Sandisk extreme portable SSD 2TB - 20% lower than advertised Speed

[Swingman]

I bought a Sandisk extreme portable SSD 2TB read/write speeds of 1050/1000. I was only getting around 800 for both read and write speeds using Black Magic disk checker. I also tried with USB4/ Thunderbolt 4 cable. I was using my Mack book Pro M5. I also noticed that MacBook complaint that I have disconnected without ejecting ( I haven’t and whist connected to Mac).
The original drive is EXFAX and supposed to be formatted to AFPS according to online support chap I contacted. He was giving usual excuses as the speed depends on other bottlenecks, system etc.

Here is his summary email.

 

[Gnits]

I came across a discussion which indicated that max performance is only available through a USB 3.22 port. There is massive small print in relation to disk performance. Also… sustained read or write operations performance usually decay substantially… that is why copying say one disk to another is much slower than expected.

Thunderbolt external SSDs would be a good option for MacBooks… but smaller and more expensive range available.

For LrC type usage LrC does not come close to using the available speeds of ssd drives so getting ultra fast drives can be a poor investment.

Getting a read speed of 863 MB/s is fairly good.

 

[Swingman]

I came across a discussion which indicated that max performance is only available through a USB 3.22 port. There is massive small print in relation to disk performance. Also… sustained read or write operations performance usually decay substantially… that is why copying say one disk to another is much slower than expected.

Thunderbolt external SSDs would be a good option for MacBooks… but smaller and more expensive range available.

For LrC type usage LrC does not come close to using the available speeds of ssd drives so getting ultra fast drives can be a poor investment.

Getting a read speed of 863 MB/s is fairly good.

Matt,
This is a brand new drive and no other data on it. What causes it to disconnect randomly? I have been reading reviews for many brands of external SSD. It appears all of them have similar or worse problems with speed. Many also complained with random disconnection. This imply one needs to have multiple backup plans. That might to ok for corporate users or one with paying clients. For hobbyists it’s getting very expensive considering all external SSD and also HDD have gone up by 50% in 6 month (like gold). We need a pull back.

 

[Gnits]

I have a Samsung T9 external SSDs connected permanently (ie 95% of the time) to my Win machine and it never disconnects. It is my most important disk, holding my catalog, last 2 years images and my personal data files, docs, etc. The other 5% it is connected to my travel M2 MacAir when in my hotel. Mine is formatted as ExFat, as it moved between Windows and Mac machines.

I have seen a few comments re disconnects… so you are not alone. Your MacBook Pro is a very good spec machine. I am steeped in Windows rather than Mac.. hopefully someone with more Mac / disk experience might comment.

I am not sure what you mean by the original drive is Exfax ( I presume ExFat). What is the current format of the drive.

 

[Gnits]

I just found this note re Sandisk disconnects… I did not read the full article.. but I suggest you check the firmware version of your drive.

https://support-en.sandisk.com/app/answers/detailweb/a_id/50818/~/sandisk-extreme-portable-ssd-v2,-sandisk-extreme-pro-portable-ssd-v2,-and-wd-my

“We have identified a firmware issue that can cause some drives to unexpectedly disconnect from a computer.”

 

[Swingman]

I have a Samsung T9 external SSDs connected permanently (ie 95% of the time) to my Win machine and it never disconnects. It is my most important disk, holding my catalog, last 2 years images and my personal data files, docs, etc. The other 5% it is connected to my travel M2 MacAir when in my hotel. Mine is formatted as ExFat, as it moved between Windows and Mac machines.

I have seen a few comments re disconnects… so you are not alone. Your MacBook Pro is a very good spec machine. I am steeped in Windows rather than Mac.. hopefully someone with more Mac / disk experience might comment.

I am not sure what you mean by the original drive is Exfax ( I presume ExFat). What is the current format of the drive.

Matt,
That’s EXFAT. I haven’t changed it. I also have 1TB version of it for some time (6 month). I checked the speed and that also about 800. Your T9 doesn’t give full speed on Macs as I was told it uses 3.2 gen 2x2 and don’t run faster than T7. The Price of T7 &. T9 and lot higher than Sandisk. In paper T7 is similar to Sandisk extreme ssd.

