IMac factory installed SSD vs Thunderbolt options

[DeF46]

Careful! The main benefit of an SSD is not so much the maximal transfer speed, but the lightning fast access latency. USB3 has significantly higher latency than Thunderbolt (which is essentially PCI-E). USB3 will work well for lange files transfer, but it will show performance penalties as a boot drive due to the increased latency.

Here is a review of a SSD on USB3.0, presumably an option on the next iMac:

http://thessdreview.com/our-reviews...3-128gb-ssd-review-as-ssd-and-pcmark-vantage/

Latency of a HDD is 9-14ms
Read/write is 80-100 MB/s (near 100 on Velociraptor HDD)

Latency on USB 3.0 is less than 1ms
Read/write is at least double of the HDD on USB3.0

USB3.0 appears to be a significant upgrade over HDD. It's not clear from that review if it's over SATAII or SATAIII.

So yeah latency of SSD on USB3.0 is higher than Thunderbolt, but still better than a HDD.

It's something I would consider myself on the new iMac, perhaps until a good looking, and affordable single drive TB enclosure comes out, at which point I would move the SSD to it, and keep the USB3.0 enclosure for other external backups.

 

[leman]

So yeah latency of SSD on USB3.0 is much lower than Thunderbolt, but still better than a HDD.

I take you mean 'higher' instead of 'lower'. According to this benchmark, the access time for a comparable SSD mounted internally is 0.13/0.2 for read and write, respectively. Thus, the USB3 overhead seems to be around 20%, which is not too bad. It would be interesting to benchmark it with a really fast ssd, like the Samsung 830 series or Crucial m4...

 

[Confuzzzed]

This is an excellent thread, good useful information and work-around suggestions exchanged by forum members with respect and consideration without the usual jingoism and bad manners often exhibited on so many other threads.

 

[DeF46]

I take you mean 'higher' instead of 'lower'. According to this benchmark, the access time for a comparable SSD mounted internally is 0.13/0.2 for read and write, respectively. Thus, the USB3 overhead seems to be around 20%, which is not too bad. It would be interesting to benchmark it with a really fast ssd, like the Samsung 830 series or Crucial m4...

Yep my bad, thanks for the link.

 

[bogatyr]

Just to add: The Seagate TB adapter gets quite warm, even when not being used. I'm not sure if this is normal for all TB peripherals or not. It's been sitting on my desk hooked to my MBA through my TB display, no drive connected.

Also had my MBA shut down on me last night - no messages, just instant black screen. I'm not sure if it was the drive (I was trying to recover data from a bad SSD) or if it was the adapter or a combination of both. It only happened the 1 time. My laptop and the adapter were both scorching hot though.

 

[Mike Valmike]

Careful! The main benefit of an SSD is not so much the maximal transfer speed, but the lightning fast access latency. USB3 has significantly higher latency than Thunderbolt (which is essentially PCI-E). USB3 will work well for lange files transfer, but it will show performance penalties as a boot drive due to the increased latency.

THANK YOU.


I wasn't even participating in this thread but a kind fellow elsewhere on the message board pointed me toward it because I needed to know about the speed characteristics of USB3 and TB external drive arrays. (I thought speed was the issue but from reading your description and comparing to my usage need it is immediately clear that access latency is my actual concern.) And your one response right there just probably saved me a bunch of money and untold wasted time and frustration because I'm going to go ahead and rip the band-aid and buy some sort of LaCie or Promise box (budget is still yet to be finalized) and start popping WD Blacks into it in some sort of mirrored RAID arrangement. I don't need the blazing-fastest RAID 0 that exists, but I need low access latency and rock-solid years of uptime. It looks like TB is my answer.

So once again, thank you. On the nigh-impossible chance we ever meet in person, your drink and steak are on me.

 

[mrparis]

Just to add: The Seagate TB adapter gets quite warm, even when not being used. I'm not sure if this is normal for all TB peripherals or not. It's been sitting on my desk hooked to my MBA through my TB display, no drive connected.

Also experiencing the same level's of heat with my Seagate Desktop TB adapter. Was very surprised with the amount of heat each end of the TB cable it was generating. Just worried about the life of the adapter and Cable as I generally like to keep things as cool as possible.

Was also surprised how hot it got with no drive being attached, I bought my adapter to use as a 'pop in an out' interface with different drives as need endless supply of storage and wanted a quicker solution to FireWire. Working well apart from the heat. Still need to invest in an SSD and try it with an OS attached, but that's for later