Most traditional server administrators (including OS X Server administrators) would consider a server running on a Mac mini, iMac, or even a laptop to be silly. But things are changing at a rapid pace, and that which once seemed silly can easily seem like a really good idea. For example, if you have a cart of 40 iPads and you need a server to manage them, then you aren’t likely to find a better combo punch than running Lion Server on a MacBook Air.
But if you are performing computationally complex calculations to render video (as is common with large Podcast Producer environments), then you will more than likely need far more firepower than a workstation with 2 gigs of RAM can net.
The choices you have in front of you for hardware:
Usually the best solution if you can afford it. Apple’s desktop system that comes with plenty of drive bays for hard drives, a RAID card that can be added (which we’ll cover in Storage), two Ethernet ports, optional fibre channel, and a Wi-Fi port.
Apple’s desktop computer with a built-in video screen. Likely only suitable for systems that run a shared workstation that is also a server.
Apple’s most popular server product, a miniature computer that is actually faster than the last version of the Xserve.
Apple’s entry-level laptop offering that comes with solid state drives (making it great to sit atop big old carts of mobile systems).
Apple’s high-end portable computer offering. Still great on top of a cart, but should probably have its lid closed before moving the cart (not that I’m advocating leaving the lid of a MacBook Air open while pushing a cart around a busy school).
Apple once had a rack mount server called the Xserve for those requiring rack density, but no longer sells that product. It is still possible to put any Apple hardware on rack shelves (although a big old iMac might look awkward in a 19-inch rack). The Mac mini is likely one of the more attractive systems to run in a rack, as two can be installed side by side in a standard rack mount enclosure.
Storage is one of the easier items to discuss. But one of the harder items to plan for capacity on, due to the rapid explosion of file sizes and of disk sizes for that matter, is disk utilization. The best way to do this is again with monitoring. By looking at the average increase in storage consumption, you can get a good projection on how much data you will need over time.
One thing everyone with the option should look at is leveraging a RAID to keep data protected. RAIDs are not for backup, but more to keep from having to restore a backup. There are a few different types of RAIDs, which are referred to as RAID levels. These include:
No redundancy, the total capacity is the added storage of all drives that are members of the RAID set. Only use this when you don’t mind losing a disk. The tradeoff is usually faster media.
Full mirror, total capacity is half of a two drive RAID set. Typically used in Mac mini Servers with two drives and with Mac Pro Servers with two drives.
RAID with one parity drive, total capacity is roughly 2/3 to 4/5 of the total amount of data. If any drive is lost, then it is rebuilt with the static parity drive. Not frequently used on a Mac due to RAID 5 and RAID 6 preference.
RAID with one parity drive that is split across a slice of every disk in the raid set. Probably the most common in OS X environments (minimum of three drives).
Same as RAID 5, but with two parity drives. Maximum level of data security in a Mac OS X environment (usually found on Promise hardware, not natively in Apple computers given the number of drives, etc.).
Lower-tiered storage is pretty cheap though. Don’t feel like you need to spend a lot of money today. Buying storage is a lot like buying a car: the second you drive the storage out of the parking lot, it isn’t worth anything (mostly because a drive twice the size is probably going to be out within 24 months). This isn’t to say that there aren’t smart ways to spend on storage. For example, if you are only going to spend an extra $100 on a server to get 3TB drives over 2TB drives, then that’s probably worth the spend.
As referenced in Choosing the Right Hardware, when the system resources for a single server environment exceeds the acceptable threshold for what a single server can do, you will need two or more servers. But how much of a load can one system take before it gets saturated and needs either an upgrade or replacement? Well, that is a tough nut to crack, given that everyone’s data is different: different sizes, different file types, different compression types, different types of network equipment, and even different clients. This makes estimating the exact impact of services pretty difficult.
Apple does not publish information indicating how many servers you need or how many users per server. However, Apple does test each Mac mini Server with up to 36 users using typical home directories. Although you can use far more than 36 users on a mini, the number is dependent on the types of files and how intensely each file type in use interacts with the server. For example, if you aren’t using centralized home directories and instead you are just using iCal Server, you can likely have hundreds of users connect to a single mini. A Mac Pro Server, on the other hand, can often sustain hundreds of users connecting to file shares and interacting with the server regularly with portable or mobile home directories.
