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Serial ATA and Serial SCSI
aibrahim writes "In the recent Slashdot article about Serial ATA some people wanted to know where SCSI was going, and if Serial ATA could deal with some higher end workstation and low end server requirements. Apparently it has been decided that Serial ATA 2 (pdf doc) and Serial Attached SCSI are the answers."
Now when can I get that 2.5 terabyte RAID1/0 array going?
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The main difference is that Serial ATA will be more readily available first, and will therefore become more popular.
If you look at the Serial SCSI page in the FAQ, note that it is still under development, where motherboards supporting Serial ATA are out now.
Hey, this exact same story was just published in yesterday's slashback.
Wake up, Malda!
a good option to consider. i don't know of any mobo makers that offer it, but it's easy to add on. i think a speed bump to 800 Mbps is around the corner. include the fact that it's hot-swapable, 127 devices or something, etc...
eleven plus two / twelve plus one
...and just as I'm building my fibre channel array for my home computer :-p
Okay...I have a SATA equipped mobo on order which comes in in two weeks. What I want to know is: where are the hard drives? And no, I don't mean the drives that are standard ATA100 that have converters. I mean Seagates native SATA drives. They demoed supposed "production" pieces back in Fenruary.
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Basically, they're extending parallel SCSI technology to address next generation I/O and direct attach storage requirements. It uses the (proven) interface from Serial ATA to avoid an unnecessarily proprietary interface and the costs that usually entails. The naming is unfortunate, because one usually thinks of parallel (side-by-side) as being faster than serial (one after the other) when the technology allows you to combine the two tactics much like in LANs. This is the technology that will enable a new generation of dense devices, such as small form factor hard drives, whereas Parallel SCSI can't because of cabling and voltage issues.
So depending on the pricing of the technology when it hits the shelves/junk mail catalogs, we're going to take a serious look at it. Does anybody have any prototype benchmarks?
Try not. Do or do not, there is no try.
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They need to have a look at perhaps doing some embedded hardware hacks which will allow them less resistance in the SCSI channel on the motherboard as opposed to quantum magnetic research.
WTF?
A likely story, you sat on the "SCSI board", your consultancy domain name is a spammy squatter domain, you cite some BS ratio, you can't spell "resonance".
I may be making an ass of myself if you really do know what you are talking about, but I call bullshit.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
As the Serial ATA PDF points out: ... some of the advanced features of the SCSI protocol were not implemented.
Serial ATA is also expected to be a viable alternative for cost-sensitive entry-level and mid-range server and network storage applications.
So for some or most high-end storage applications, SAS and Fibre Channel will still beat out Serial ATA because you can do a lot more things with the SCSI protocol. Another big advantage of SCSI (in either SAS or Fibre Channel form) is the advantage of many targets to one initiator, or multiple initiators, with current parallel SCSI it's 15/1 and for Fibre Channel it's over 100 to 1 (I forgot the exact number). Multiple initiators aren't supported in Serial ATA II until phase 2, and Ultra 320 SCSI is already faster than the projected 300MBps of phase 2.
I believe the general conception that SCSI is too expensive for the home user is going to make it hard for SCSI to pick up now. Although SCSI is much faster (and better for business in my opinion), I think IDE will continue to rule with it's slower perfomance and cheaper prices the home market. Quite a shame though, IDE seems to always be so slow when compared to the incredibly fast SCSI drives out... but then again, the size of IDE w/ current prices means you can get a huge hard drive for relatively cheap, which is almost impossible with SCSI.
While this is not important (hence my score:0 AC post) i would just like to ask a quick question related to this story topic i have been wondering about, as there tend to be many people on slashdot with more knowledge than i, so maybe someone will have an answer.
Does anyone know if there have been any steps anywhere in the Industry toward the eventual offering of internal hard drives that use FireWire? Would that not be cost efficient?
I dont get it. Are these, like, 40 year old project manager trolls? Or, like, 19 year old scriptkiddie "Nike makes the best shoes, MS makes the best software" trolls?
I wanna know the demographic profile here that for some reason feels threatened by Open Source. Pure curiosity.
"Old man yells at systemd"
remember back when RAMBUS said: we will provide an architecture with very narrow bus but extremely high speed to make up for it? (the *original* RAMBUS specs) -- beside the royalties and whatnot -- it actually (technology discussion only) had merits in that the PCB design was greatly simplified because of less crosstalk, easier routing, etc etc.
and then, people demanded more bandwidth... so now we have double / quad pumped RAMBUS channels -- in the end (today) it's back to 64-bit data-bus *anyhow*... except with an architecture that's not designed for parallel operation.
do anybody see some parallel (ha!) here?
i am guessing (or, predicting) that serial ATA / SCSI will go the same route. i really hope that it won't -- because if it did, our lives will all be kinda rough -- but it probabbly will.
sigh...
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Yup, a SATAN Device (tm).
sorry for the mis-use of language -- what i am refering to is "dual-channel" RDRAM.
it was implemented on intel's i850 (? -- don't remember so well anymore) -- and required two modules to be installed simultaneously.
now that DDR / DDR II is catching up to RDRAM in terms of bandwidth, RAMBUS decided that all the "high performance" RDRAM modules will be "dual channel on a single chip" (which, btw, is 32 bit); now you will say -- this is still small -- but remember that originally RAMBUS can be used with only 8-bit bus width (somebody correct me if i got this wrong); and on the horizon quad-channel (64-bit) RAMBUS is looking at ya. guess how wide is the DDR / SDRAM bus? 64 bits too? ditto.
