Hitachi Global Storage to Demo First 12Gb/s SAS SSD

[Guest]

Hitachi Global Storage Technology (HGST), which was recently acquired by Western Digital, claims to be first with a demonstration of the first 12Gb/s SAS SSD.

Hitachi Global Storage to Demo First 12Gb/s SAS SSD : Read more

 

[blazorthon]

Isn't SATA 6Gb/s 600MB/s maximum and SAS 6Gb/s equal to SATA 6Gb/s in bandwidth? So shouldn't SAS and SATA 12Gb/s be 1.2GB/s per port? It should take four such ports to hit 4.8GB/s as a theoretical maximum.

 

[drwho1]

are we talking sata 4?

 

[TidalWaveOne]

Since when does 12 Gb/s equal a total bandwidth of 4.8 GB/s? My math must be off (or someone who wrote this piece).

 

[tului]

This is SAS 12Gbps, but I would imagine SATA 12Gbps won't be far behind. Given that the current Sandforce SSDs can saturate 6Gbps SATA now it is needed.

 

[prononbiasedgamerenthusiast]

Sandforce controllers rely on better flash

 

[cbrunnem]

[citation][nom]TidalWaveOne[/nom]Since when does 12 Gb/s equal a total bandwidth of 4.8 GB/s? My math must be off (or someone who wrote this piece).[/citation]

Gb/s is not the same as GB/s

 

[Guest]

this probably refer to sas wide port which consists of 4 ports to achieve 4.8GB/s. For this SSD, i don't think they use wide port, so the theoretically, it can goes as high as 1.2GB/s.

 

[kinggremlin]

[citation][nom]TidalWaveOne[/nom]Since when does 12 Gb/s equal a total bandwidth of 4.8 GB/s? My math must be off (or someone who wrote this piece).[/citation]

As is typically the case with news bits here, this is woefully short on details or expected further explanations.

Peak performance of 6Gb/s SAS is actually 24Gb/s using link aggragation which basically bundles 4 ports together. Like other current serial interfaces (SATA/USB), for every 10bit packet, 8bits are actually data. So out of the theoretical bus transfer limit of 3GB/s, 2.4GB/s would be the usable data transfer rate. Just double this to get the 4.8GB/s rate quoted in this article for the new 12Gb/s SAS standard.

 

[alphaalphaalpha]

For everyone who's wondering, SATA has an 8/10 bit encoding (in order to transfer eight bits of data aka one byte, it encodes that eight bits into a ten bit word for improved error correction), so 6Gb/s in SATA means 600MB/s for real data transfer (MB meaning 1000^2 instead of 1024^2), so 6Gb/s means 600MB/s in maximum theoretical transfer bandwidth. SATA also happens to be full duplex, so it's 600MB/s in both ways (to and from the hard drive).

SATA and SAS have the exact same bandwidths. So, if this is an SAS or a SATA 12Gb/s device, it means that at best, it can transfer at 1.2GB/s. In order for it to have 4.8GB/s, it would need at least four SATA/SAS 12Gb/s ports.

So yes blazorthon, you're right. Another example of an interface that uses 8/10 encoding is PCIe, that is up until the PCIe 3.0 specification which has a 128/130 bit encoding. IE, a PCIe 2.0 lane has a 5Gb/s connection between the two devices on either end, but only 4Gb/s is actually usable for transferring data between either side because the extra 1Gb/s is used for error correction in the data. PCIe has an 8Gb/s connection, but it's change to a 128/130 bit encoding allows it to have an almost double the bandwidth of PCIe 2.x.

Yet another common interface that uses 8/10 is USB.

 

[kronos_cornelius]

Thanks for the discussion on what the speed means commenters. It remains a better choice to just pick a high transfer PCIe SSD since those speeds are well above 600MB/s.

 

[alphaalphaalpha]

Thanks for the discussion on what the speed means commenters. It remains a better choice to just pick a high transfer PCIe SSD since those speeds are well above 600MB/s.

Not everyone wants to spend a huge premium for a PCIe drive when it probably won't help most people (not even most consumer SSD users) much more than a SATA SSD does. The whole point of the SSDs is to be far better than a hard drive. Any improvements after that only help greatly for more specific tasks and are usually not justifiable purchases for most consumers.

