Technical questions on eSATA enclosure/drives

[Goi]

Hi,
I'm kinda confused about eSATA enclosure/drives. My experience in external drives is limited to USB2.0, which requires a bridge chip to translate between the USB and PATA interface. With eSATA though, I've read that no such translation is needed? Does that mean that the only difference between eSATA and SATA is the cable/connector? i.e. an eSATA connector from the PC requires an eSATA cable, which plugs into the enclosure's eSATA connector, which then runs another cable or PCB trace to a regular SATA connector, where a regular SATA HDD is plugged into? Are any ICs required in between?

According to wiki and the eSATA white paper, there are differences between the signal levels of SATA and eSATA, and a passive enclosure like the one I've mentioned above would limit cable lengths to 1m. Is that true? If it is, what kinda IC is required for the signal level shifting/compensation?

Also, since eSATA is a signal only specification providing no power, how do external 2.5" drives/enclosures normally draw their power? 3.5" enclosures would have no problem since they require an AC adapter anyway, but 2.5" enclosures are usually USB bus powered. Would 2.5" eSATA enclosures still rely on USB power via a Y-cable?

 

[corkyg]

There is another difference to consider. eSATA externals should connect to an eSATA port. If not, it will be seen as an internal device.

Power is supplied to most 2.5-in eSATA cases by a second USB cable or an independent 5vdc brickette, i.e., a very small A/C adapter. They have a power pin port, and the source can be USB or separate.

I have a 2.5" Firewire external that works the same way. It connects to my laptop's 4-pin (powerless) 1394 port, and it has a power pin port for USB power or separate adapter. I use the separate adapter with the laptop because USB power is more limited.

 

[Goi]

Thanks. So there's no separate IC that does the voltage level shifting in most eSATA enclosures? All they do is convert between the SATA and eSATA cable/connector? Wouldn't that be limited to a total length of 1m then?

 

[corkyg]

What matters is where the source controller is located. A bridge from an internal (mobo) port to an external connector will be seen as an internal SATA device, and write caching will be anabled. You then are subject to Delayed Write Errors. Been there - done that!

1 meter cable length is sort of standard. Addonics touts 2 meters.

eSATA

 

[Goi]

Yes I've read the SATA wiki page. That's where I got to know of the signal level differences as well as how they affect cable length. What bridge are you talking about? Aren't those adapters that fit into a I/O backplate simply converting a SATA port into an eSATA port physically? They don't actually change the signal and do any kind of logical bridging do they? I guess what I'm asking is, what do you need to make a true eSATA enclosure with proper signaling levels, cable length and have the enclosure seen as an eSATA device rather than a SATA device?

 

[corkyg]

You need first an eSATA port on your computer, i.e., the best is a PCI card that has a designed eSATA port on the back plane. A backplane port linking to an internal SATA port won't be truly eSATA, and will be seen as internal. Example:
PCI

In my laptop I use a PCMCIA card with two specifically designed eSATA ports. I simply hot plug my NexStar 3 eSATA case w/drive to it and it is there.

One of these days, we will see eSATA ports on laptops and desktops just like we see USB.

 

[Goi]

OK, but what about on the enclosure side?

 

[corkyg]

Originally posted by: Goi
OK, but what about on the enclosure side?

The enclosure is either eSATA or it is not. Like this:

eSATA

 

[Goi]

So on the enclosure side, the eSATA port gets converted into a standard SATA connector that connects to the enclosed SATA HDD? There are no ICs that do any kind of signal level shifting or translation of the incoming eSATA signal? All the logic is done on the host side? If that's the case it sounds like eSATA enclosures should be dirt cheap since no logic is involved.

 

[corkyg]

Originally posted by: Goi
So on the enclosure side,(1) the eSATA port gets converted into a standard SATA connector that connects to the enclosed SATA HDD? (2) There are no ICs that do any kind of signal level shifting or translation of the incoming eSATA signal? (3)All the logic is done on the host side? (4) If that's the case it sounds like eSATA enclosures should be dirt cheap since no logic is involved.

(1) The eSATA enclosure accepts a standard DATA HDD
(2) There is a PCB in the enclosure
(3) No, the enclosure converts from SATA to eSATA
(4) I think the enclosure is pretty cheap as is.

I will add a picture here in a few minutes to illustrate.

This should asnwer your questions:

eSATA

 

[Goi]

Thanks for the picture.
1) I know the eSATA enclosure accepts a standard SATA HDD.
2) Yup I know the enclosure has a PCB, but I was wondering if there were any eSATA/SATA specific ICs that handle any kind of logic, or is is simply a direct PCB trace from the eSATA port that connects to the PC and the SATA port that connects to the HDD. From your Vantec Nexstar3 picture, it looks like there isn't even a PCB trace, but rather a simple cable that connects the eSATA and SATA connector.
3) This is what I'm confused about. How is it "converting" from SATA to eSATA? It seems to me all the conversion is a physical conversion(connector) rather than a logical conversion(bits and bytes). If I'm not wrong, the only big IC next to the eSATA port handles USB to SATA translation?(either a JMicron or Oxford chip since they're the only people who do these bridge chips)
4) Yeah I guess, and it'd be even cheaper if there was no USB component.

