I originally wanted to buy an eSATA expresscard for my macbook pro, assuming that the new port-type would increase sample streaming speed from an external hard-drive.
It’s a matter of different interfaces causing bottlenecks and the hard drive itself is a bottleneck.
Assumption: the external hard drive is not a SSD.
eSATA runs at max 3Gb/s (as the card specifies).
The express card interface runs at max 2.5Gb/s.
When moving from the eSATA interface to express card, you loose 0.5Gb/s
So the card claiming “Data transfer up to 3.0Gbps” is overall invalid. It’ll transfer data at that speed to its internal controller, but not to the computer.
No theory involved. Here’s some data:
A traditional hard drive (not a SSD) has three speeds:
Access time - time it takes to move the read arm into position
Disk to buffer - time it takes to transfer data from the spinning disks to the buffer
Buffer to controller - time it takes to transfer data from the buffer to the computer.
Speed 3 usually runs at the same speed as the controller (SATA)
Speed 1 is usually very small
Speed 2 is the bottleneck. It is always slower than SATA speeds, and even on the fastest spinning drives slower than even USB 2.0 speeds. (Based of Western Digital Velocoraptor drives, sustained @ 200Mb/s)
If the external hard drive is a traditional drive, it won’t perform any faster on eSATA over Firewire 800 or USB 2.0.
It’ll only operate at max the disk to buffer speed. This is true even on internal drives.
Only a SSD comes close to utilizing the speeds that the SATA interface provides.
I hope that it’ll be useful to me. My internal macbook pro hard drive is 5400 rpm, and is running out of space, so I am hoping to transfer some of my larger sample libraries to the external drive. Do you believe that this will increase performance, (7200 rpm over fw800 instead of internal 5400 rpm) or will the 5400 rpm drive act as another bottleneck?
I’m wondering if I could replace the drive inside of the glyph enclosure with a SSD one they increase in capacity and affordability.
A higher rpm drive will always be able to read data faster than a lower rpm drive (unless controller on the drive is junk).
It will increase performance as data will be able to be read faster from the 7200 rpm drive.
Unless some of the data needing to be read is on the 5400 rpm drive, it will be ignored.
The 5400 is nowhere close to utilizing the full speed of its interface.
The 7200 likewise will come nowhere close to utilizing the full speed of Firewire 800, but it will be faster than the 5400 internal.
That disk to buffer speed is always the bottleneck.
I just looked at the Firewire 800 spec
(IEEE 1394 - Wikipedia)
and it outperforms eSATA (3200 Mb/s vs 3000 Mb/s).
But let’s not forget these are MAX values.
It would depend on the implementation in the enclosure (whether it’s a standard SATA connector and SATA power connector).
Also, the hard drive(s) that are in there are probably 3.5". Typical SSDs are 2.5" (laptop drive sized). You wouldn’t want to move it around too much, lest you turn your SSD into bits and pieces.
Okay, thanks again. I will let you know how my new hard drive works. They say that Seagates may not be the best but…I hope that their claims are exaggerated, if even a little bit.
