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SSD vs HDD. Harddrive vs PCI express lanes.

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I am sure someone might have thought on this on too.
Coming from PATA to SATA and its revisions.
Though eventually evolving with PCI express lanes to be used for storage. I am keen to know one thing. As data centers are becoming common these days and server class storage options are probably jumping to NAND storage after all. I wonder what will remain of the disk spinning traditional harddisks.

As we all know SATA as well as SAS from speeds been provided upto 12gb/s and spinning rpm around 15000. For how long will these drives go along ? Even the so called SATA Express isnt widely used. On the other hand introduction of PCIe 4.0 leading to PCIe 5.0 would definitely increase speeds of SSD (nvme) but what about harddrives in particular ?

Why cant harddrives be using the same speeds coming from PCI express x4 ?
In my opinion no matter how good a cell of an ssd is. Traditional harddrive still hold durability over SSD.
 

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Spinning Hard Drives will be here for years yet.
you wont see any increase in RPM
Platter numbers and Density will increase as well as recording methods
But as for spinning speed its going to come down to Physics
best shown example is Optical Drives they have peeked at around 50x ( much higher than that disks tend to spectacularly Explode).
 

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Mechanical and technological limitations would be my guess.


Traditional hard drives read data off platters. They would need to spin at quantum speeds to give you the same speeds as an SSD on PCI-e. And the motor would wear or burn out in no time as well as creating a lot of excessive heat and power draw
 
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Spinning Hard Drives will be here for years yet.
you wont see any increase in RPM
Platter numbers and Density will increase as well as recording methods
But as for spinning speed its going to come down to Physics
best shown example is Optical Drives they have peeked at around 50x ( much higher than that disks tend to spectacularly Explode).
Not that in particular. As far as spinning i guess its fine but what about read/write speeds? I am not considering RAID just the comparing it with nvme drives with high R/W speeds

Think if you replace those NAND in an Nvme drive with a spinning disk. How would that be like ?

Mechanical and technological limitations would be my guess.


Traditional hard drives read data off platters. They would need to spin at quantum speeds to give you the same speeds as an SSD on PCI-e. And the motor would wear or burn out in no time as well as creating a lot of excessive heat and power draw
Ok perceive it like this the sata replaced pata but got limited to 6gb/s that is where it was conventional to use pci express lanes instead of serial ports. What if harddrives would take the same technological advancement as that of nvme ?

If i am not wrong the read/write can improve if these harddrives can be accessed through nvme ?

Correct me if i am wrong or there is some bottlenecks in this. If it were possible as it should be why we just see nvme ssd and not nvme harddrives.
 

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Think if you replace those NAND in an Nvme drive with a spinning disk. How would that be like ?
Ever stood near a jet Turbine spinning at 200,000 RPM That would be your comparison
 

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If i am not wrong the read/write can improve if these harddrives can be accessed through nvme ?
Still comes down to the media access speed.

Yes they can that is what you would use a PCIx sata expansion card for( using a sata hard drive instead of a SSD)
 

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So your point is harddrives cant use pci express lanes ?
Here is your answer.

Ever stood near a jet Turbine spinning at 200,000 RPM That would be your comparison
Do you like and enjoy the constant whine or drone of jet engines cruising at 140dBA?

Corsair SP120 fans at 2350rpm which 99% of us claim are too damn loud are rated at 35dBA. I'll let you do the math.
 
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Hmm interesting yes. So the OP thinks by connecting a HDD to a PCIe lane will improve the reads/writes? Hmmm I'd test that when I find a Card that can do so. Still wouldn't the rpm be the cause of the reads/writes or is it the Sata connector?
 

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Though eventually evolving with PCI express lanes to be used for storage. I am keen to know one thing. As data centers are becoming common these days and server class storage options are probably jumping to NAND storage after all. I wonder what will remain of the disk spinning traditional harddisks.
They use non-volatile chips as caches but bulk storage is still on disks and that is expected to remain true (only growth area forecasted in HDDs). Price per GB, disks are cheaper and thanks to physics, that will remain the case. Disks also have much higher endurance and reliability. SAS 12 gbps is more than sufficient for 14+ TB HDDs.

