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Serial SCSI Standard Coming Soon
rchatterjee writes "SCSI is very close to joining ATA in leaving a parallel interface design behind in favor of serial one. Serial attached SCSI, as the standard will be known, is expected to be ratified sometime in the second quarter of this year according to this article at Computerworld. Hard drive manufacturers Seagate and Maxtor have already said that they will have drives conforming to the new standard shipping by the end of the year. The new standard will shatter the current SCSI throughput limit of 320 megabit/sec with a starting maximum throughput of 3 gigabit/sec. But before this thread turns into a SCSI fanboy vs. ATA fanboy flame war this other article states that Serial Attached SCSI will be compatible with SATA drives so you can have the best of both worlds."
Well, at least we can get rid of those hard-to-route ribbon cables. That alone is worth the switch, IMHO.
Serial ATA Network = SATAN
320 megabytes is about 2.5 gigabits ... which is a lot closer to 3 gigabits than the erroneous 320 megabits figure.
If I understand the title correctly, SCSI = Standard Coming Soon Interface?
Will this new standard be able to do things in parallel the way SCSI can? Will I turn my server into a PC like box that seemingly pauses every time the swap file gets touched?
This is my sig.
If the article meant to say 3GBytes, then how in the world will the PCI *at 64bits and 133MHz, it's 1 GB/sec transfer) bus keep up? Or even RAMBUS memory, which, here says it has a bandwidth of 4.2GB/sec. (So, kinda means you couldn't have more than one SCSI system at a time and get full bandwidth from both.) Now, if you may have to have memory banks for each SCSI component... ick.
I demand a million helicopters and a DOLLAR!
Sure, this definately looks like it could be a great setup: fast, and compatable on multiple systems. But how much will this technology cost? Standard, run of the mill IDE hard drives are about a dollar per Gig. Regular SCSI is a few times higher, especially as drives grow in size. This will be a great advantage if the price range is in the middle of the range, but I doubt that. Now, this won't matter to those with plenty of money to burn on their servers, but would that added price be worth the new types of hard drives? I still don't even see a huge advantage to going Serial ATA right now, so this seemingly good idea could just be another good idea that won't pan out for most users.
take off every sig for great justice
Hopefully this will eventually lead to the elimination of the distinction between ATA and SCSI interfaces. Already the feature distinctions between the two are blurring, hopefully soon the interface will be the same and people will just decide whether they need fast or cheap drives. That would improve the quality of desktop class drives and lower the price on workstation/server drives, as well as make system managment a bit easier.
For more info on Serial attached SCSI check out this page:
n d.html
http://www.lsilogic.com/products/islands/sas_isla
I've only paid attention to HD controllers for the last couple of years or so. But I'm starting to wonder if we're seeing a pattern here. "We'll make everything more efficient by making it serial, and then years later when that's not enough we'll make it paralell to send even MORE data through!"
Anybody think we'll have a massive paralell trend in a few years?
...that the speed limitation on data access is mostly the fault of the DRIVE, not the interface. Show me a drive that can achieve 3 gigabytes/sec and I'll be impressed.
I'll form my OWN solar system! With blackjack! And hookers!
You're mistaken. It's Small Computer System Interface. See dictionary.com
SCSI: Small Computer Systems Interface
descended from
SASI: Shugart & Associates Systems Interface
STOP . AMERICA . NOW
If SCSI is pronounced "scuzzy."
.. "Sassy."
:P
And the full acronym for "Serial attached SCSI" is SASCSI..
How exactly would we pronounce that? Sacksie? Sasky? Oh God, I bet it will be a silent C.
Yay, my computer iss really sspeedy now that I've upgraded to the new SSSASSSSSY DRIVE !@#!@^#^$^$#!
Jason Fisher.
Firewire is low end consumer product...even with its successor (which is taking longer than expected to ship) running at 800Mbits/s (100 Megabytes/second) it falls short of current SCSI technology running @ 320MB/s. As such there is no one who would seriously consider firewire for a large scale server handling many gigabytes/terabytes of data. Firewire is just too slow of a bus for big needs, but does fills its convenience needs in the consumer market. Everything has it's own niche... that's why heavily marked up servers/mainframes/supercomputers still exist instead of cheaper home machines which just can't fill the requirements.
That doesn't matter. Almost everything else in the post is in error. SCSI already has a serial interface standard (and has for a very long time.) -- ever heard of Fibre Channel or Firewire? SATA and SSCSI compatiblity? F***ing duh! What do you think ATAPI is? The SCSI command protocol moving in packets across an IDE physical interface.
I don't know what stupid scheme they are trying to create here -- interface-wise. SATA is a point-to-point configuration. SCSI has always been a bus configuration. If they go the p-t-p route, then it depends on the controller to be able to support the device on the other end -- SCSI crossing the pyhical interface or IDE/ATA/ATAPI crossing it. (Think parallel port ethernet dongle.) I'll have a hard time accepting p-t-p SCSI.
If they want to make SCSI more attractive, they should stop significantly over charging for the technology. They can bulk test "desktop" SCSI drives just as cheaply as IDE drives. They all use the same servo assemblies -- and in some cases, the same basic interface logic (obviously with different microcode.)
