OS X and SSDs

Draeconis

Draeconis

Draeconis

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28 Feb 2008
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I've been mulling over the prospect of upgrading my Mac with a solid state drive, but there are a couple of things that I'm a little unsure about.

The first is, as I recall, OS X is built to automatically defragment volumes as they're used, but from reading a lot about SSDs, many of them advise never to defrag them, as they don't suffer file fragmentation like conventional hard disk drives.

So, is there a way to disable this auto-defrag function? I'd rather not trash a £400ish bit of equipment through ignorance :P

The second point is more about my Mac specifically. EFI 1.7 was released recently to address the issues of some more modern Macs running their SATA interface at 1.5Gbps, instead of 3Gbps in previous models.

However, I'm unsure how far back this 'Previous Mac' definition goes, as my MacBook Pro 4,1 shows a 1.5Gbps SATA interface in System Profiler.

Inconveniently, the Apple EFI/SMC Updates Page omits the exact model I have, but the EFI 1.7 Apple issue doesn't list my Mac under 'Affected'. Is my SATA connection supposed to be 1.5Gbps, and does anyone know if this will affect SSD performance radically?
 
SATA 1.5 Gbps

It'll cap maximum transfer rates on extremely fast SSDs a bit, but it's not a huge deal. You'd still see all the benefits of SSD.
 
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I'm typing on a MBP3,1 with a OCZ Vertex 120GB.

Instantaneous - even with 1.5Gbit/sec SATA limitation of the old 3,1 chipset.
 
Draeconis said:
The first is, as I recall, OS X is built to automatically defragment volumes as they're used, but from reading a lot about SSDs, many of them advise never to defrag them, as they don't suffer file fragmentation like conventional hard disk drives.
Click to expand...

HFS+ does not automatically defragment nor is it as prone to defragmentation as NTFS for example (in fact some schools of thought say that you actually do more harm defragmenting an HFS+ formatted disk). It's a good filesystem for an SSD.

Secondly I doubt you would saturate 1.5Gbps SATA with an SSD unless you had them in a RAID 0 config.

Just make sure you get the right SSD.
 
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