It may depend a little on what the external drive's enclosure maker chose to do. But the truth is that the electrical signals and timing and almost everything are the SAME for SATA and eSATA - well, except that eSATA uses slightly higher voltages and tolerates more noise and weaker signals on the data lines so you can use a longer cable - so the simple design does NOT involve extra circuitry and processing delays. Hence many tests I've seen show that a good eSATA unit works at the SAME SPEED as an internal SATA drive.
Thank you for your prompt reply. Obviously, there are many variables involved which I didn't explicitly state (e.g. OS, PCI vs PCI-e vs MoBo). For the record, in case you wish to follow-up I'm working up the specs for a new NLE/transcoding & was wondering if noticeable performance improvements will be seen if box is stuffed with internal drives as opposed to quickly swappable external drives.
Best,
/mp
Best,
/mp
The results of eSATA are dramatic and with no protocol overhead issues as with USB or 1394. The eSATA storage bus delivers as much as 37 times more performance. This ability is perfect for using an array of drives with performance striping behind the eSATA host port. 
For what you want to do I suggest the best way to connect HDD's to your system is probably SATA II ports on the mobo, and LOTS of them. So look for a mobo with as many SATA II ports as you can get. This might be done by having TWO basic SATa controllers. There is always one in the mobo's southbridge chip, but some mobos have an additional SATA controller chip to give you more ports.
You can always add more SATA ports by adding a SATA controller via the PCI bus, BUT they will be a little slower because of that PCI bus itself.
I can see the appeal of many external HDD's you can swap in and out, but watch out for two things. First, you MUST have hot-swap support; that feature IS part of any true eSATA controller port, but not necessarily provided by an internal SATA port that is "converted" to eSATA via a plain connection adapter. So your issue may become getting a mobo with many eSATA ports built in. Most I have seen only have one or two, expecting them to be used mainly as backup devices. You may, however, find an eSATA card to mount in a PCI slot that gives you many true eSATA ports externally accessible. The impact of using the PCI system for this will be minimal compared to the speed advantage of eSATA over other external connection systems.
As for the new 6Gb/s SATA, there are few systems that can actually use a speed faster than SATA II, so the advantage of the newest systems has yet to be exploited.
USB2 systems usually include a safe procedure to force complete writes and file closure before disconnecting them - that icon for "Safe to Remove ..." BUT USB2 data transfer speeds are typically only half or less of the speed of modern eSATA, so may not meet your needs. I can't say much about the newest USB that's coming, except that its specs say the speed will be good.
For transcoding and video editing, some of the better software packages can actually use large amounts of RAM and show definite speed-ups if it is available. Check for sure in the specs and reviews of what you are considering. If you do get a package that uses lots of RAM, you MUST go with a 64-bit OS. No 32-bit OS will let you use more than about 3GB or system RAM; current Win 7 64-bit allows over 12 GB RAM.
Consider also the choice of CPU. For doing transcoding and other tasks simultaneously, you really should look at a fast CPU and especially at 3 (minimum) or 4 cores. That also impacts your OS and app software choices. Make sure the app software can and will use multiple processor cores effectively.
You can always add more SATA ports by adding a SATA controller via the PCI bus, BUT they will be a little slower because of that PCI bus itself.
I can see the appeal of many external HDD's you can swap in and out, but watch out for two things. First, you MUST have hot-swap support; that feature IS part of any true eSATA controller port, but not necessarily provided by an internal SATA port that is "converted" to eSATA via a plain connection adapter. So your issue may become getting a mobo with many eSATA ports built in. Most I have seen only have one or two, expecting them to be used mainly as backup devices. You may, however, find an eSATA card to mount in a PCI slot that gives you many true eSATA ports externally accessible. The impact of using the PCI system for this will be minimal compared to the speed advantage of eSATA over other external connection systems.
As for the new 6Gb/s SATA, there are few systems that can actually use a speed faster than SATA II, so the advantage of the newest systems has yet to be exploited.
USB2 systems usually include a safe procedure to force complete writes and file closure before disconnecting them - that icon for "Safe to Remove ..." BUT USB2 data transfer speeds are typically only half or less of the speed of modern eSATA, so may not meet your needs. I can't say much about the newest USB that's coming, except that its specs say the speed will be good.
For transcoding and video editing, some of the better software packages can actually use large amounts of RAM and show definite speed-ups if it is available. Check for sure in the specs and reviews of what you are considering. If you do get a package that uses lots of RAM, you MUST go with a 64-bit OS. No 32-bit OS will let you use more than about 3GB or system RAM; current Win 7 64-bit allows over 12 GB RAM.
Consider also the choice of CPU. For doing transcoding and other tasks simultaneously, you really should look at a fast CPU and especially at 3 (minimum) or 4 cores. That also impacts your OS and app software choices. Make sure the app software can and will use multiple processor cores effectively.
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