microSD card really slow write speeds

[gwynbleidd997]

SOLVED:

Uncheck the "Quick Format" box and format it. If you're on linux or something, look for a formatting option that will zero the whole card out (writes zeros to the whole thing). It will take hours to finish depending on the capacity and write speeds you're getting. Best just leave it overnight.
I also had a 32MB unallocated space in the front (before the main partition) that I got rid of. I don't know if that helped or made things worse, but I wouldn't touch it.
After slow formatting it (I used NTFS again, I doubt it matters though if it's NTFS or exFAT), the speeds are back to normal. I think I used 8KB allocation size instead of the default 4KB. Not sure if that helped.
I have no idea why or what happened exactly, but it works fine now. Maybe someone with more knowledge can tell us what's up.

Ubuntu ISO, around 5GB, copies perfectly fine now at a constant speed.

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Hi,

I've had this samsung pro plus 256GB microSD card (MB-MD256KA/EU) for almost a year now. I wasn't using it all that often but recently I noticed the (sequential) write speeds are really really slow.
Like 4-5MB/s type of slow.

I'm using my laptop's built-in card reader for it, and I tested another microSD card a while back and saved the results (around 17MB/s writes). This samsung one should at least be as fast as the other one, if the card reader was the limiting factor (it probably isn't).
The laptop is relatively new, a zenbook 14 flip OLED with a 5900HX. The same model but with a 5800H tested on notebookcheck was doing around 90MB/s read speeds from their tests, so the card reader is capable of those speeds (I assume if it can read from a card at that speed, it can also write to it at the same speed).
The samsung microSD card has the U3 and V30 ratings, so it should do 30MB/s (write) minimum with a constant load. As you can see above, it can only do about 5.

The card was bought on amazon and was sold directly by amazon, so it's most likely genuine as it was sealed. It's virtually impossible to open up the kinds of packages these cards come in and reseal them back up. I have no doubts that it is genuine.

I tried NTFS, exFAT, let it cool off a bit... nothing seems to be helping.
Is it broken? what is happening here?

Appreciate any input.

 

[SPDIF]

Most likely your card reader is internally connected to an USB 1.1 or USB 2.0 input. Only on USB 3.0 you would get high rates on reading and writing.

 

[ty_ger]

Well, you did say that you are using the laptop's built in card reader. Maybe that is by design.
just kidding
But it could be a bus design issue.

 

[SPDIF]

On almost all laptops the card reader is internally connected to the USB bus. So if they use an older USB connection it will be slow. I think it will be a lot faster with an external and REAl USB 3.0 reader. That is, if your laptop has USB 3.0 connections. The first USB 3.0 devices build-in where very very slow and had a lot of problems with driver and firmware issues.

 

[Wirko]

Computer interfaces and associated communication protocols are equally fast in both directions. 85 MB/s is above USB 2.0 speed, therefore the interface is not USB 1.1 or 2.0 but something faster.

 

[SPDIF]

That 85MB reading is probably due to internal cache. You only can find out the culprit if you have a good and fast external USB 3.0 reader to test this out. I am quite sure you would get very high speeds.

This is one of the fastest USB 3.0 readers i ever tested and sold here.

But that writing is really ridiculous low speed. Could also be a driver problem or just a slow internally build-in read/write card. As said you only can find out if you test it with a REAL USB 3.0 external connection.

 

[Wirko]

That 85MB reading is probably due to internal cache.

That's possible but the effect of cache is easy to exclude. Reboot, re-insert the card, read large files. If the average speed remains above USB 2.0 top speed then I wouldn't suspect a slow interface; however, the card reader might still be a poor card writer, or might have a failure.

 

[sam_86314]

It's definitely related to the caching on the card. I've encountered similar scenarios when copying hundreds of gigs to a microSD card.

In the case of SSDs, they'll usually run a portion of the NAND in SLC mode, which improves performance. After that cache is used up, it'll drop down to whatever the NAND natively runs as, which will be slower.

MicroSD cards probably use lower-grade TLC or QLC NAND, so once any write cache is used up, they'll drop really low.

In the case of my 400GB SanDisk Extreme, it starts around 100MB/s, then after probably 50GB, it alternates between 5MB/s and 30MB/s until all data is written.