Why cant harddrives be using the same speeds coming from PCI express x4 ?
Because they usually only have one read/write head that can only read or write to one position on a single platter at a time. The maximum they can operate is something like 300 MB/s (2.4 gbps) unless there's some breakthrough in the works.


If they left the 3.5" form factor, they could probably pack at least four heads on a drive quadrupling bandwidth. Additionally, more complex controllers could write to each platter individually so if you have 5 platters, you could get roughly five times the performance there too (combined, 20* performance or 6 GB/s). But why when RAID does pretty much the same thing in software and adds redundancy on top? Fundamentally, I don't think there's a market for super complex hard drives because their costs would exceed that of an SSD with a lot of extra points of failure.
 
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The way a HDD works limits its speed. This is why 7,200RPM hard drives have not even come close to using all the speed that SATA provides.

The reason being that the hard drive can only read/write the bit of data that is directly under the read/write head. And the drive can only but so many of those bits under the read/write head in a given amount of time. Changing the interface that the hard drive uses from SATA to PCI-E does not change the number of bits that the drive can move under the read/write head in a second.

However, because NAND flash storage, like SSDs do not have to physically move the bit under the read/write head, they can achieve much higher speeds. The wait time between reading/writing two different bits of data is much much lower on SSDs.
 
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Still comes down to the media access speed.

Yes they can that is what you would use a PCIx sata expansion card for( using a sata hard drive instead of a SSD)
Leave the Sata barrier aside. Im taking about a controller that would use spinning disk instead of nand flash storage and provide optimal read/writes through pci express lanes

I know i may sound crazy but dont you think it should be taken into consideration as the future is pci express and its usable lanes.
 

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Leave the Sata barrier aside. Im taking about a controller that would use spinning disk instead of nand flash storage and provide optimal read/writes through pci express lanes

I know i may sound crazy but dont you think it should be taken into consideration as the future is pci express and its usable lanes.
SATA and SAS were literally designed as PCI Express -> hard drive interconnects. NVMe was created because SATA/SAS had a lot overhead that was irrelevant for non-volatile memory chips.

The CPU, using NVMe, can pretty much directly read/write to NVMe chips. With hard drives, it's never direct because there's micromanagement in each HDD controller that has to move the head and read/write as the platter passes under it. Hard drives are advertised as having memory (e.g. 256 MB). That's the cache where the CPU actually talks with while the controller moves the data to and from the cache. SATA/SAS takes all of these intricacies into consideration.
 

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Leave the Sata barrier aside. Im taking about a controller that would use spinning disk instead of nand flash storage and provide optimal read/writes through pci express lanes

I know i may sound crazy but dont you think it should be taken into consideration as the future is pci express and its usable lanes.
That's already how it is set up, for the most part. Because a single PCI-E lane has enough bandwidth for multiple hard drives, they connect a SATA controller to a single PCI-E lane and run multiple hard drives off that one PCI-E lane through the SATA/SAS controller.
 
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Hmm interesting yes. So the OP thinks by connecting a HDD to a PCIe lane will improve the reads/writes? Hmmm I'd test that when I find a Card that can do so. Still wouldn't the rpm be the cause of the reads/writes or is it the Sata connector?
Unfortunately you cant. There is no controller(on hdd) as far as i know that uses pci express lanes instead of sata. I am just making it simple as possible. Ok take an example Samsung 970 evo nvme drive but it has spinning disk instead of those TLC. If it was possible because it should be harddrive would have good r/w speeds and sata would have been eliminated though ssd market should not be in the same position as it is right now. Of corse tech giants would have never allowed that

SATA and SAS were literally designed as PCI Express -> hard drive interconnects.
But still cant get those good read/writes anyway. Bottleneck is still there Mr. Pie eater :p
 

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Ok take an example Samsung 970 evo nvme drive but it has spinning disk instead of those TLC
You'd end up with a drive that was insanely slow relative to the TLC based 970 Evo, and no faster than a SATA HDD.

That's the point we are trying to make. SATA isn't the bottleneck, connecting a HDD directly to PCI-E will not make it any faster, not one bit. The spinning disk is the slowest part, and it alone determines how fast the HDD will be.
 

