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A hard drive that could fully utilize SATA Express?

cbn

Lifer
Mar 27, 2009
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SATA Express has a unique connector with two SATA 6 Gbps ports and a PCIe x2 connection.



How difficult it would be to have an internal storage device capable of using all those connectors simultaneously?

Maybe Multi-actuator hard drive (quad actuator) + NVMe SSD for a single storage volume device?

http://www.tomshardware.com/news/hdd-multi-actuator-heads-seagate,36132.html

We followed up for further clarification. The company responded;
The device shows up as one worldwide name to the user with two access streams available for communication. The drive is one volume but split into two spaces that the user can communicate to. And in the future, if a quad-actuator were implemented (for example), that would be one worldwide name to the user, with four access streams available for communication.
 

Johnny Lucky

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Apr 14, 2012
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www.johnnylucky.org
It is possible but not probable.

The SATA Express standard was a last ditch effort to keep the international SATA standard alive and well. Instead, motherboard manufacturers decided to use the M.2/PCIe standard as an all-in-one solution. Unlike SATA Express, the M.2/PCIe standard can be used in desktop pc's and small portable pc's. It makes sense because small mobile computers and tablets are outselling desktop systems.

The U2 standard is pretty much an Intel initiative that is not gaining popularity among consumers or motherboard manufacturers. The are only a very small handful of motherboards with U2 headers/ports.

Last month I purchased three Z370 high end motherboards for custom builds - one from Asus, one from MSI, and one from ASRock. None of the boards were equipped with SATA Express or U2 headers/ports.

The new PCIe 4.0 standard has been approved. Sometime around the end of the year or early next year we will be looking at M.2/PCIe 4.0 x 8 NVMe solid state drives.

Finally, the current SATA Express headers/ports allow two standard 2.5 inch ssd's to be connected with standard SATA cables. The two ssd's can be configured as individual drives or configured in a RAID 0 array. As ssd performance increases the use of RAID arrays decreases. RAID was originally developed to increase the performance of the first hard disk drives. I bought my first hard drive in 1985. It was a Seagate 10MB drive with an access time of 120 milliseconds. It cost $350.00. It was noisy and not a whole lot faster than the 5.25 inch floppy drives. Back then RAID arrays were more popular than today.
 

cbn

Lifer
Mar 27, 2009
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https://sata-io.org/sites/default/files/documents/Why_SATA_Express.pdf

SATA-IO defined SATA Express host and device connectors. Both connectors are slightly modified standard SATA connectors and are mechanically compatible with today’s SATA connector. This plug compatibility is important, as it enables SATA and PCIe to coexist.The new host connector supports up to two SATA ports or up to two PCIe lanes. There is a separate signal, driven by the drive that tells the host if the device is SATA or PCIe so the host knows what “language” to speak. Thus the motherboard can have a single connector that supports a current SATA drive or a PCIe drive.
So according to info above the drive would have to communicate (in some way) with the host in two different languages.
 

rchunter

Senior member
Feb 26, 2015
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Interesting. I wonder if WD will make drives larger than 4TB. Curious to see benchmarks on that 4TB drive though.
My Asus X99 WS board actually has a couple 2x sata express ports that I don't use. I have 3x Samsung 512GB 950 pros in there. Right now most of my video footage gets edited from those 950 pros and then transferred to HGST He10 drives for archive.
 

Insert_Nickname

Diamond Member
May 6, 2012
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The SATA Express standard was a last ditch effort to keep the international SATA standard alive and well. Instead, motherboard manufacturers decided to use the M.2/PCIe standard as an all-in-one solution. Unlike SATA Express, the M.2/PCIe standard can be used in desktop pc's and small portable pc's. It makes sense because small mobile computers and tablets are outselling desktop systems.

The U2 standard is pretty much an Intel initiative that is not gaining popularity among consumers or motherboard manufacturers. The are only a very small handful of motherboards with U2 headers/ports.
SATA Express as a connector is already dead. It was even dead on arrival, I don't think a single SATAe drive was ever released, though ASUS found a novel use for the PCIe part as a connector for a 5.25" front panel mounted add-in PCIe 10Gbit USB3.1 card.

I must admit I have gotten pretty fond of M.2 in both PCIe and SATA flavour. Because, quite frankly, getting rid of I/O and power cables simplifies so much. I can see U.2 remaining as a high-end option, but I don't find it likely. Even Intel seems to be embracing add-in PCIe cards for storage.

Old fashion SATA1/2/3 is going nowhere for the foreseeable future. It'll likely be here as the go-to traditional mechanical HDD connection for a very long time. No HDD is even close to saturating SATA3. Everything high performance will use either M.2 or a PCIe add-in card. Manufacturers are already beginning to only keep a few SATA SSD models around for legacy systems.