There are a couple important notes about Serial-attached SCSI (SAS) that I think are important.
First, SAS uses a point-to-point topology similar to Serial-ATA instead of a shared bus like SCSI. This means each drive has access to full bandwidth, not just one (the bottleneck being the card itself).
Second, according to the SAS working group, SAS comes in three speeds; 150, 300 and 600 MB/s. I'm not sure where that 3 Gbps figure came from.
Third, unlike Serial-ATA or parallel SCSI, SAS is full duplex like fibre channel. This should have some interesting effects on latency.
Fourth, SAS uses the same physical connector as Serial-ATA and in fact can use Serial-ATA drives in legacy mode.
The world is neither black nor white nor good nor evil, only many shades of CowboyNeal.
Serial Streaming Architecture that is. It's a 40MBps serial hardware layer that runs SCSI protocal. It's configured in a loop so there's automatic redundancy in case one link gets disconnected. And a single segment can be up to 20 meters long. Anyone have a Shark (ESS)? It's all SSA inside.
coward
Okay. SCSI lets you do command queuing and reordering. Serial ATA will have this too. Theoretically, if you have a bunch of things doing sequential accesses at once, this can help. SCSI can have outstanding requests to multiple devices on a bus at once, and ATA cannot. This is a pretty big deal for environments where you can have heavy disk load, since if you have two drives on an ATA bus, one can get starved if the other is doing lots of work. I'm not sure if Serial ATA addresses this. For Average Joe's desktop, it's not a big deal because he's usually only doing one thing at once -- loading a game up, or copying a file.
SCSI is generally used to allow price discrimination by vendors. SCSI drives have a reputation for being more reliable, and much more expensive.
SCSI supports many more devices on a bus. This is a big deal to me -- it's a royal pain to buy another controller to add another device or two.
It's unlikely that the two will be merged any time soon, because there's tremendous financial incentive to prevent "enterprise-class" drives from becoming commoditized. SCSI is one of the industry's last useful tools to avoid this.
If you're getting a desktop, use ATA, almost certainly. If you're getting a server with a lot of drives, it may be worth your while to get SCSI, for the abovementioned benefits.
If I had some extra money and just wanted some extra reliability, I'd probably have a mirrored RAID pair of IDE drives, if I were building a desktop without a ton of drives.
May we never see th
There is a good article here
_ 03 -03-03.asp?article_id=211
http://www.snwonline.com/whats_new/sas_and_sata
The article states that the SAS drives won't work on a SATA channel, but SATA drive will on the SAS.
I wonder if mobo makers like ASUS, ABIT, MSI and the likes will choose to have SAS ships on the mobo instead of SATA, as a performance feature?
Lets hope so it would sure open a lot of option for upgrading a PC over time.
FYI - signals do not travel at the speed of light. Somewhere around 50-60% the speed of light in most types of cable.
Overcoming the differences in arrival time of signals in a parallel cable is not significantly more difficult than handling clocking (and maybe clock recovery) and buffering and serial-to-parallel conversion on a serial interface.
The main reason that parallel interfaces were popular years ago when things like SCSI were established was the electronics at the time just weren't very fast. The 74LS00 family logic that SCSI and parallel printer ports were designed around had a maximum clock rate of about 30Mhz. Add in margin for cable noise and distortion and 5-10Mhz was absolutely the most you could manage through any distance. So, if that wasn't fast enough for what you wanted to do, you used more wires in parallel.
These days, it's relatively easy to put multi-gigahertz logic onto chips, and the fewer wires in a cable and connector, the cheaper, so serial wins.
One detail is that SAS is now point to point, just like SATA, and not a bus, but they also indicate that there would be boxes to split a single connection to a bunch of devices, sort of like network hubs. The protocol addresses 128 devices. It isn't clear whether a hub could have SATA devices hooked to it, or if that would require 1 serial channel per device from the host adapter. That is what I understood to be the case for SATA (need one port for each device, no hubs or sharing). The most important protocol difference should be that SAS is still multipoint, even if the connections are point-to-point, so both hosts and adapters need to arbitrate for the bus, while SATA hosts adapters just send out commands and data and wait for the drive to respond on the reverse channel.
It wouldn't surprise me if devices eventually just supported both protocols, and maybe even auto-sensed the type of adapter on the other end. By the time these interfaces get common, I expect the cost differences to be negligible, so It begs the question of why SATA would survive. Because the cost differences are going to be sunk into the chipset designs with almost no marginal cost differences, both system and drive makers will probably save more by reducing the size of their product lines by having one product for both.
Contrary to popular beleif the SATA cables are approx 1mm thick, 6-7.5mm wide and quite "awkward" to work with :(
:(
:(
I for one will be doing my best to hunt down a supplier which makes precise lengths so I can have mine cut to size as they aren't as easy to route as a ribbon cable (seriously!)
Plus if you have 6 devices that's SIX cables in the box instead of 3,... - one of the small shortcomings of SATa
(when I first heard about it, I was under the impression it dasiy chained with an "in" and an "out" port - boy did I think that was FANTASTIC... but I was sorely disapointed when I discovered I was incorrect)