 

[Swingman]

I just found this note re Sandisk disconnects… I did not read the full article.. but I suggest you check the firmware version of your drive.

https://support-en.sandisk.com/app/answers/detailweb/a_id/50818/~/sandisk-extreme-portable-ssd-v2,-sandisk-extreme-pro-portable-ssd-v2,-and-wd-my

“We have identified a firmware issue that can cause some drives to unexpectedly disconnect from a computer.”

Matt,
I had a chat with their support team and they asked for the serial number. They didn’t find any problem. I also checked it on the link and mine does not require one.

 

[Gnits]

Matt,
I had a chat with their support team and they asked for the serial number. They didn’t find any problem. I also checked it on the link and mine does not require one.

ok ... it was worth checking...

BTW... here is the performance test for my Samsung T9. These speeds are way beyond what LrC can cope with .. so I do not worry once they are a few hundred MB/s. I have an M2 Nvme drive in my Win machine which has a rated speed of greater than 6000MB / s ... sitting idle ... as the external T9 works better for my combo of desk and travel use.

I agree .. the disconnect is a more important issue.

 

[Swingman]

I might call Apple tech support and find out anything they could do.

 

[Gnits]

Good idea… Also…is there a system log on Mac which might show system errors…

 

[Conrad Chavez]

The original drive is EXFAX and supposed to be formatted to AFPS according to online support chap I contacted. He was giving usual excuses as the speed depends on other bottlenecks, system etc.

Yes, if you are only going to use the SSD with Apple devices, do not make a final judgment about speed until the drive is reformatted as APFS.

APFS (Apple File System) is definitely recommended for any SSD that will be used only with macOS/iOS devices. APFS is supposed to be faster than ExFAT; in other words, on a Mac it is totally expected that ExFAT SSD transfer speed will be slower than with APFS. Also, APFS supports the latest Apple storage features such as FileVault encryption, journaling (for better error recovery), cloning (to save space when duplicating files on the same volume), and SSD-specific performance optimizations. It is also said that APFS is less prone to corruption than ExFAT.

The only reason to use ExFAT for an SSD connected to a Mac is if you also need it to work when plugged into non-Apple devices such as Windows PCs.

The reason everybody ships new drives as ExFAT is convenience: The drive company knows that a customer can plug an ExFAT drive into a device running the most popular OSs and it will be usable right away. But for any user who insists on the highest possible performance or full feature compatibility, it’s usually better to reformat an SSD for APFS (macOS), NTFS (Windows), or whatever works best for purpose.

(That’s only about speed, the volume format probably has nothing to do with the unexpected disconnections. I don’t know why that’s happening. I have seen unexpected disconnections in the past, but currently the connections have been stable to the SSDs currently used daily with my Mac.)

 

[Conrad Chavez]

I came across a discussion which indicated that max performance is only available through a USB 3.22 port. There is massive small print in relation to disk performance. Also… sustained read or write operations performance usually decay substantially… that is why copying say one disk to another is much slower than expected.

I think that discussion was about USB 3.2 Gen 2x2 (yes, a terrible naming convention) which is rated at 20Gb/sec (around 2000MB/sec real world), but no Mac supports USB 3.2 Gen 2x2 and very few PCs do. On most computers, a USB 3.2 Gen 2x2 drive runs at only 10Gb/sec.

If their Sandisk Extreme SSD is rated as 10Gb/sec USB (roughly 1000MB/sec), the tested speed on a Mac or PC that supports USB 3.2 @10Gb/sec should be in the range of 900–1000+MB/sec…which is achievable if:

• (for Macs) The drive is formatted as APFS
• The cable and any hubs in between are also rated for at least 10Gb/sec, and are of high quality with no defects
• The files are large (small files involve more overhead so the reported transfer rate is much lower)
• The USB controller is not too busy with other USB devices on the same bus, such as other SSDs, external displays, etc.

I agree with you that given all of that, over 800MB/sec is pretty good in real world use.