Finally, the current SATA Express headers/ports allow two standard 2.5 inch ssd's to be connected with standard SATA cables. The two ssd's can be configured as individual drives or configured in a RAID 0 array. As ssd performance increases the use of RAID arrays decreases. RAID was originally developed to increase the performance of the first hard disk drives. I bought my first hard drive in 1985. It was a Seagate 10MB drive with an access time of 120 milliseconds. It cost $350.00. It was noisy and not a whole lot faster than the 5.25 inch floppy drives. Back then RAID arrays were more popular than today.
Everyone seems to forget RAID originally stood for "redundant array of inexpensive disks". As you write, it was/is a way to improve performance on the cheap using multiple drives. RAID as a performance enhancer lost pretty much all relevance 10 years ago with the arrival of SSDs.

Of course, if one needs a fast storage system, nothing stops buying a TR/LGA-2066 system and RAID'ing a few PCIe SSDs. Or you could just buy an Optane drive. 500.000 IOPS should be enough for almost anything.
 

cbn

Lifer
Mar 27, 2009
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I can see U.2 remaining as a high-end option, but I don't find it likely.
I do like the compactness of the U.2 motherboard port (shown below), but if there could be such a motherboard port that was modular (PCIe x4, 2 x SATA)* that shared a common drive connector (also accommodating U.2, SATA Express, SAS, SATA) I think would go a long way to increasing acceptance.

*For this I think a U.2 positioned next to two stacked SATA could work. (Maybe call it U.2 Express?)




With that mentioned, looking below I do wonder how much really needs to be added to SFF-8639/U.2 to make it fully compatible with PCIe x 4 and two SATA:

 
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cbn

Lifer
Mar 27, 2009
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Here is SATA Express (prototype) device that uses PCIe x2 + one sata port (as a dual drive):

http://www.storagereview.com/wd_demonstrates_first_pcie_hard_drives



This, of course, as two volumes rather than one combined volume....but it should be possible to make such a device work as single volume. (Eg, Apple's fusion drive and Marvell's hyperduo , Intel Optane Memory, etc.)
Here is a thread I started with software that could make a dual drive operate as one volume:

https://forums.anandtech.com/threads/amd-ryzen-desktops-now-able-to-use-optane-as-hybrid-volume-via-fuzedrive-software.2533123/ (see post #4)
 
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Insert_Nickname

Diamond Member
May 6, 2012
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I do like the compactness of the U.2 motherboard port (shown below), but if there could be such a motherboard port that was modular (PCIe x4, 2 x SATA)* that shared a common drive connector (also accommodating U.2, SATA Express, SAS, SATA) I think would go a long way to increasing acceptance.

*For this I think a U.2 positioned next to two stacked SATA could work. (Maybe call it U.2 Express?)
Well something like that might work, but it adds tremendous complexity to the connector and board layout. I think we're better off with M.2 for mainstream SATA/PCIe drives, and add-in cards for really high performance.
 

cbn

Lifer
Mar 27, 2009
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Well something like that might work, but it adds tremendous complexity to the connector and board layout.
Motherboard manufacturers are already placing two stacked SATA next to U.2:




And the U.2 (SFF-8639) connector already has data paths for PCIe x 4 and two SATA:

 
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Insert_Nickname

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May 6, 2012
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Motherboard manufacturers are already placing two stacked SATA next to U.2:

Dual U.2 implies a very high-end board. There is also only one SATAe port in that configuration. I haven't seen too many mainstream boards feature U.2 ports, and none after Z170 with SATA Express. It seems everyone just went M.2/Standard SATA connector after.

Personally, I don't mind that one bit.
 
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cbn

Lifer
Mar 27, 2009
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Dual U.2 implies a very high-end board. There is also only one SATAe port in that configuration. I haven't seen too many mainstream boards feature U.2 ports, and none after Z170 with SATA Express. It seems everyone just went M.2/Standard SATA connector after.

Personally, I don't mind that one bit.
SATA Express is still around on mainstream boards. For example, this Gigabyte Z370 has three SATA Express.
 

cbn

Lifer
Mar 27, 2009
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Looking at the picture below of the Kingston DCU1000 SSD I got to wondering why not have a SATA Express 2.5" Drive (either 7mm or 9.5mm thick) with a removable M.2 2280 SSD?



This would use less PCB room inside a laptop compared to having a separate M.2 2280 slot and 2.5" bay. Though maybe it could add to the thickness if the drive needed to be 9.5mm rather than 7mm.