 

[corkyg]

"How is it "converting" from SATA to eSATA? It seems to me all the conversion is a physical conversion(connector) rather than a logical conversion(bits and bytes). If I'm not wrong, the only big IC next to the eSATA port handles USB to SATA translation?(either a JMicron or Oxford chip since they're the only people who do these bridge chips)"

I don't see any "conversion." As far as I can tell it is a wiring/hardware reconfiguration only. This is a good summary that addresses much of what your concerns are:

SATA

 

[Goi]

Thanks corkyg, that cleared things up. I guess none of the eSATA enclosures out there are taking care of the reduced signal levels like I thought they might. Thanks again for your help and patience.

 

[mikedehaan]

Concerning eSATA and SATA, I'm having an issue with some hardware I just bought.

Laptop eSATA ExpressCard:
BT-ECES2

NexStar 3 External Harddrive Enclosure (eSATA and USB 2.0):
NST-360SU-BK

I hooked up my new hardware only to find that it didn't work. The ExpressCard was recognized and installed properly, but the moment I plugged the drive enclosure in, my system froze.

I verified that I had the drive installed properly in the enclosure by using the USB 2.0 interface instead of the eSATA. No problem.

At this point, I was convinced that something was wrong between the eSATA of the drive enclosure and the eSATA of the ExpressCard. So I bypassed the eSATA portion of the drive enclosure by hooking up an external power source to my harddrive and directly connecting the harddrive into the ExpressCard. This worked, but quite messy (pieces everywhere). Not an ideal solution.

Any suggestions? I looked for ExpressCards that were just SATA and not eSATA, but found a lot of discrepancies with advertisements (text says SATA but picture says eSATA, etc).

Thanks,

-Mike De Haan

 

[mikedehaan]

Please ignore my previous post.
I decided to create my own thread instead of hijacking this one (as I should have done in the first place).

ExpressCard and eSATA on a Laptop

My Apologies,

-Mike De Haan

 

[GeezerMan]

On the subject of eSATA enclosures. I'm deciding between the Vantec, has no fan, and the Kingwin, has a fan. Does a fan really extend the lifespan of the drive that much?

Also, if I just use a eSATA bracket on my PC, I know it's recognized as an internal drive, but can it be turned on and off while windows is running? I'm pretty sure it can, since I have read that sata specs allow for hot swapping.

Any big advantages to using a eSATA PCI card instead of a simple bracket?

Thanks

 

[Goi]

I would get one with a fan, coz I don't really like my HDDs running too hot. According to recent research papers, high temps don't really affect drive longevity that much, but there are indications that changes in temps affect drive longevity. In any case, I just don't like high temps.

As for hot swapping for SATA drives, I think it also depends on whether your SATA controller supports it. An eSATA PCI card would obviously take care of the signal level conversion, which will allow for longer cables(2m vs 1m), as well as support for hot swapping. But then you'd also be limited to PCI bandwidth(133MB/s), though that would probably not be a problem.

 

[Zepper]

I received my Rosewill RC-210 controller today. It has a real eSATA port on it. Fully shielded and the plastic tongue with the contacts on it is straight rather than having the hook on the end. My main reason for buying it is that my ingegrated controller doesn't support autonegotiation so I couldn't set my Hitachi drive back to SATA 150 so it would work with my internal SATA controller. IAC, if anyone needs a true eSATA PCI card, this looks like it will fill the bill. According to the manual, whoever actually makes this card has versions that also have a power connector on the slot cover plate. Verry interesting. These are also made in Taiwan rather than the PRC. Another point in their favor, IMO.

.bh.

 

[GeezerMan]

I see the Rosewill RC-210 is a very good price. It's a 1.5 Gb/s. I think my MSI board is a SATA 1 anyway. How much faster in real use is a eSATA enclosure that operates at 3.0Gb/s?
I understand that real world difference is not all that much more.

 

[Zepper]

The mechanics of the drive are the limitation not the interface. Shouldn't notice much real-world diff if any. And the PCI bus maxes at around 100MB/s anyway. You have to have a faster bus to really use the SATA 2 speed.

.bh.

 

[GeezerMan]

Originally posted by: Zepper
The mechanics of the drive are the limitation not the interface. Shouldn't notice much real-world diff if any. And the PCI bus maxes at around 100MB/s anyway. You have to have a faster bus to really use the SATA 2 speed.

.bh.

Would it be noticeably faster just to use an eSATA bracket since I have open sata ports on the board? No limitation of the PCI bus that way

 

[Zepper]

You shouldn't see much diff either way as it is still the drive that's the bottleneck. But you should get better performance than from any other external connection. Some mobos/controllers don't support hot-swap so you may have to use it just like an internal drive: connect and power up drive prior to boot, power off and disconnect drive after powering down your computer. I got the controller because it does support hot-swap and autonegotiate for my new 7K160 drive.

.bh.

 

[GeezerMan]

Thanks for the info..

 

[RalfHutter]

Originally posted by: Zepper
I received my Rosewill RC-210 controller today.

Does this controller card give the external HDD hot-swappability?

 

[Zepper]

RH,
I can say that the 3512 chipset supports hot-swap, but I won't be able to test that capability for a good while as I don't have a true eSATA cable and have no plans to get one at this point. I bought the controller specifically because it has autonegotiate which allows me to use my new 7K160 drive. Which it does. That the chip supports hot-swap, the higher current for eSATA's longer cables, and the card has a true eSATA connector is gravy at this point.

.bh.