 

[madooo12]

it thought to translate Gb/s to GB/s you should divide by 8 not 10 (number of bits in a byte)?

 

[enforcer22]

[citation][nom]cbrunnem[/nom]Gb/s is not the same as GB/s[/citation]

everyone here seems to know that.

[citation][nom]frozonic[/nom]Gb= Gigabit GB= Gigabyte, a Byte is = 8 bits (Byte is a contraction of two words "By Eight") so, 12Gb/s = 1.5GB/s or 1500000 KB/s[/citation]

while not totally accurate this is correct. But i do believe sas uses multi channels so the artical could be correct.

 

[notsleep]

wow. people still use scsi hard drives?

 

[ramicio]

[citation][nom]notsleep[/nom]wow. people still use scsi hard drives?[/citation]

SAS is not the old SCSI you're thinking of. It's uses the same connectors as SATA. It has tons more features. It recognizes SATA drives. It's full-duplex instead of half (SATA).

 

[ramicio]

[citation][nom]alphaalphaalpha[/nom]For everyone who's wondering, SATA has an 8/10 bit encoding (in order to transfer eight bits of data aka one byte, it encodes that eight bits into a ten bit word for improved error correction), so 6Gb/s in SATA means 600MB/s for real data transfer (MB meaning 1000^2 instead of 1024^2), so 6Gb/s means 600MB/s in maximum theoretical transfer bandwidth. SATA also happens to be full duplex, so it's 600MB/s in both ways (to and from the hard drive).SATA and SAS have the exact same bandwidths. So, if this is an SAS or a SATA 12Gb/s device, it means that at best, it can transfer at 1.2GB/s. In order for it to have 4.8GB/s, it would need at least four SATA/SAS 12Gb/s ports.So yes blazorthon, you're right. Another example of an interface that uses 8/10 encoding is PCIe, that is up until the PCIe 3.0 specification which has a 128/130 bit encoding. IE, a PCIe 2.0 lane has a 5Gb/s connection between the two devices on either end, but only 4Gb/s is actually usable for transferring data between either side because the extra 1Gb/s is used for error correction in the data. PCIe has an 8Gb/s connection, but it's change to a 128/130 bit encoding allows it to have an almost double the bandwidth of PCIe 2.x.Yet another common interface that uses 8/10 is USB.[/citation]

It's nothing to do with 1,000 vs. 1,024. It's that there are 10 bits per byte instead of 8.

 

[cirdecus]

[citation][nom]blazorthon[/nom]Isn't SATA 6Gb/s 600MB/s maximum and SAS 6Gb/s equal to SATA 6Gb/s in bandwidth? So shouldn't SAS and SATA 12Gb/s be 1.2GB/s per port? It should take four such ports to hit 4.8GB/s as a theoretical maximum.[/citation]

Yeah i was wondering that too 6000/8 = 750MB/s maximum for SATA3 so you're only looking at 1.5MB/s for this new 12Gbps speed, not 4.8! Silly Toms!

 

[yumri]

what i am wondering is how they came up with the super fast adoption of this technology even if it is fully backwards compatible most likely the severs which will be using it will have to have no SAS RAID cards installed as SAS is usually not a standard feature on any motherboard and SAS cards cost a bundle even with that they just upgraded to SAS 6Gbps if they even did that thus the time for them to do another upgrade will be in like another 5 or so years since sever hardware is built to last alot longer then consumer hardware.
But if the 12Gbps SAS drive is aimed at the consumer market i will be wondering where they are getting consumer boards have a SAS port to hook it up to and even if they do the SAS controller cards are still almost as much as buying another hard drive.
Very good step in hard drive transfer speed but timing is not that good in the development for it. Also how is it in RAID 3, 5, 6, 8 and 10?

