 of the Storage Primer.

Four Drive Bays

Apple’s last major redesign of the internals of their professional desktop workstation included something many customers had been asking for for many years — more bays for internal hard drives. Not only did Apple increase the number of SATA bays to four, but also introduced a very slick drive carrier system that allows users to mount SATA hard drives into small aluminum sleds, and then slide those sleds in and out of the system without having to fuss with connecting any power or data cables by hand. This has to be done while the system is powered down, but it’s still much easier than on previous versions of the professional Mac desktop machine. Additional sleds can indeed be purchased, so as needed you can swap in and out of your Mac Pro various drives with different sets of data.

Software RAID

Because a user can have up to four drives installed into the Mac Pro’s SATA drive bays at once, a number of possibilities exist for how they can be set up. For instance, some users might just have one large hard drive that can hold Mac OS X itself, their programs, and all user data. But then that user may decide to put a secondary hard drive into the machine to act as a Time Machine backup volume. A video editor may have a startup drive for OS X and applications, and then two or three additional drives set up as a fast RAID 0 striped volume for render files and/or video capture files. A pair of identical SATA drives can be set up as a RAID 1 mirrored volume for very important data to be kept on, data that will still be accessible even if one of the constituent drives has a mechanical failure. WIth four bays available, and the ability to swap out the drives or set of drives that populate these bays at a given time, the sky’s the limit for how you set up your volumes in a Mac Pro.

Secret SATA Ports

You thought four drive bays presented a lot of internal storage options on the Mac Pro? Well surprise surprise, there are actually even greater possibilities due to Apple’s inclusion of two additional SATA ports on the Mac Pro’s motherboard — ports that are not utilized by any of the four drives that might be loaded into a bay proper.

So what’s the use of two extra SATA ports, you might ask, if there are no actual bays to mount drives into associated with them? Where would two additional SATA drives live, inside the Mac Pro tower? This is a valid question that has been answered by a third party called MaxUpgrades, maker of the MaxConnect drive mounting system for the Mac Pro. This device is a mounting chassis that allows you to fill the second, typically unused optical bay slot of the Mac Pro with two more SATA drives. It includes the proper cabling so you can run the SATA ports of those drives to the two extra SATA ports on the Mac Pro motherboard, and also run power cabling to the Mac Pro’s power supply.

Think about this for a moment. A power-user could have a single startup drive for Mac OS X and, say, Final Cut Studio, and then a five-drive RAID 0 striped internal array that could easily benchmark 250 Megabytes a second for read/write speeds. That’s more than enough bandwidth for uncompressed high definition video capture or playback, and many streams of the high def. ProRes HQ codec. Granted a single drive failure will lead to the loss of ALL data on the volume, but if you have a good backup strategy in place, that might not be a big issue.

If you’re looking to take advantage of these extra SATA ports on an existing or new Mac Pro, feel free to contact Chesapeake Systems about selling, installing, and configuring the MaxConnect along with SATA drives. We can also make recommendations on how to best set up volumes made up of single drives, mirrored sets of drives, or striped sets of drives based on your particular requirements.

Hardware RAID

Apple also offers a hardware-based RAID controller that can be purchased for the Mac Pro. Unlike software-based RAID sets that can be created with Disk Utility, a hardware RAID controller can handle more complex forms of RAID such as RAID 5. RAID 5 volumes sacrifice a certain amount of space of all the constituent drives towards parity data. Think of parity data as extra pieces of data that are generated for all the data you store on the system, and help the system recreate lost data in the event of a drive failure. RAID 5 is a good balance between performance and protection, as you do get extra performance from multiple drives working together at the same time as part of a single volume. However you are not sacrificing data integrity, as a single drive failure will not lead to data loss, so long as the failed drive is replaced before the loss of a second drive in the volume.

If you do get the hardware RAID card for the Mac Pro, it’s important to remember that only the drives in the four primary bays can take advantage of it — those two additional SATA ports on the motherboard use a totally separate bus than the bus offered by the card. So with the MaxConnect, you could have a single-drive startup volume on one of the additional SATA ports on the motherboard, and a four-drive RAID 5 array utilizing the four proper bays, with those drives all connected tot he RAID card. For many video editors, this is a safe yet very reasonably priced option for storage, and one that doesn’t require any kind of external array at all taking up more space beyond the large amount of space the Mac Pro itself occupies.

Remember that you need at least three drives for a RAID 5 volume, and that if you do use three drives toward the volume, one of the drive’s capacity will not be available for actual data storage. In a four-drive RAID 5 set, one fourth of the overall space will not be available for actual storage (or one of the four constituent drive’s worth of space). RAID parity data is a little tough to understand for most users, so if you want more information on how the RAID set can be rebuilt when a drive dies, do some searching on Google and Wikipedia. It all really comes down to a handy little logical operation called XOR, and processing these XOR calculations very quickly is what RAID controllers do moment to moment.

This should explain a good number of approaches to internal SATA drive-based storage for the Mac Pros. Because so many bays are present, the possibility of adding more bays, being able to easily swap in and out drives in their little sleds, and the availability of a hardware RAID controller card from Apple, this is a much more complicated area than internal storage on any of Apple’s other machines, which all can only accommodate a single internal SATA drive. For any and all questions this raises, call or email us and speak with one of our Account Executives.

In the next installment of the Chesapeake Systems Storage Primer, we’ll be looking at external Direct-Attached Storage options for the Mac Pro desktops, including eSATA, Firewire, SAS, and fibre channel.