 

[Swingman]

I think that discussion was about USB 3.2 Gen 2x2 (yes, a terrible naming convention) which is rated at 20Gb/sec (around 2000MB/sec real world), but no Mac supports USB 3.2 Gen 2x2 and very few PCs do. On most computers, a USB 3.2 Gen 2x2 drive runs at only 10Gb/sec.

If their Sandisk Extreme SSD is rated as 10Gb/sec USB (roughly 1000MB/sec), the tested speed on a Mac or PC that supports USB 3.2 @10Gb/sec should be in the range of 900–1000+MB/sec…which is achievable if:

• (for Macs) The drive is formatted as APFS
• The cable and any hubs in between are also rated for at least 10Gb/sec, and are of high quality with no defects
• The files are large (small files involve more overhead so the reported transfer rate is much lower)
• The USB controller is not too busy with other USB devices on the same bus, such as other SSDs, external displays, etc.

I agree with you that given all of that, over 800MB/sec is pretty good in real world use.

Excuse my spelling mistakes.
I also have a similar SDD with 1TB advertised speed of 1050/100. I have reformatted that drive to APFS but the speed remains at around 850/800. No significant difference. I deliberately avoided 3.2 gen 2.2 due to no real advantage for use with Mac. Now I am using it for TM backup until I get a large HDD for it.
I also tested the 2TB with new Thunderbolt 4/ USB4 cable rated 40Gb/s, but the speed didn’t improve. I had online chat with Sandisk technician support, he suggested that other external factors may be affecting the speed (usual excuse, not not our product’s fault). So asked what is the internal interface is. He said 3.2 gen 2. And capable of 10Gb/s.
I also read reviews in Amazon for other manufacturers products and generally a large percentage complained about speed and also said get slower during large transfers and disk slow down significantly when they get to 80 to 90% full.

 

[Gnits]

and also said get slower during large transfers and disk slow down significantly when they get to 80 to 90% full.

I do not like this… but that seems to be the nature of the architecture. My assumption is that various caches fill up for the larger copy jobs… on the drive itself and caches used by the o/s.

This is not just a factor for ssd’s but also for hdd drives. I was horrified how slow it was to copy 5 TB drives (drive a to empty drive b).. both with internal Sata connections.

This is probably a reason raid is still a solution for some people who need super sustained disk I/o.

 

[Swingman]

I do not like this… but that seems to be the nature of the architecture. My assumption is that various caches fill up for the larger copy jobs… on the drive itself and caches used by the o/s.

This is not just a factor for ssd’s but also for hdd drives. I was horrified how slow it was to copy 5 TB drives (drive a to empty drive b).. both with internal Sata connections.

This is probably a reason raid is still a solution for some people who need super sustained disk I/o.

Matt, I never had this problem when using 51/4” single sided floppy on Commodore console’s external disk drives!

 

[Conrad Chavez]

I also read reviews in Amazon for other manufacturers products and generally a large percentage complained about speed and also said get slower during large transfers and disk slow down significantly when they get to 80 to 90% full.

Yes, there are a lot of variables. During large transfers, SSDs can slow for at least two reasons other than getting full.

Cache size is one reason. An SSD with a larger cache can sustain faster transfers for longer, but those cost more.

Another reason is heat. An SSD that reaches maximum temperature will slow itself down to prevent overheating. It might not be a problem for small occasional writes where the SSD can cool off between transfers, but the longer or more frequent the transfer the more chance it will reach maximum temperature and throttle down. This is becoming a much bigger problem with faster protocols like USB 4 and Thunderbolt 4 and 5, where the speeds are so high (3000–6000+MB/sec) that the SSD heats up a lot faster. This is why external SSDs that run that fast are often found in larger metal enclosures with cooling fins. There are even some sold now with tiny fans in them.

So, if you get a cheap SSD with a small cache and not much cooling, it’s likely to perform very fast for a short time, and then after a while you might see two different kinds of slowdown as the cache fills up and max temperature is reached. Unfortunately, with the recent price increases, even the mediocre SSDs are not as affordable.