Given that most who purchase a server will have access to someone that can assist with appropriate sizing, that is a good place to look for assistance with this conundrum. One option is to work with Apple directly. When purchasing a server, an Apple reseller can guide you through picking the right hardware. Also, members of the Apple Consultants Network can assist if your reseller cannot.
You can spend less than $100 per year to back up your servers, you can buy a Time Machine for a onetime cost of a few hundred dollars, or you can buy a tape library, establish an offsite rotation of the tapes and acquire one of the various software packages to back up your systems. Some options for available software packages include the following:
Time Machine is the tool that Apple includes with Lion (and Lion Server). Time Machine can back up to hard drives, Apple Time Capsules, disks attached to AirPort base stations, and over smoke signals (OK, so not so much on the smoke signals, but it would be pretty cool if it could, right?).
The cloud is the next best thing to smoke signals. CrashPlan is a really intelligently designed solution that deduplicates data (meaning it backs up parts of files rather than complete files each time you make a change to the data) and then backs up the data either to the CrashPlan cloud or to your own disks.
Retrospect is one of the oldest and most mature of Apple solutions. Retrospect can back up to disk and tape.
PresSTORE is another tool that can back up to disk and tape, with a great system used to back multiple clients up.
Two similar products, built for backing up even more data on a larger scale, commonly in cross-platform environments that need specialized agents for Windows and other platforms.
Similar to any number of other Windows-based backup solutions that are Windows-centric but have agents available for Mac OS X and other platforms.
There is much more information on leveraging Time Machine for backing up Lion client computers and Lion servers in Chapter 3.
One of the best parts of choosing software is that you can often get software developers to help you choose hardware that is compatible with their products. If you are backing up to disk, then there is an almost universal compatibility between products. However, if backing up to tape, then you might want to check with the various tape developers to see if there are supported drivers for a given platform.
Once you know what kind of backup storage, then look at how much data changes on a given system each day. The average of this is what you refer to as the rate of change. A full backup of data plus the amount of data per each day whose history you want to store is the amount that each backup set should have in it. For example, if you want seven days of backup and a full backup set is 10 terabytes with a 500 gigabyte rate of change per day, then you would calculate 10TB+(500GB*7) for a total of 13.5 terabytes of data. If you want to always keep one of these sets offsite (and you should in most cases), then that would double the total to 27 terabytes.
Overall, these same general formulas are typically applicable no matter the software title or hardware used. Those 27 terabytes can be disk, tape, or carrier pigeon provided you have the right combination of tools. This even extends to having part of the data in tape and another part in disk. For example, in order to allow for more rapid data restoration, it’s common to do the daily differential backups to disk and the fulls to tape.
Every server should be on an uninterruptable power supply (UPS). The Mac mini Server has very low power requirements. As such, it usually isn’t going to need to have the kind of UPS that powers small cities. But…then again, if you have 500 Xserves, consider something more than an entry-level product from Best Buy.
Let’s start with some numbers:
The Mac mini runs between 10 watts (idle) and 85 watts (maximum) per hour
The Mac Pro runs between 115 watts (idle) and 263 watts (maximum) per hour
The iMac runs between 94 watts (idle) and 241 watts (maximum) per hour
The 11-inch MacBook Air runs at approximately 35 watts per hour (or 50 for the 13-inch)
The MacBook Pro runs between 15 (idle) and 65 (maximum) watts per hour
The UPS devices should run on either USB or a network connection that has client software available for Lion. This is basically included in every UPS built in the past 10 years, so given that the shelf life of most UPSes is lower than most systems that can currently run Lion Server, chances are you’ll use a UPS with support for automated shutdown.
Although it is arguable that MacBook Air and MacBook Pro computers have built-in batteries and do not need battery backup in a UPS, it is still critical to make sure they have ample surge protection.