blakerwry

Why Are People Buying S-ata?

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Here we come to a common statement...

I was faced with a choice of SATA or SCSI. I could not afford the SCSI solutions available, and for less than half the money am satisfied with SATA

Yes, true... but for even less money you could have a more mature interface that is just as fast.. it's called P-ATA.

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64*66 PCI is 533MB/sec... having 8 top of the line ATA drives wont match that.... You can choose 3ware or you can go LSI... Dell has the CERC as their standard P-ATA RAID controller... which i believe is a rebadged AMI or LSI controller...

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I'll start buying SATA drives when they'll cost same as PATA drives and when they will be native like Seagate.

As for the cable clatter... Yes, SATA cables are thinner, but regular rounded PATA cables are fine if you choose the right length.

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The "rounded" PATA cables are a signal integrity nightmare. I won't even allow them in my office, even in desktop computers. The main buyer of these cables must be people with no understand of electromagnetism at all.

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64*66 PCI is 533MB/sec... having 8 top of the line ATA drives wont match that....  You can choose 3ware or you can go LSI... Dell has the CERC as their standard P-ATA RAID controller... which i believe is a rebadged AMI or LSI controller...

The LSI PATA raid card is 32 bit. All I could find was 3ware at 64/66. It was a consideration, but I ended up deciding 1 very expensive solution was not my path. Especially with a MB with a SATA controller already on the 66 MHz bus. It made very little sense to spend an extra $250 for a PATA card.

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jwb

Explain it to us plz, how round cables affect signal integrity?  :D

taken from here

[...]The longer the cable the longer the signal takes to travel, the more time there is for interference from other signals and for the IDE signals to radiate to other systems. 
[...]
The ATA66/100 cables (Blue connector) use an extra 40 wires that are paired and ground to earth at one end to prevent ground isolation loop from occurring. This pairing of the 40 leads reduces the signal interference between the cables and hence allows for quicker settling times. It is this reduced settling time, now half, that gives the increased data rate.

If you had an oscilloscope and signal generator you could see easily for yourself just how much of the signal passing down one wire is picked up by the one next to it. By putting an earth lead between them that earth's this radiated signal it cuts down on the pick-up of the adjacent cable. Just the same as phone wires are in pairs where one is earthed for the same reason.

So by having a flat cable and putting the most important lines or wire at the extremes you not only have many earth wires between cutting down on interference but also the interference that reaches the furthest line is now weaker because it is furthest away.
[...]
Rounded cables.
From this you can see that bundling up all your cables into a neat round cable does not improve signal transfer along the lines. By doing this you put signal lines next to one another as opposed to having them separated by an earth line. This means that your signals are interfered by all the other signals to quite a large extent.

The consequence being that your error rate increases and thus the number of times data has to be re-transmitted increase all slowing down your data transfer rate. Couple this to longer than 18 inches in length and the errors just multiply.

You might think that putting each line in its own shielding as in your TV line will do the trick. Well yes. But just how big would the cable be for 40 wires? And it must be remembered that there is a compromise between the distance from the wire to the shielding because the shielding actually reduces the signal strength, especially over long distances which is why boosters are fitted in some TV cable applications. The method used in SCSI where twisted pairs are used gives much better isolation and protection over short distances compared to flat IDE cables.

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Iam personally waiting for sata 2.0 to come down the pike before I buy into sata, as the connector will be different, I dont want to be stuck with incompatable drives.

Does anyone actually have some evidence that the basic, internal, one-drive SATA connector is going to change in SATA2?

I checked the press release that described the additions, and while it mentioned new external and multi-device cables, it didn't mention any changes to the internal SATA connector.

Also, if there is definitely going to be a more robust connector used with SATA 2, will it still be possible to connect SATA2 cables/drives/controllers to SATA1 drives/controllers/cables?

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blakerwry you seem to forget that a common motherboard comes with 2 PATA controllers. I believe it's safe to assume that most people have a cd-rom/DVD drive installed in their computer and the majority of these are only capable of running ATA33 - so go ahead and connect your new hard drive to the same controller and you are limited to ATA33 speed.

So you can choose to install 2 harddrives on the other controller but then you won't be able to access these 2 drives independently.

So the way I see it you can only get max. performance out of 1 hard drive on a common PATA motherboard. Or maybe it's more correct to say that you will slow down the multi tasking performance when you have 2 hard drives connected to the same controller compared to the solution where you have only 1 hard drive on each controller (but then we run into the cd-drive problem again).

With a SATA controller your hard drives can be accessed independently as far as I understand.

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ok let's take one thing at a time.

first: Is it incorrect that running a hard drive on the same cable as a potential ata33 cd-drive will limit the hard drive to ata33 transfer rate?

second: I might be way off here but I 'always' had the impression that running 2 hard drives on the same cable/pata controller would limit the performance of each drive in the case where both drives are accessed at the same time. Please correct me if I'm wrong ?