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But still cant get those good read/writes anyway. Bottleneck is still there Mr. Pie eater :p
SATA/SAS aren't the bottleneck with HDDs, the capabilities of the read/write head are.

Let's pretend that the read/write head somehow managed to cache all of the requested data in the drives controller before the request for that data is made. This is about the only scenario where the drive might get bottlenecked by SATA 6 gbps. This is extremely rare though and that burst of data ends as fast as it starts because the head has to go fetch the rest of the data.


If you're not familiar with what a hard drive head is...
 
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You'd end up with a drive that was insanely slow relative to the TLC based 970 Evo, and no faster than a SATA HDD.

That's the point we are trying to make. SATA isn't the bottleneck, connecting a HDD directly to PCI-E will not make it any faster, not one bit. The spinning disk is the slowest part, and it alone determines how fast the HDD will be.
Nope! certainly not correct. You see it all depends on the controller. If you know it was not possible to exceed speeds above 6gb/s on serial ata so alternates were introduced resulting in using pci lanes doubling the bandwidth but then came these ssd from intel and the market had to switch. Im not saying it cant but it should be. Sata should be dropped and traditional hdd should adopt nvme.

SATA/SAS aren't the bottleneck with HDDs, the capabilities of the read/write head are.

Let's pretend that the read/write head somehow managed to cache all of the requested data in the drives controller before the request for that data is made. This is about the only scenario where the drive might get bottlenecked by SATA 6 gbps. This is extremely rare though and that burst of data ends ass fast as it starts because the head has to go fetch the rest of the data.


If you're not familiar with what a hard drive head is...
That is where the spinning speed comes in. 15k rpm and you might as well know SAS supports now upto 12gb/s yet still no drives seems to be that common as its still slow as compared to nvme..
 

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Nope! certainly not correct. You see it all depends on the controller. If you know it was not possible to exceed speeds above 6gb/s on serial ata so alternates were introduced resulting in using pci lanes doubling the bandwidth but then came these ssd from intel and the market had to switch. Im not saying it cant but it should be. Sata should be dropped and traditional hdd should adopt nvme.
Ok, let me put it another way using real world examples.

Let's take the 6TB WD Black Hard drive. This is one of the fastest consumer SATA hard drives on the market.

SATA 6Gb/s can transfer data at 600MB/s.
SATA 3Gb/s can transfer data at 300MB/s.

The maximum speed the WD 6TB Black Hard Drive can transfer data on or off of the spinning disks inside the drive is only 218MB/s. This spec is given my WD themselves.

It doesn't matter if the drive is using SATA 6Gb/s, or even SATA 3Gb/s or even if it was a SAS 12Gb/s or a PCI-E x1 connection, the drive will still only transfer data at 218MB/s period. Changing the controller on the drive from SATA to PCI-E will not change the speed of the drive at all. Data will only flow at the speed of the slowest component, and the transfer rate to and from the disks inside the HDD will always be the slowest component.
 

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That is where the spinning speed comes in. 15k rpm and you might as well know SAS supports now upto 12gb/s yet still no drives seems to be that common as its still slow as compared to nvme..
15,000 RPM drives are pretty much gone, replaced by SSDs. The reason why they existed and the reason why they've been replaced is simple: access times.
15,000 RPM = 2 ms
10,000 RPM = 3 ms
7,200 RPM = 4.17 ms
5,400 RPM = 5.56 ms

This is the amount of time it takes for the drive to make a full rotation. The faster it spins, the faster the head and platter will be in position to read/write.

SSDs have access times lower than 2 ms because there's no mandatory waiting.

This is why 15,000 RPM and 10,000 RPM drives are virtually gone from the market except in critical applications where data reliability is more important than access time.


Keep in mind that 15,000 RPM and 10,000 RPM drives have smaller diameter platters because physics make the platters warp due to centripetal force. Even though they have improved access times, they have significantly lower capacity and potentially lower peak bandwidth (because angular velocity at the outside ring of the disk is close to the same across 15,000, 10,000, and 7,2000 RPM drives).

In other word, physics strikes again.
 
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Oh now i get it. So why they even invented that 12gb/s SAS controller anyway ???
Just to get those SAS SSD perform upto mark ? Still ssd i dont think have a life span better then spinning disk ? No ?
 
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