Also how about for 3.5" datacenter and enthusiast hard drives? Perhaps not using SATA Express. but an evolution of SATA express? Maybe PCIe x 4 plus 2 x SAS (or 2x SATA)? As mentioned earlier in the thread it does look like the connector would be able to support that.
 
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XavierMace

Diamond Member
Apr 20, 2013
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Looking at the picture below of the Kingston DCU1000 SSD I got to wondering why not have a SATA Express 2.5" Drive (either 7mm or 9.5mm thick) with a removable M.2 2280 SSD?

This would use less PCB room inside a laptop compared to having a separate M.2 2280 slot and 2.5" bay. Though maybe it could add to the thickness if the drive needed to be 9.5mm rather than 7mm.

Also how about for 3.5" datacenter and enthusiast hard drives? Perhaps not using SATA Express. but an evolution of SATA express? Maybe PCIe x 4 plus 2 x SAS (or 2x SATA)? As mentioned earlier in the thread it does look like the connector would be able to support that.
To what end? You seem to have a thing for inventing new solutions then trying to find a problem for it to solve. In your laptop example, you could consolidate an M.2 port and a SATA port into a single SATA Express. Of course you're sacrificing half your capacity and throughput by doing that, which makes it fairly unappealing. That loss of bandwidth makes it even less appealing to the datacenter and the fact that it's SATA rather than SAS makes it completely unappealing. Why bother with "an evolution of SATA express? Maybe PCIe x 4 plus 2 x SAS (or 2x SATA)" when we've already got U.2 and as discussed in one of your other thread, that's already got adoption issues.
 

cbn

Lifer
Mar 27, 2009
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Why bother with "an evolution of SATA express? Maybe PCIe x 4 plus 2 x SAS (or 2x SATA)" when we've already got U.2 and as discussed in one of your other thread, that's already got adoption issues.
U.2 is having trouble in the datacenter? (When I did a brief survey of servers recently it did seem a lot of them had a good amount of 2.5" NVMe bays)

P.S. For PCIe x 4 plus 2 x SAS perhaps we could call that for the sake of discussion "SAS Express". (There is a next Gen SAS coming, not sure what the specs will be though)



Above SAS Roadmap from this Dec 5th 2017 webinar.
 
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XavierMace

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Apr 20, 2013
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I feel like we've had this discussion already. While yes, they're pretty common on systems with 2.5" bays, not so much on systems with 3.5" bays because there's no point. Now you're talking about yet another new interface. I ask again, to what end? There's a reason that WD multidrive you previously posted never launched. Nobody (on the enterprise side) wants a mixed drive like that. The whole reason servers have hot swap bays is for easy drive replacement. If you're putting multiple drives of differing types in a single bay, you've just lost ease of replacement.

So, again, why would I want SATA Express on my servers or this fictional SAS Express? It's the same reason Firewire never took off. The majority of it's functionality could be accomplished using an already widespread existing interface. If you want an enterprise to start adopting a new standard, you've got to give them a REALLY good reason. A lot of people complained when HP/Dell/etc moved from 3.5" drives to 2.5" drives on their mainstream servers. Getting consumers to use a proprietary interface is vastly different than getting an enterprise to use one.
 

cbn

Lifer
Mar 27, 2009
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In your laptop example, you could consolidate an M.2 port and a SATA port into a single SATA Express. Of course you're sacrificing half your capacity and throughput by doing that, which makes it fairly unappealing.
If the SATA Express 2.5" drive is 9.5mm tall it should at least have the same hard drive capacity as a 7mm tall 2.5" tall hard drive. It is true though that by going PCIe 3.0 x 2 throughput is reduced compared to PCIe 3.0 x4....but there are PCIe 3.0 x 2 SSD controllers on the market:

https://forums.anandtech.com/threads/what-nvme-ssds-have-pcie-3-0-x-2-controllers.2533531/

And these PCIe 3.0 x 2 controllers should be fine for lower amounts of NAND or 3DXpoint.

Later with PCIe 4.0 x 2 and PCIe 5.0 x2 a higher amount of NAND or 3DXpoint will work without being bottlenecked.
 
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XavierMace

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Apr 20, 2013
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If the SATA Express 2.5" hard drive is 9.5mm tall it should at least have the same hard drive capacity as a 7mm tall 2.5" tall hard drive. It is true though that by going PCIe 3.0 x 2 throughput is reduced compared to PCIe 3.0 x4....but there are PCIe 3.0 x 2 SSD controllers on the market:

https://forums.anandtech.com/threads/what-nvme-ssds-have-pcie-3-0-x-2-controllers.2533531/
Your argument was to save PCB space. They're only saving PCB space if they're dropping a connector which mean you're limited to one drive instead of two and if PCB is the ultimate concern, M.2 is the smallest connector.

