: eSATA HDD or USB 2.0 Flash Drive?


staples57
Mar 8th, 2008, 04:40 PM
Need your assistance...

a) Is a USB 2.0 flash drive faster than a 80GB eSATA hard drive?

b) Would a MacBook (Leopard, Core Duo, 1GB) boot/run faster if I were to boot from the internal eSATA hard drive or from a USB 2.0 flash Drive?

Thanks,
Brad

screature
Mar 8th, 2008, 05:02 PM
Need your assistance...

a) Is a USB 2.0 flash drive faster than a 80GB eSATA hard drive?

b) Would a MacBook (Leopard, Core Duo, 1GB) boot/run faster if I were to boot from the internal eSATA hard drive or from a USB 2.0 flash Drive?

Thanks,
Brad

Definitely the the internal SATA. BTW it is only called an eSATA drive when it is external.

It doesn't matter that the USB devce is solid state, you are still bottle necked by the through put of USB 2.0, which is 480 Mbit/s (60 MB/s). Depending on the flavour of the SATA its max through put is either 150 or 300 MB/s

iMouse
Mar 8th, 2008, 05:05 PM
While I have you here screature, how does that compare to Firewire 400 or 800 for through-put??

CanadaRAM
Mar 8th, 2008, 07:11 PM
The USB 2 flash drive is WAAAY slower than a USB2 hard drive, and an eSATA hard drive is faster than a USB 2 hard drive.

Consumer-level flash drives cannot randomly access and write data -- To write one data bit, it has to copy an entire block of data, erase it, make the change to the copy, and then write the entire block back again. That is dead slow in hard drive terms. (the SSD technology in the MBAir is completely different, mondo expensive, and is still not faster than a hard drive in all operations)

Always choose a hard drive for dynamic data that changes many times. Use a flash drive for data transport - write it once, read it once, without a lot of changing going on. Never do editing on a flash drive - always copy it to the hard drive, do you edits, then copy back to the flash


-- the nominal bandwidth of the interface is pretty much immaterial when it is bottlenecked by the througput of the storage device itself (whether flash or HD). FW 400 with a 7200 RPM drive will get you up to 80 MB/s throughput. USB 2.0 with the same drive is lucky to top 40 MB/s. Now we seldom run our machines at full throughput, so there are lots of other factors for real world performance.

Running a single hard drive on a FW 800 or SATA/150 or SATA/300 bus will get you... at most between 80 and 100 MB/s, pretty much similar to what FW400 can do -- because the speed on these is capped by what the drive mechanism can do, not the interface. As drives get higher areal density (that is, able to pass more bits under the heads every rotation), they are creeping up in throughput, the newest drives can hit about 100.

screature
Mar 8th, 2008, 07:15 PM
While I have you here screature, how does that compare to Firewire 400 or 800 for through-put??

Firewire 400 is 400 Mbits/s (50 MB/s) while Firewire 800 is 800 Mbits (100MB/s). The thing to remember when comparing USB 2.0 to Firewire 400 is that it would seem that "theoretically" USB 2.0 should be faster, than Firewire 400, in reality it isn't.

Although high-speed USB 2.0 runs at a higher signaling rate (480 Mbit/s) than FireWire 400, typical USB hosts rarely exceed sustained transfers of 35 MB/s (280 Mb/s), with 30 MB/s (240 Mb/s) being more typical (the theoretical limit for a USB 2.0 high-speed bulk transfer is 60 MB/s). This is due to USB's reliance on the host-processor to manage low-level USB protocol, whereas FireWire automates the same tasks in the interface hardware.

For example, the FireWire host interface supports memory-mapped devices, which allows high-level protocols to run without loading the host CPU with interrupts and buffer-copy operations. Additionally if the USB 2.0 bandwidth is shared wheres Firewire isn't. In other words if your have two or more USB devices running on the same USB 2.0 bus at the same time they share the 480 Mbits/s whereas with Firewire each device will always have a bandwidth of 400 Mbits/s.

So in the real world Firewire, especially 800, is much faster than USB 2.0. So why is it that USB 2.0 is much more ubiquitous than Firewire, well it is like the VHS vs. Beta wars. USB 2.0 has been largely embraced by the PC (Microsoft) world where as Firewire (also called iLink) was a Sony and Apple developed convention. Guess who won the marketing wars?

screature
Mar 8th, 2008, 07:29 PM
FW 400 with a 7200 RPM drive will get you up to 80 MB/s throughput

CanadaRAM, can you explain how this is possible when the max raw data throughput of the Firewire 400 interface is 50 MB/s?

staples57
Mar 8th, 2008, 07:35 PM
Thanks CanadaRAM, the info is much appreciated.

Would the same apply to an IDE to Compact Flash adapter?
The following link is for an adapter that will allow you to replace your internal IDE HDD with a bootable Compact Flash card
Link... IDE CF adapter from Addonics (http://www.addonics.com/products/flash_memory_reader/adidecf.asp)

CanadaRAM
Mar 8th, 2008, 07:51 PM
Thanks CanadaRAM, the info is much appreciated.

Would the same apply to an IDE to Compact Flash adapter?
The following link is for an adapter that will allow you to replace your internal IDE HDD with a bootable Compact Flash card
Link... IDE CF adapter from Addonics (http://www.addonics.com/products/flash_memory_reader/adidecf.asp)

Yes, the CF card will be slow. The bootable compact flash idea is mainly applicable to small dedicated Linux or embedded system installs.

screature:

Sorry, you are right FW800 will get 80 - 100 MB/s best case. FW400 50 MB/s best case. My main point was that the paper gains of SATA/150 and SATA/300 are marginal at best when the mechanism can;t keep up. Now, if you were to put a hardware-controlled RAID device (multiple fast drives, interleaved) at the end of a eSATA cable, then you could see some throughput gain approaching 150 MB/s.

Still Firewire 400 is fast enough to keep up with most single hard drives in use, taking into account how hard drive performance drops off quickly as you leave the outer tracks and start using the inner tracks of the platter (that is -- as you start to fill up the drive).

And as you mentioned, USB 2 suffers from the processor overhead that means it is 30% - 60% slower than Firewire 400, depending on the nature of the transfers.

staples57
Mar 8th, 2008, 07:53 PM
Thanks!

chas_m
Mar 8th, 2008, 09:16 PM
The sheer bulk of wisdom in this thread puts even Wikipedia to shame! Bravo to screature and CanadaRAM for thorough and informative answers that will surely be referenced in the future.

The only thing I can add to this discussion is to expand slightly on CanadaRAM's point that the SSD found in one version of the MacBook Air is a pointer to the future of storage media. I suspect hard drives will be with us for a while yet (maybe 10 years at the most) but SSDs will come down in price and up in quality and capacity and may very well be the future, particularly since you can shape them to be anything you want rather than the fixed form of hard drives.

SSDs should in no way be confused with "flash drives." Same underlying technology, but very different parameters.