 

[Wirko]

The samsung microSD card has the U3 and V30 ratings, so it should do 30MB/s (write) minimum with a constant load. As you can see above, it can only do about 5.

If you happen to have a camera that can record video, or a series of photos, with a data rate faster than 5 MB/s, you can use it for testing. Cameras have write caches for continuous photo shooting though, and you'd have to take that into account.

 

[SPDIF]

The build-in card readers are most of time cheap/low quality, so never expect top speeds with that in a laptop. There are fast laptops with fast readers, but that you see reflected in a high price to pay.

Also another USB device connected to the same bus internally could influence the speed. WiFi is most of time also connected to the USB bus. But that write speed is really abnormal.

 

[gwynbleidd997]

Thanks for the replies. I can confirm it has nothing to do with the laptop's microSD slot, reader, controller... whatever it is.
I have a sandisk extreme 128GB U3 V30 used in my galaxy S9+ that I just tested and it's perfectly normal, after like 4 or 5 years of use:

So it's the sd card then, nothing to do with the laptop.
Anyone has any idea what's wrong with it?

 

[Shrek]

Most likely your card reader is internally connected to an USB 1.1 or USB 2.0 input. Only on USB 3.0 you would get high rates on reading and writing.

The bus can handle 85, so that would not explain the 5

 

[SPDIF]

Would be interesting to test out that memory card. I think the answer from sam above here should make sense. But indeed that write speed is really abnormal.

And on another computer you said it works okay? The only thing i can imagine that makes sense is that there is maybe some incompatibility problem between card en reader.

 

[Tahagomizer]

That's microSD cards for ya. All the new ones are monolithic dies built with the lowest quality NAND, usually leftovers form more lucrative businesses like SSD/EMMC. Probably the flash degraded to a point at which the controller can't handle CRC errors fast enough, or it has a dead channel, likely both. Best to write it off and remember to never store important data without a reliable backup. This is true for any medium, not just cheap, trashy flash memory.

 

[gwynbleidd997]

Would be interesting to test out that memory card. I think the answer from sam above here should make sense. But indeed that write speed is really abnormal.

And on another computer you said it works okay? The only thing i can imagine that makes sense is that there is maybe some incompatibility problem between card en reader.

Problem solved, go to the first post.
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Here's something even more peculiar; I left the sd card formatting (not a quick format) and kept periodically checking the speeds in task manager. I saw it jump up to around 30MB/s and also go down to 7MB/s. The formatting takes a long time since it has to zero the whole card and it's 256GB with those speeds.

Right now it's at 13MB/s at around 90% done:

Is this the "faster" cache? is only a small portion of the cells actually capable of the V30 speeds? how come do people benchmark this sd card and get like 80-something MB/s write speeds when they first get it? if that's the cache, why isn't it working here as well? I left the sd card plugged in, completely empty and doing nothing for at least an hour last night and went back to it and tested it again, same abysmal speeds copying a big file over, so it's not filled up cache.

That's microSD cards for ya. All the new ones are monolithic dies built with the lowest quality NAND, usually leftovers form more lucrative businesses like SSD/EMMC. Probably the flash degraded to a point at which the controller can't handle CRC errors fast enough, or it has a dead channel, likely both. Best to write it off and remember to never store important data without a reliable backup. This is true for any medium, not just cheap, trashy flash memory.

Until recently I wasn't really using it all that much. It's one year old and didn't see much use unlike the one currently in my phone that's been there for 4-5 years, going through many more write cycles than this samsung one.

Wtf...

 

[SPDIF]

That's normal, if you do a fast format data is not really deleted, it just marks the data as abandoned. But it stays on you sd-card and your card does not know you deleted this. So data stays going around in the NAND and make it very slow, just the same as a SSD for PC.

 

[Wirko]

I

That's normal, if you do a fast format data is not really deleted, it just marks the data as abandoned. But it stays on you sd-card and your card does not know you deleted this. So data stays going around in the NAND and make it very slow, just the same as a SSD for PC.

Is TRIM possible on SD cards and USB flash drives? A quick web search doesn't give me a clear yes or no, but rather a maybe (only on some cards/only manual trim/after additional setup in Windows, etc.)