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The State of Solid State - Chapter II - Opening the Data Highway

Chris brings you up to speed with all things happening in the SSD market.

| Editorials in Storage | Posted: Dec 8, 2009 8:37 am
Manufacturer: TweakTown

Opening the Data Highway

 

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For the first time since I have been involved in computers, a new storage protocol has been introduced after it was needed. Most new products are hampered by the old Chicken or the Egg problem. HDD manufacturers see little need to launch a product until another company launches another product that takes advantage of the HDDs new feature set. In general the most publicized new feature of a new protocol is the transfer rate, a spec that pretty much defines a new protocol. Advancements in timing margins, error correction for better transfer reliability and other small but much improved features are often over looked simply because we have become accustomed to naming a new specification on the speed in which it can transfer data.

 

For the first time, data transfer rate limits have been hit prior to the introduction of a new class of storage products. In our review of the PhotoFast V5 we found ourselves limited by SATA 3Gb/s hardware. Looking back all the way to the transition from ATA 33 to ATA 66, we couldn't find any other product that was available for consumers that had reached the transfer speed limits other than a few instances where burst speed had been improved upon as a direct result of a new protocol. If you read the TweakTown storage articles you already know that we pay little attention to burst speeds since the high numbers shown in benchmarks do not match the user experience and how a system 'feels' to the user. On the other hand, raising the sustained data transfer rates from 240 MB/s to say 330 MB/s is something that the user will notice when moving large files from one place to another, a measurement felt in time, like how long you have to wait for that damn movie to get to a place so you can finally start watching it.

 


SATA / SAS 6Gb/s

 

Our testing of the Seagate 15K.7 600GB enterprise HDD has already shown us that traditional platter drives are capable of taking advantage of 6Gb/s hardware. We are talking about the real deal, no burst speeds. With the same drive on a first generation SAS controller we saw the minimum, average and maximum transfer speeds being for the most part equal. With the same drive on a second generation SAS controller with twice the theoretical transfer limit, we saw maximum speeds increase by nearly 50 MB/s and average STR go up by close to 17 MB/s.

 


PCIe 2.0 RAID

 

LSI and Intel have both launched new PCIe 2.0 RAID controllers with eight PCIe lanes. To keep things simple, just think of PCIe 2.0 with eight lanes like going from PCIe 1.0 eight lanes to PCIe 1.0 16 lanes, like what we had in early video cards with the longer connector. It doesn't work exactly like that, but you get the idea; twice the available highway width means more cars, or in this case data that can pass through, avoiding congestion.

 

No matter how far they open the data highway, RAID will always be limited since the controller makers can add as many point to point (SAS and SATA) drives as they see fit for a product. It is not uncommon to see RAID controllers being offered with 4, 8, 12, 16 and 24 connectors for drives. With today's hard drives we can saturate a 4-drive RAID adapter's data path to the motherboard. By doubling the bandwidth with PCIe 2.0 hardware, we have to move to an 8 drive array before we start to see a ceiling. PCIe 1.0 controllers would give us a STR of around 800 to 900 MB/s to around 1700 MB/s depending on the hardware used. That 900 MB/s limit has been with us for many years and I am happy to see it go.

 


USB 3.0

 

The newcomer to the list is USB 3.0. For years we had to find something else to do while transferring data over USB 2.0. USB 2.0 gave us a real world limit of 30 to 35 MB/s. Hard drives broke this speed all the way back when ATA 100 was introduced many, many years ago.

 

So far we have only tested the Buffalo DriveStation HD-HXU3, the first USB 3.0 external HDD. In our testing we achieved a maximum data transfer speed of 132 MB/s, or a hell of a lot faster than anything USB 2.0 could dream of. The best thing about USB 3.0 is that more speed is available with faster hard drives like the Seagate Barracuda XT and Western Digital Caviar Black for large capacity and just about any solid state drive.

 

When it comes to the user experience, USB 3.0 is going to bring a big smile to the faces of anyone who has painfully sat through transferring anything over 500 MB through USB 2.0 at 32 MB/s.

 


IEEE 1394

 

Created by Apple in 1986, this is commonly referred to as FireWire by everyone other than Sony who chose the name iLink for their consumer products that used the interface. FireWire just won't die, even when Apple has all but forgotten the point to point, serial interface. At its high, IEEE 1394 achieved great success with consumer digital video (DV) manufacturers, but it has been used on everything from external hard drive enclosures to the F22 Raptor.

 

FireWire uses less CPU resources than USB and in its latest form 1394d adds single mode fiber as a transfer medium. 1394d is said to run at 6.4 Gb/s and still has the ability to run over wire. To date we have not heard of anyone making a consumer product with the latest variant of FireWire, so we expect it to gain as much attention as the S1600 and S3200 spec received.

 

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