How to Select Hard Drive Storage for Lion Server Hardware
Apple gives you some hard drive choices when you buy a Mac server to run OS X Lion. The drives vary in capacity, and with some models, you have a choice of rotational speed. You can also replace the hard drive in an existing Mac with a bigger or faster drive.
You may also want to look at two other options for expanded capacity outside the Mac: NAS (network attached storage) and SAN (storage area network), which, despite the acronyms, aren’t opposites.
Disk rotational speed effects Lion performance
Rotational speed is a measure of hard drive speed in revolutions per minute (rpm). This is the speed at which the platters inside the drive spin. The faster the rotational speed, the faster the drive performance.
The lowest rotational speed you’ll find in a Mac that supports Lion is 5,400 rpm, which Apple used in some Mac mini and MacBook models. A speed of 5,400 rpm isn’t particularly speedy for a server, so consider replacing such a drive with the next level up, 7,200 rpm. A 7,200 rpm is also the standard in high-end Mac Pros and Xserves.
The size of a hard drive’s cache is also an indication of drive performance: More is better, but sometimes it isn’t noticeable.
Does Lion need server-grade drives?
You’ll sometimes see a drive labeled with the interchangeable terms server-grade or enterprise-class. Apple uses the first term for the drive in its Time Capsule network storage product and in the drives in Xserve server hardware.
The basic feature of a server-grade or enterprise-class hard drive is a high mean time before failure (MTBF) rating, which represents the average working life of a drive before it needs repair.
The MTBF of some server-grade drives is 1 million hours, which is 114 years! Though not a lifetime guarantee, a high MTBF reduces the chances of hard drive failure during the life of the computer. Manufacturers usually provide longer warranties for server-grade drives, and five-year warranties are common.
A high MTBF rating isn’t a replacement for backing up. Any hard drive can fail at any time. A high MTBF just lowers the failure probability.
Server-grade/enterprise-class drives also feature high performance. This can include more cache, high rotational speed (such as 15,000 rpm), and faster throughput with an SAS interface. However, you don’t need a server-grade drive to get high performance. A server-grade hard drive costs more than an ordinary drive.
Here are two circumstances that might cause you to replace the server Mac’s drive with a server-grade model:
Your network constantly (or frequently) gives the drive a workout, as it might with a large network with dozens or hundreds of users or with a heavily used database on the server.
You need to keep data safe at all costs, and you can’t afford the downtime that restoring data after a failure might give you.
If neither of those cases applies, you don’t need to go out of your way to find a server-grade tag on a drive.
RAID storage for Lion Server
The Mac Pro and Xserve contain multiple drive bays that give you the option to set up multiple drives to work together as a RAID (Redundant Array of Individual Disks) to increase performance or protect data, or both. You can also plug an external RAID box into a FireWire 800 or Thunderbolt port. Apple software supports four types of RAIDs — RAID 0, RAID 1, RAID 5, and RAID 0+1.