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I would have to completely disagree on the part about rounded cables not being as good as flat cables. Rounded cables use twisted pair connectors which combine the signal and ground. This is much better for noise immunity than flat cables otherwise all Ethernet cables would be flat as Ethernet transmits at a data rate much higher than ATA. I have 34inch round cables working with ata 100 with no problems at all. You just have to get decent cables.

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first: Is it incorrect that running a hard drive on the same cable as a potential ata33 cd-drive will limit the hard drive to ata33 transfer rate?

Yes. The hard drive will transfer data at its normal speed.

second: I might be way off here but I 'always' had the impression that running 2 hard drives on the same cable/pata controller would limit the performance of each drive in the case where both drives are accessed at the same time. Please correct me if I'm wrong ?

You can't access both drives at the same time. ATA buses are FIFO. :) Even if both drives and their controller supported TCQ (not going to happen, sadly), bus arbitration has an irrelevant affect on data transfers because it happens so fast. The ATA bus is even more efficient in bus arbitration (due to its simplicity) than the SCSI bus, and its not even close to an issue on the SCSI bus.

From my discussion here

the actual time it takes the head to move over a track on a 15K drive, assuming it is in position already, is actually dead on 4000 microseconds (not 60). So that, ideally, means control could be handed over to other devices more than 100 times (!) during the reading of a single track (and this is without any seeking, which would greatly reduce the data stream).

To clarify, because that isn't very clear, in the time the fastest hard drive takes to move from track to track (or platter to platter) during a sequential read the SCSI bus can switch control of the bus more than 100 times! The ATA bus is even faster at this... and the drives are much slower (especially at track to track seeks)... Therefore, the only practical limitation on bus performance is the overall bandwidth of the bus and the combined bandwidth of the devices attached.

Additionally, to move beyond theory, you can see here that having two 'simultaneously' accessed devices (RAID 0 striped hard drives) on the same channel has no affect on performance.

There used to be several benchmarks like this in the SR archives before their tragic loss. A lot of data was lost.

The points you enumerated in your post above are some of the most common storage myths on the internet. Like most commonly held beliefs about disk performance on enthusiast sites on the internet (i.e. the importance of STR in real word usage, for example) they are blatant fallacies. But now you know. :)

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Gilbo, you missed one of the major things I got from orchid's original statement. He seemed to be suggesting adding a S-ATA controller because you're out of P-ATA ports on the motherboard...

You could just as easily add a P-ATA controller as you could an S-ATA.

But I am glad to see the other information corrected.

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I just replaced two PATA drives with equivilent SATA drives solely to get rid of Two Molex splitters. My replacement PS got rid of two Molex connectors in favor of SATA connectors: Which is why I needed to use Molex splitters and I hate them with a purple passion. Molex splitters are extremely unreliable.

Grrrrrrrrrrrr

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Well it was a very simple choice for me, when building our storage server...

Cabling 18 disks with P-ata cables wouldve been madness, when Sata both supports greater lenght and alot smaller cables..

And i really dont know what people complain about with the connectors... they are easy to attach and they stay there??

Darking

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Additionally, to move beyond theory, you can see here that having two 'simultaneously' accessed devices (RAID 0 striped hard drives) on the same channel has no affect on performance.

There used to be several benchmarks like this in the SR archives before their tragic loss.  A lot of data was lost.

But isn't the ATA channel locked until the command completes?

I can't imagine that won't decrease performance of the other drive.

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I would have to completely disagree on the part about rounded cables not being as good as flat cables. Rounded cables use twisted pair connectors which combine the signal and ground. This is much better for noise immunity than flat cables otherwise all Ethernet cables would be flat as Ethernet transmits at a data rate much higher than ATA. I have 34inch round cables working with ata 100 with no problems at all. You just have to get decent cables.

Where do you get your cables, DR? I've got several rounded cables -- Antec and some others -- and not a single one of them has twisted pairs. They're simply flat cables slit every five wires, or so, and folded up so they'll go through a sleeve.

I've been looking for cables like you describe for a long time. Where'dja get 'em?

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Well it was a very simple choice for me, when building our storage server...

Cabling 18 disks with P-ata cables wouldve been madness, when Sata both supports greater lenght and alot smaller cables..

And i really dont know what people complain about with the connectors... they are easy to attach and they stay there??

Darking

Other users have other experiences with the cables staying there.

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My drives are all in a stack so I simply got some SATA cables with right-angle connectors on the drive-end and then tied them together as they went down the stack, and tie-wrapped the bundle to the bottom of the case.

It makes a nice, neat package, with each cable helping support the others and keep them from coming loose -- all four would have to come loose at once.

It sure would be nice to have one of those hot-plug chassis's, though. How do they work? Do you plug four (or how many ever) individual cables at some central point on the chassis and then the chassis has its own distribution scheme?

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