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Level 1

5 points

External vs Internal SSD on Mac Pro

Hi,

I'd like to buy a SSD drive for my Mac Pro model 4,1 (2009) Quad 2.66, not to be used for booting OSX but rather audio sample playback. I have a Sonnet PCIe Tempo SATA 6Gb/s installed which I use for eSATA connection to my LaCie d2 drives. Assuming the SSD is a top-performer, I'd like to know if I should connect it to the Sonnet card and have it dangle outside the case, or rather plug it into the spare internal SATA connector which I've heard was available (for the optional second DVD drive) and have it dangle inside. Aesthetics don't matter, it's only a question of performance & possible caveats.

Thanks for your help.

Logic Pro, Mac OS X (10.6.6)

Posted on Aug 5, 2011 8:10 AM

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X423424X

Level 6

14,265 points

Posted on Aug 5, 2011 10:28 AM

Attaching an ssd to eSATA is, IMO, a waste of money since you won't see the full performance of the drive. On the other hand, placing it anywhere on the internal sata is the ideal thing to do. So yes, you can stick it in the optical bay if you wish or any of the other bays if they are free. You need a physical adaptor to convert the 2.5" ssd to 3.5" for the standard bays but some folks have just let them rest, just connected to the cable in the optical bay (no moving parts in the ssd after all). But there are adaptors for the optical bay too if you which to physically screw the ssd into the bay. OWC has all you would need and I recommend them.

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Nawyecky Author

Level 1

5 points

Aug 6, 2011 7:43 AM in response to The hatter

OK, it gets more complicated than I thought.

*Sigh*

The Barefeats page you linked to is very informative and insists on something that I missed completely: the concept of PCI lanes (when is this going to stop, I don't know). That page says the following:

Speaking of price, don't get seduced by the low cost single lane (x1) 6Gb/s host adapters. They may be adequate for HDDs, but SSDs will be hamstrung by the lower bandwidth.

Well, I did get seduced, but that was ages ago (in June...) The Sonnet Tempo 6G card is a PCIe 2.0 x 1 card, which means its maximum bandwidth is indeed 4gbits/s (like you mentioned, 500 mbytes/s) because it only uses one lane (hence the "x1" part). But the PCIe bus can use 4, 8 or 16 "lanes", whatever that may be, with transfer rates pushed up to eleven and beyond (in the figurative sense of course). They are priced accordingly.

OWC confirmed to me that the Sonnet Tempo 6G card will limit a 6G SSD to around 4gbits/s (the speed of a single lane) and will probably see a real world performance of 3gbits/s because of data overhead:

Some users report that the increase also carries a heavy overhead with PCIe 2.0. This overhead works like a bottleneck, and may cause random spikes in the bandwidth. Spikes are especially bad for audio/video work. In these cases, most prefer to stick with the native internal bus.

OWC didn't explicitly mention the lanes issue but crossing their comments with the PCIe specs on Wikipedia and the Barefeats tests seems to confirm that you need at least a "2.0 x 4" controller card to get anything worthwhile out of a 6G SSD.

All this might look like old, obvious news to tech people but it certainly isn't obvious to a musician looking for a fast sample-playback drive...

The hatter

Level 9

60,990 points

Aug 6, 2011 8:31 AM in response to Nawyecky

Try to reassure that your controller plus SSD should be fine.

SATA 2.0 300MB/sec / 3Gb

- 250MB/s actual and possibly what you get from the optical drive bay

SATA 3 500MB/sec / 6Gb/s

SSD 275MB/s SATA 2.0 / or 500'ish and SATA 3 ( 6G device)

Some ideas - sorry may not be Mac OS X compatible, but there are thread on MacRumors.

Mac Pro Rumors

Back to Barefeats and Highpoint RocketRAID for Mac and SSD performance:

http://www.barefeats.com/hard119.html

That is the old 3G card from HPT, this is the new 6G card:

up to 500Mb/s of throughput for enhanced performance - should be fine, definitely better

HighPoint Technologies, Inc -Mac Support

Amazon.com: HighPoint Dual eSATA 6Gb/s for Mac Rocket Dual eSATA 6Gb/s: Electronics

Try what you have and whatever SSD you want to use, now that you have the controller.

Don't let the numbers fool you. SATA 1.0 was only 1.5Gb which is 150MB/sec which is still about as fast as any 7.2k drive offers, but there is 15% overhead on any bus to handle I/O, which is why 300MB/sec comes out around 250MB/sec in real world.

I'd fire off an email to support over at Sonnet - I've found them (for last 15+ yrs) to always be helpful.

External vs Internal SSD on Mac Pro