Question About SSD Support - Dell Precision 7550

Hello ElevenForum. I have another question that maybe someone can answer for me.

I was looking into what my system, for which the specs are listed below in the My Computers section, can support for SSD drives. According to Dell's own documentation for this system, it can support up to 2TB M.2 2280 NVMe SSDs if they are class 35 drives, but only up to 1TB if they are class 40 or class 50. Now, I'll admit I don't know that much about SSDs and what these classes mean. If I'm not mistaken, that has something to do with transfer rates and/or IOPs rating, right? Why would the class of the SSD make a difference to supported capacity, and why wouldn't my system support up to a 4TB drive?

For reference, the M.2 interface for drives in my system is PCI-E Gen 3x4. I know that Gen 4 drives are backward compatible with it, as my secondary SSD, which I use for a data drive, is a Samsung 980 Pro.

I don't plan on adding a 4TB drive to this thing, as I do not need that much space. It's just me being curious why there are these limitations. Perhaps someone who knows a lot more than I do would be able to clear this up for me.

EDIT:

For context, I was looking this up because I am thinking of replacing my OS drive with something a little better. While CrystalDiskMark rated the Kioxia drives maximum throughput on read at 3000MB/s (which, if I'm not mistaken, is not far from the max for Gen3x4), its write rate is around 2000MB/s, and the IOPS rating both ways is less than 100K, while the 980 Pro is much higher at 3000MB/s write and 350K IOPS. From my understanding, the IOPS rating is what shows how well the drive performs with small files, so a drive with higher IOPS will boot a bit faster and load applications faster. I'm thinking of replacing the Kioxia with a 980 Pro or another drive of equal performance. I run a Linux VM off of my 980 Pro Data drive, so I don't want to simply swap the drives around.

I'm unfamiliar with SSD "class". A little Web searching suggests that it's unique to Dell, rather than an industry standard.

I wonder whether the Dell spec on the laptop is based on compatibility, or is just a list of configurations they sold?

ArazelEternal said:

it can support up to 2TB M.2 2280 NVMe SSDs if they are class 35 drives, but only up to 1TB if they are class 40 or class 50. Now,

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Mainly, they’re talking about the power consumption (or power class) of the NVMe drives.

Class 35 are low-power SSDs, drawing less power than Class 40 or 50 SSDs. This allows them to be supported at higher capacities (up to 2TB) because the system can manage the heat dissipation, power consumption and other thermals better when the drives are more power-efficient.

Class 40 and Class 50 stands for higher-performance SSDs with greater power requirements. These typically have higher throughput (faster read/write speeds), so they draw/need more power and generate more heat. That’s why your system is limited to 1TB on these higher-performance SDDs - as it can struggle with the power and cooling requirements of a larger drive at full performance. Another way to put it... your system's motherboard and the power delivery circuit may be optimized for lower-power SSDs - so a larger more power-hungry SSD - could lead to instability or throttling.

neves said:

Mainly, they’re talking about the power consumption (or power class) of the NVMe drives.

Class 35 are low-power SSDs, drawing less power than Class 40 or 50 SSDs. This allows them to be supported at higher capacities (up to 2TB) because the system can manage the heat dissipation, power consumption and other thermals better when the drives are more power-efficient.

Class 40 and Class 50 stands for higher-performance SSDs with greater power requirements. These typically have higher throughput (faster read/write speeds), so they draw/need more power and generate more heat. That’s why your system is limited to 1TB on these higher-performance SDDs - as it can struggle with the power and cooling requirements of a larger drive at full performance. Another way to put it... your system's motherboard and the power delivery circuit may be optimized for lower-power SSDs - so a larger more power-hungry SSD - could lead to instability or throttling.

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That makes a bit more sense, thank you.

So it isn't like the system wouldn't recognize a 4TB drive, but more that it might draw more power or generate more heat than the system is designed to handle. That seems odd considering that the Precision 7000 series is designed to be very high-performance CAD and data analysis machines.

The Hynix Gold P31 2tb and Samsung 990 evo are supposed to be two of the most power efficient (ie run cooler). Not the 990 evo "pro" just the straight 990. Of the two, I think the P31 is supposed to be the coolest. Also the WD Black SN7100. You could also add one of these.

thermal silicone pad

And yet Crucial offers 4GB SSD upgrades. That includes a Gen5 version, which would be both expensive and pointless. It suggests that delivery of power to the NVME drive isn't an issue, though.

The spec's for the 980 Pro may be of interest. Or the 4TB 990 Pro 2. (It's available without a heatsink.) The power draw varies with capacity, but it's not anything like proportional to capacity.

I wish that I could supply all the details you need to make an informed choice.

ArazelEternal said:

So it isn't like the system wouldn't recognize a 4TB drive, but more that it might draw more power or generate more heat than the system is designed to handle. That seems odd considering that the Precision 7000 series is designed to be very high-performance CAD and data analysis machines.

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Depends, taking into account the age of your system - 512 GB SSD was standard back then, 1TB SSD was more commonly seen only on premium machines (let alone 2TB). So, it's possible - that the original datasheet for Dell precision 7550 was not updated (to include 4TB SSD - which became more accessible couple of years after this system was released). On the other hand - it's also possible - to have a BIOS/Firmware limitation of 2TB (respectively 1TB - as specified in the datasheet).

As bobkn mentioned above - Crucial supposedly tested your model with 4TB SSDs and it's suppose to work (labeling them as compatible). Tho, it wouldn't be the first time - a brand labeled their product as compatible with a specific machine - only to find-out it doesn't (due to a BIOS/Firmware limitation). Your product did receive BIOS updates - even more recently this year - so it's possible to work, just not as expected (might detected - but won't run at marketed speeds - overheating could also be an issue - due to a design limitation - otherwise they wouldn't include power class requirements in the datasheet, even tho - tech change a lot since then - so maybe not an issue anymore with modern SSDs).

This appears to be a performance classification, not a power classification. This is from a quick search, so I'm not sure.

This Dell link indicates performance:

"M.2 storage devices are classified numerically based on performance. The higher the Class, the faster the overall performance:"

This classification is specific to Dell, and it seems to be true.
Perhaps the 40 and 50 2TB M.2 NVMe 2280 classifications are double-sided, and that might be why your computer doesn't support them. This interferes with installation in the slot.

itsme1 said:

This classification is specific to Dell, and it seems to be true.
Perhaps the 40 and 50 2TB M.2 NVMe 2280 classifications are double-sided, and that might be why your computer doesn't support them. This interferes with installation in the slot.

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Both the Kioxia KXG60ZNV512g and the Samsung 980 pro 500GB are single sided, apparently.

For what it's worth, Kingston also offers 4TB NVME drive upgrades. The 4TB NV3 model is double sided. The 2TB model may be single sided.

bobkn said:

Both the Kioxia KXG60ZNV512g and the Samsung 980 pro 500GB are single sided, apparently.

For what it's worth, Kingston also offers 4TB NVME drive upgrades. The 4TB NV3 model is double sided. The 2TB model may be single sided.

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Don't forget about NVMe 4.0 x4. They've been out for a while now, and I think their price should be equal to or lower than NVMe 3.0 x4.
The Samsung 990 Pro 1 TB, 2 TB et 4 TB PCIe 4.0 x4 are single-sided.
Be careful, this Samsung is sold with a heatsink and without. For a laptop without a heatsink, it's better.