An Unexpected Benefit of Using an SSD and More SSD Tips

I recently put a 250 GB Samsung 850 EVO SSD in my Mid 2007 Mac mini, replacing a failing hard drive. While working on this setup, I found yet one more advantage of using an SSD.

If you use Time Machine, Apple’s free backup utility included with every version of OS X since 10.5 Leopard, you know that it insists on backing up changes every 60 minutes. And you know when it kicks in, because you hear a lot of disk activity and whatever you’re working on is suddenly in slow motion.

Time Machine

Guess what? If you have an SSD, Time Machine does its thing and you hardly notice it. Instead of working with your work hard drive and your backup drive, your Mac isn’t burdened with handling two hard drive directories simultaneously. Accessing the SSD’s hard drive is wicked fast, so Time Machine can discover new and updated files in a flash. And it can read them almost instantly.

There only remains the task of writing these files to your backup drive, which in my case is a 3 TB Seagate Backup Plus USB 3.0 hard drive connected to my 8-year-old Mac mini via USB 2.0. The drive inside is a Seagate Barracuda ST3000, a very responsive 7200 rpm 3 GB/s SATA Rev. 2 drive with a 64 MB buffer. It’s overkill, but it was on clearance, and my 500 GB backup drive had become too small.

Seagate offers a FireWire 800 cable, currently $29 from, and that would require a FireWire 400-to-800 adapter for my Mac mini, so there’s really not justification for the expense, even though FireWire is somewhat superior to USB 2.0. For the amount of data being backed up at any given time, it’s not an issue.

Unfortunately for those still using PowerPC Macs, APM (Apple Partition Map) supports drives up to 2.2 TB, so 2.5 TB and larger drives just aren’t going to work. Stick to 2 TB and smaller to be safe.

Best of all, with this drive I’m ready for that USB 3.0-equipped Mac that I’ll own someday.


TRIM is a very important feature for SSDs. With TRIM enabled, your SSD knows when a file has been deleted and can immediately use its space. Without TRIM, that data continues to exist on your drive and get moved around until garbage collection takes place.

TRIM forces the operating system to release that data right away, not waiting for some future garbage collection cycle. TRIM will always improve SSD performance, which will degrade over time without it.

Unfortunately, OS X versions prior to 10.10.4 don’t support TRIM on non-Apple SSDs. Apple enabled TRIM for them with OS X 10.10.4, but those of us using earlier versions of OS X need another solution.

That solution is Trim Enabler, a $10 system patch that works with OS X 10.7 Lion and later. (For those using 10.6.8 Snow Leopard – as I do on my Mac mini – shareware version 2.2 remains available. I’ll get the $10 version someday when I can put an SSD in my MacBook, which has OS X 10.9 Mavericks and 10.10 Yosemite installed, along with a Snow Leopard partition.)

For those using legacy PowerPC gear, TRIM isn’t available for OS X 10.4 and 10.5. I recommend you look into OWC’s Mercury Pro Legacy drives, which have over provisioning and intelligent recycling of free space.

Have Enough Free Space

I started by recovering a Time Machine backup to a 250 GB external hard drive while I waited for my SSD. 250 GB was just enough, leaving about 30 GB free – and even that’s not enough to keep OS X happy. It’s been nattering at me to free up more space.

I have four iDevices: my current white iPhone 4S, a third-hand 8 GB black iPhone 4S, a 4G iPod touch, and my old iPhone 3GS. The iPhone 4S works with iOS 84.1 and will soon have iOS 9, while the two older devices are forever stuck at iOS 6.1.6. That can get messy with iTunes.

My solution is to sync the newer iPhones to my Late 2008 Aluminum MacBook and the two iOS 6.1.6 devices to the Mac mini. The thing is, I had a lot of iOS apps stored on the Mac mini that I’ll never use on the iPhone 3GS or 4G iPod touch, many of them newer versions not even compatible with iOS 6, so I went into UserName > Music > iTunes > iTunes Music > Downloads. I quit iTunes, put everything in the Trash, emptied the Trash, and relaunched iTunes. It didn’t know the apps were gone right away, but eventually iTunes figured it out.

You can delete old backups in iTunes by going to Devices in the Preferences menu. Choose backups you no longer need, click Delete Backup, and recover a lot more space. Between both of these, I freed up an additional 20 GB of space on my SSD – and no more complaints from my Mac about a nearly full drive!

Yosemite and Third-Party SSDs

With OS X 10.10 Yosemite, Apple introduced kext signing, which checks system drivers to make sure they have not been modified. If they have been modified, Yosemite will refuse to mount the drivers, which means that your Mac running OS X 10 may refuse to boot from a third-party SSD if it modifies Apple’s driver.

The solution appears to be OS X 10.10.4, which adds support for third-party SSDs via trimforce, which you access using Terminal.

For more on this topic, see CAUTION! SSD Drives and Yosemite and Latest OS X Update Allows You to enable TRIM for Third-Party SSDs.

One Last Tip

If you’ve installed an SSD and no longer have a hard drive in your Mac, open System Preferences and choose Energy Saver. Be sure to deselect Put the hard disk(s) to sleep when possible if it’s turned on.

Some Mac users have reported problems with deep sleep and third-party SSDs. With such fast startup times from SSD, it’s probably just as fast and safer to shut down instead of using sleep.


Well, that’s the latest on my SSD adventure. With a startup time of 26 seconds, I’m tempted to shut off my Mac mini when I’m not home. If it weren’t used for AirPrint to our Brother printer, I would, but it’s nice that we can print from our iPhones.

Keywords: #timemachine, #ssdtrim

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