Micro SD cards for things like Raspberry Pi

OK - rebuilt my RPi4 8 GB model with Raspbian arm64 and XFCE 4…

Not 100% happy with it… it seemed more responsive previously…

The main difference being, when I tried re-formatting the original 64 GB SD Card I was using before - I ran into issues, so I thought, “hmmm, because my plan is to put a bigger card in there anyway, so creating a “gold” image of a 16 GB card is going to be easier than a 64” - so I built it on a 16 GB.

Both cards (the 16 and 64) are SanDisk Ultra… Could my anecdotal “slowness” be down to the card? The 16 GB card is considerably older than the 64 (by 2-3 years?)…

I read some online stuff recently, and from what I’ve read, Samsung Evo Plus/+ cards are supposedly “better” than Sandisk - so I ordered 2 x 256 GB cards from e-bay, but was considering ducking out and grabbing a 128 GB Samsung card while I’m waiting (can never have too many of these)…

Just wondering if someone like @Akito has any recommendations?

Mainstream dictates what is being produced in masses.

Mainstream uses videos, photos and audio files, which are usually relatively large (up to tens of GB for video files and I have whole single-file music albums which also span GBs), so the flash card standard absolutely focuses on reading and writing (mainly reading) large files as quickly as possible.
That, in turn, means that reading a large number of small files (like for a program, for an OS, for other data files for anything that is not belonging to one of the categories mentioned above) is comparatively extremely slow. My Samsung EVO 970 Pro M.2 SSD that can have read speeds of several thousand MB/s, is still comparatively slow, when moving lots of tiny files.
Same with SD cards. Almost all SD cards are Class 10 or even U1 and U2. These classes promise higher speeds, however the higher the class, the more it specializes on few large files, instead of huge amounts of tiny files. So yes, the speed is higher, but not for tiny files.
This is the main reason, I read on the internet some day, that Class 4 (supposedly slow SD cards) could be actually faster for a Raspberry Pi, because the technology does not specialize on large files as much as e.g. Class 10 does.
Since bigger SD cards expect these big files even more obviously, they are, as far as I have seen, even more on the large files trip, so it is even less likely to get support for fine r/w speeds for small files, as these cards are usually used for huge files (like RAW photos in a DSLR).

That could be a common cause for what you experienced.

But could also be related to another reason, like as to how the OS supports and deals with larger SD cards. For example, you cannot use hard disks larger than 2TB on Windows XP. I could imagine there could be some limitation or quirk in this situation too, however that is speculation, only.

I guess, the best solution to find out what’s going on in this specific case is by gathering numbers and facts, so we don’t have to speculate anymore.

did a quick google-fu, and someone here : https://ccollins.wordpress.com/2016/01/18/testing-sd-cards-with-linux/ suggested using “disks” util that comes stock with gnome distros (like ubuntu)…
i.e. hit super key and type disks, and there’s a benchmarking tool!!!
Just graphing a circa 2018 64 GB Sandisk “Ultra” VS an 2015/16 16 GB Sandisk “Ultra”… and the bigger one is wiping the floor with the smaller one…
That would explain the “anecdotal” lag I’m getting with my current build of RaspbiOS arm64 on a 16 GB micro SD card.
At some stage, I want to cutover to having just the bootloader watchamacallit on SD card, but boot the rest from faster USB3 storage…

16 GB “Ultra” :


64 GB “Ultra” :

128 GB “Ultra” :

(which I was using for elementary arm64 on RPi4 4GB model)

I think what they’re saying, the bigger (and newer) cards are capable of higher write speeds (but the troughs indicate they can drop lower than the smaller capacity cards)…

Bear in mind - I’m aware there’s an “industry” of fake cards on e-bay and such, and I think I might have bought all my 16 GB cards off e-bay (for my shitty Pine64 boards) - so it’s entirely possible the 16 GB cards I have are not really “Ultra”… Don’t remember where I got this specific 64 GB card from, could have been e-bay, could have been something like OfficeWorks (stationery and office supply retail chain stores).

I’m hoping to see something higher when my Samsungs arrive, as the Samsung Evo Plus/+ are rated at 100 Mb/s read…

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Tom’s Hardware just did a review of the best SD cards for Raspberry Pi’s
https://www.tomshardware.com/best-picks/raspberry-pi-microsd-cards

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Good finding indeed.

This article clears some things up. I didn’t even know about the A category class.

However, I kind of miss the brand I am almost exclusively using for pretty much any device using microSD cards: Transcend. I use this brand since many years and am pretty satisfied with it. I experienced some failed cards with this brand too, but the failure rate was still by far lower than any other brand I ever tried.

  • Kingston -> big fail
  • SanDisk -> big fail
  • Noname -> big fail
  • Intenso -> OK, but still worse than Transcend