I'm not sure what your point is regarding the controllers. That there's NVMe SSD's slow enough that it doesn't matter?
 

cbn

Lifer
Mar 27, 2009
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Your argument was to save PCB space. They're only saving PCB space if they're dropping a connector which mean you're limited to one drive instead of two and if PCB is the ultimate concern, M.2 is the smallest connector.
I'm thinking 128GB M.2 plus 2TB 2.5" HDD vs. 2.5" SATA Express drive (with 128GB and 2TB combined).

But yeah, a 2TB M.2 SSD would use less space....but I haven't seen too many of these.

I'm not sure what your point is regarding the controllers. That there's NVMe SSD's slow enough that it doesn't matter?
See my edit above....at lower levels of NAND and 3DXpoint there is no gain by going PCIe 3.0 x 4 over PCIe 3.0 x 2.
 

XavierMace

Diamond Member
Apr 20, 2013
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I'm thinking 128GB M.2 plus 2TB 2.5" HDD vs. 2.5" SATA Express drive (with 128GB and 2TB combined).

But yeah, a 2TB M.2 SSD would use less space....but I haven't seen too many of these.

See my edit above....at lower levels of NAND and 3DXpoint there is no gain by going PCIe 3.0 x 4 over PCIe 3.0 x 2.
So you're back to the multidrive again. There's a reason that product never went to market (that preview is 3.5 years old). Either drive goes bad or if you want to upgrade you're now replacing two drives instead of one. For a consumer, it's more trouble than it's worth.

And regarding the controller, you're basically arguing that the SATA Express throughput limitation is fine because some NVMe drives are slow enough that it doesn't matter. That's a silly argument. Bringing up PCIe 4.0 and PCIe 5.0 is pointless because that's not part of the SATA Express spec.

The SATA Express standard is 5 years old and there's been zero widespread usage of it. It's a niche interface. It offers no benefit for spindles and it's limiting for NVMe. The whole point in SSD's is the desire for faster storage, why would you want to see the market adopt an interface that is already too slow for existing drives? Like I said, you're trying to invent problems for it to solve.
 

cbn

Lifer
Mar 27, 2009
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And regarding the controller, you're basically arguing that the SATA Express throughput limitation is fine because some NVMe drives are slow enough that it doesn't matter.
Yes. Definitely Yes. (drives that used that NAND as 384Gb 3D TLC rather than 256Gb 3D MLC were even slower at the same capacity)

Even Intel uses PCIe x 2 for its current Optane memory.

Bringing up PCIe 4.0 and PCIe 5.0 is pointless because that's not part of the SATA Express spec.
I've never found info stating SATA Express is limited to a certain version of PCIe. In fact, the first SATA Express drives used PCIe 2.0 x 2.

https://en.wikipedia.org/wiki/SATA_Express

The choice of PCI Express also enables scaling up the performance of SATA Express interface by using multiple lanes and different versions of PCI Express. In more detail, using two PCI Express 2.0 lanes provides a total bandwidth of 1 GB/s (2 × 5 GT/s raw data rate and 8b/10b encoding, equating to effective 1000 MB/s), while using two PCI Express 3.0 lanes provides close to 2 GB/s (2 × 8 GT/s raw data rate and 128b/130b encoding, equating to effective 1969 MB/s)
 
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cbn

Lifer
Mar 27, 2009
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So you're back to the multidrive again. There's a reason that product never went to market (that preview is 3.5 years old).
I think the main problem was software.

https://www.anandtech.com/show/8820/western-digital-shows-off-a-128gb-ssd-4tb-hdd-35-sata-express-dualdrive

Similar to the Black2 we reviewed last year, the prototype shows off as two separate volumes, although Western Digital is also working on a caching software to make the solution more user friendly.
And check out the description in the Gigabyte sign below:



It is hard to read, but here is what it says:

"Included in our demonstration is work we have done with WD to make the combination of a hard disk drive and flash subsystem look like a single volume to the end user"
However, the same article also noted (at the time) the lack of availability of PCIe x 2 controllers:

To be completely honest, the product as it stands today doesn't make much sense because it's internally SATA 6Gbps, but uses for PCIe for host connectivity. From a performance perspective the only advantage of PCIe is that the SSD and HDD can be accessed at the same time at full speed, but ultimately I think Western Digital has to go with a native PCIe SSD controller to be competitive. Western Digital told me that they are looking into PCIe controllers but since there aren't any available at this point, the prototype is stuck with SATA 6Gbps controllers.
 
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