 

[blazorthon]

[citation][nom]yumri[/nom]what i am wondering is how they came up with the super fast adoption of this technology even if it is fully backwards compatible most likely the severs which will be using it will have to have no SAS RAID cards installed as SAS is usually not a standard feature on any motherboard and SAS cards cost a bundle even with that they just upgraded to SAS 6Gbps if they even did that thus the time for them to do another upgrade will be in like another 5 or so years since sever hardware is built to last alot longer then consumer hardware.But if the 12Gbps SAS drive is aimed at the consumer market i will be wondering where they are getting consumer boards have a SAS port to hook it up to and even if they do the SAS controller cards are still almost as much as buying another hard drive.Very good step in hard drive transfer speed but timing is not that good in the development for it. Also how is it in RAID 3, 5, 6, 8 and 10?[/citation]

Most servers have SAS connectivity, be it through the motherboard, or through a PCIe RAID card and it's fairly cheap to replace a RAID card if you sell the current one, or at least put it to use somewhere else. It's even better if you just use this drive in new systems instead of upgrading old systems. No SAS drive is aimed at the consumer market. You're not supposed to RAID most SSDs. This has nothing to do with hard drives and is not a hard drive.

[citation][nom]Cirdecus[/nom]Yeah i was wondering that too 6000/8 = 750MB/s maximum for SATA3 so you're only looking at 1.5MB/s for this new 12Gbps speed, not 4.8! Silly Toms![/citation]

Divide by ten, not eight. SATA, like many other serial interfaces, uses 8/10 bit encoding and thus each 8 bit byte of data transferred is transferred as a ten bit byte for improved error correction. So, it maxes out at 600MB/s. SAS does the same. That's why no SATA6Gb/s and SAS6Gb/s SSDs can ever breach 600MB/s. A single SAS 12Gb/s port can hit 1.2GB/s as a maximum theoretical transfer speed. Four SAS ports can hit 4.8GB/s in maximum theoretical aggregate throughput.

 

[WyomingKnott]

On the other hand, the article only refers to interface bandwidth. You need an SSD that can handle data faster than the old interface for this to be really useful. Can the SSD out-perform the existing interfaces?

Not that I'm knocking the development of the new interface. You need both the interface and the storage for a system to work.

 

[Guest]

the raw 4.8Gbps could be a wide-SAS port that uses 2 phys. Each phy could in theory run 12Gbps full duplex. So thats is 1.2Gbps per phy per direction = 1.2Gbps * 2 phys * 2 (sending and receiving). Whether or not the drive can send data for one command and receive data for another command on both phys at the same time could be open for debate.

 

[blazorthon]

[citation][nom]WyomingKnott[/nom]On the other hand, the article only refers to interface bandwidth. You need an SSD that can handle data faster than the old interface for this to be really useful. Can the SSD out-perform the existing interfaces?Not that I'm knocking the development of the new interface. You need both the interface and the storage for a system to work.[/citation]

OCZ has two SSDs that can run at 6GB/s and 7.2GB/s, so it's likely that this one can keep up to 4.8GB/s (practical speed more likely being in the range of 4.2GB/s to 4.6GB/s).

[citation][nom]alc82[/nom]the raw 4.8Gbps could be a wide-SAS port that uses 2 phys. Each phy could in theory run 12Gbps full duplex. So thats is 1.2Gbps per phy per direction = 1.2Gbps * 2 phys * 2 (sending and receiving). Whether or not the drive can send data for one command and receive data for another command on both phys at the same time could be open for debate.[/citation]

All SATA and SAS ports are full-duplex, but then this drive would need to be reading 2.4GB/s and writing 2.4GB/s simultaneously for dual SAS 12Gb/s ports to be fully utilized and give 4.8GB/s. Even then, that's like saying that you move at 120MPH on a 60MPH street just because there are cars going 60MPH one way and cars going 60MPH the other way. They probably meant four SAS 12Gb/s ports, not two, when they said 4.8GB/s.

 

[MichaelDH]

@blazorthon "OCZ has two SSDs that can run at 6GB/s and 7.2GB/s, so it's likely that this one can keep up to 4.8GB/s (practical speed more likely being in the range of 4.2GB/s to 4.6GB/s)."

eh? which SSDs are those, over which bus? OCZ's PCIe SSD cards top out at 2.8 GBytes/sec (ocz.com even confirms this). nobody in the enterprise or consumer end has a single device running at 6 or 7.2 GBytes/sec at this time, nearly a year later. Micron, e.g. has a PCIe SSD rated out to 3.2 GB/s. this 4.8 GB/s Hitachi SSD is a breakthrough, and SAS is the technology to showcase it

anyway, i'm still laughing that RAID means 'redundant array of inexpensive disks' lol! inexpensive!!