RDRAM is double-pumped (i do not believe it is a technical term, btw) -- data comes on both pos and neg edge of clock. there is no *real* quad-pumped memory; QDR-RAM is still only double-pumped except both I and O can operate simultaneously. only used in SRAMs anyway. (FYI)
My life in the land of the rising sun.
that serial ATA, while being very fast and much better than what I've got now, will have DRM built in. Is this true? Should I not get serial ATA in my next system because of it? Anyone got any links pertaining to this issue?
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ETHERNET is a protocol; i think what you are really saying is that unshielded twisted pair was able to bump up in speed progressively.
i am not concered with the ATA protocol, in this case -- rather the amount of signals moved through the cables connecting the drive to your board;
even the venerable UTP can only get to 1Gbit and no more; ethernet lives on, 10Gbit ethernet standard is here, but guess what, fibre only.
same with ATA; you can only move so much signal (electrically) through wires. or, signals of so high a frequency; in this case, for a specific type of cable, there in a maximum amount of information that can travel through it. (unless you go out of your way to shield them, etc etc -- but a nicely shielded cable will cost you ~1500 dollars -- most high freq oscilloscope probes uses them, btw.) anyhow; serial ATA tries to bump up speed with a serial interface -- mainly to simplify MB design considerations -- less traces, narrower bus, etc; but since each strand in your cable will only go so far -- i am betting that eventually (without resorting to optical connections) even serial ATA, under the demand of higher throughput either by the market or by their (un)realistic roadmap -- start to double / quadruple the bus width. to me this is just silly -- because the benefit this offered is going away! MB designers will again have to fudge with wide busses and connections.
we might as well just keep on using parallel ATA but boost the signal freq incrementally, since it will get us to the same place in a few years anyway, without all these incremental MBs using different sized busses that's not compatible with different generation drives.
by the way -- PCI bus can only push 133MB anyhow -- anything beyond that is silly
My life in the land of the rising sun.
You're right. Ignoring the quantum stuff, just the fact that he's complaining about I/O bottlenecks on a bus that's designed to support multiple devices is silly. The whole point is that a single device shouldn't be able to saturate the bus.
With current silicon integration levels there is no real reason why SCSI should be more expensive than ATA. They could have just merged them and perhaps emulated braindead ATA on top of SCSI to keep compatibility or something if anyone really wants to.
I'm pretty sure the only reason they keep the difference is to be able to charge more from people building servers. It's purely a marketing and price positioning decision.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
So the serialized interfaces like on the old atari and commodore computers were ahead of their time, granted they were slow?
I agree with this post . . .
Common sense is not so common.
They still don't say that serial ATA will support more than two devices per channel. In fact they say it will be software compatible with ATA in its current form, suggesting it continues the master/slave relationship.
Today's drive media can only reach 40MB/s reading from the platters for short bursts, if their lucky. Normally they'll read/write about 20MB/s. What's the point of another boost in speed of ATA (to the suggested 150MB/s) when you will only ever be able to use 80MB/s of that. Oh, that's right... the ignorant users need bigger numbers on their cardboard boxes to show off to the neighbors.
Does anyone have any information on a HD soon to be released that will offer a quantum leap of read-from-meadia performance to something like 75MB/s? That's more than triple the current read-from-meadia speeds, and they seem to only ever increase the speeds by about 1-2MB/s each year.
SCSI makes sense having very high bus bandwidth, as you can connect quite a few devices and use the connect/disconnect to send simultaneous reads/writes to multiple devices. In that scheme, you can keep most of your drives operating at the same time. Of course Apple has shown that at least for a small RAID, multiple independent ATA channels are just as fast and lower cost than a single SCSI channel. I persoanally have a difficult time thinking that multi-ATA design would scale well to a 32 drive RAID, where a dual channel SCSI would shine.
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SCSI vs Firewire
No master, no slave ... just one lonesome cowboy.
... all in all 1 device per port makes perfect sense, cables are cheap and no problem with drives contending for bandwith or needing to support disconnects in the protocol.
It supports 150 MB/s because its trivial for them to support that speed, because there is only 1 device on the cable signalling becomes very robust. Also there's only 4 pins needed on an ASIC per port, so putting lots of ports on chips is no problem either
My complaint about SCSI is the fact that it's split among so many different implimentations. That means vendors are going to choose to support one, and ignore the rest.
What we need is a single Serial SCSI standard (woo, try saing that a few times). Instead of Fibre Channel, Serial SCSI, Firewire, iSCSI, and whatever else they've come up with, we need one single interface for them all.
If it wasn't for dirvergent implimentations (25/68/80 Pins-Wide/Fast SCSI) people would most likely have SCSI in their systems today, instead of IDE/ATA. ATA retained backwards compatibility, while SCSI gave up compatibility just to get to market with a slight speed boost, as soon as they possibly could.
The other problem with SCSI, configuration and addressing difficulties, will not be an issue with Serial SCSI.
So I'd be happy if I could buy a Serial SCSI card with front-mountable Firewire ports (with more bus power than current Firewire), and perhaps with an option to buy an adapter if I wish to hook that card up to Fibre Channel devices.
Remember, this criticizm is comming from someone who *HATES* IDE/USB.
The SCSI groups REALLY need to unite on this stuff if they want to see any sort of advancement, rather than each ending up as a niche technology. Just look a the Alpha systems. I'm convinced they could have easilly replaced x86 systems. If SCSI groups keep going this way, they face the same ultimate fate.
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