Lab-tested storage, starting with memory cards

CKBench is the bench we built because the numbers on the package answer almost none of the questions that matter. Every test byte is committed to the device and confirmed, every byte is read back and checked, and the result gets published whether it flatters the product or not. Its first module is CardCheck, for memory cards, and a microSD is a good place to start: it is the cheapest component in your dash cam and the one most likely to quietly ruin it.

CardCheck · the corpus

Memory cards: every one we have tested

Same bench, same reader, same suite, with one exception the table states outright: a microSD Express card carries PCIe on its second row of pins and cannot reach that bus through any ordinary reader, so it was run on both and appears twice, once per bus. Every other row shares one measurement chain. Write speed is committed sequential, which reads lower than burst benchmarks because every byte had to land before the clock stopped. Capacity is what the card actually delivered against the number on its label, verified byte by byte.

Card	Committed write	Sustained floor	Capacity delivered	Peak temp	Score
SanDisk High Endurance 128GB	89.7 MB/s	88.0 MB/s, V60	100.0% of label	151.4 F	5/5
Kioxia Exceria G2 128GB	65.3 MB/s	62.6 MB/s, V60	96.7% of label	143.3 F	4.5/5
VIOFO High Endurance 128GB	57.0 MB/s	55.8 MB/s, V30	97.4% of label	160.8 F	3/5
VIOFO High Endurance 32GB	35.2 MB/s	14.9 MB/s, V10	99.1% of label	152.9 F	3/5
ProGrade SDXC UHS-II V60 128GB	108.4 MB/s	102.8 MB/s, V90	100.1% of label	145.1 F	4/5
Lexar Professional 1667x 128GB	119.3 MB/s	109.5 MB/s, V90	100.0% of label	142.7 F	4.5/5
Samsung PRO Ultimate SD 512GB	137.3 MB/s	133.1 MB/s, V90 on this reader V60 in a camera	100.1% of label	144.4 F	4.5/5
Samsung P9 Express 256GB (SD Express)	212.9 MB/s	161.3 MB/s, V90	100.1% of label	194.8 F	4/5
Samsung P9 Express 256GB (UHS-I fallback)	87.7 MB/s	87.0 MB/s, V60	100.1% of label	140.9 F	4/5
Samsung PRO Plus 512GB	142.2 MB/s	141.6 MB/s, V90	100.1% of label	169.6 F	4.5/5
Botslab 128GB (bundled)	59.0 MB/s	53.9 MB/s, V30	97.4% of label	135 F	3/5
FitcamX 64GB (bundled)	47.1 MB/s	43.8 MB/s, V30	97.3% of label	131 F	4/5
Newegg TeamGroup 128GB	39.8 MB/s	35.5 MB/s, V30	96.7% of label	133 F	2.5/5
SanDisk ImageMate 128GB	33.2 MB/s	31.8 MB/s, V30	26.8% of label	150.1 F	1/5
SanDisk Extreme 512GB	135.8 MB/s	127.6 MB/s, V90	100.0% of label	172.3 F	4.5/5
Lexar Silver Plus 128GB	157.0 MB/s	153.4 MB/s, V90	98.8% of label	158.0 F	4.5/5
Samsung EVO Plus 128GB	82.0 MB/s	83.6 MB/s, V60	100.0% of label	135.0 F	5/5
SanDisk Ultra 128GB	60.7 MB/s	59.7 MB/s, V30	99.9% of label	155.0 F	4.5/5
Lexar Blue 128GB	152.6 MB/s	155.1 MB/s, V90	98.2% of label	162.0 F	4.5/5

The VIOFO 32GB's sustained floor is duty-dependent and is shown here on the same measurement every other card gets. Under pure video recording it holds 34.2 MB/s and its V30 rating; the 14.9 figure is what it does for about 75 seconds after a burst of random small writes. The review explains which number applies to you.

What the table shows

Six patterns across fifteen cards

Fifteen cards, one measurement chain. Read down the columns and the same shapes keep coming back, and not one of them is visible from a single review.

1 of 15

was not the size on its label. The SanDisk ImageMate holds 34.3 GB behind a 128 GB label while passing Class 10, U3, A1 and V30. Every other card delivered between 96.7% and 100.1%.

9 of 13

cards that print a video speed class sustain a higher one, every one of them by at least a full class. The PRO Ultimate, the PRO Plus, the P9 Express, the SanDisk Extreme and the Lexar Silver Plus beat theirs by two, holding V90 against a printed V30. Only the VIOFO 32GB falls below its mark, and only for about 75 seconds after random writes.

3 of 11

cards that print a write speed miss it by a margin that matters: the VIOFO 128GB by 29%, the Newegg TeamGroup by 20%, the ProGrade by 17%. It runs the other way more often. Seven of the eleven beat their claim, the SanDisk High Endurance most of all at 89.7 MB/s against a printed 40.

3 of 15

never write at one steady speed. The Botslab cycles between 34 and 82 MB/s every 9.5 seconds, the TeamGroup between 5 and 83 every 2.7, and the FitcamX runs a 2.13 second rhythm that makes an honest card look broken. Neither of the two that print a V30 ever drops below it.

2 of 15

change what they are depending on the reader. The P9 Express carries PCIe on its second row of pins: 89.7 MB/s read on an ordinary reader, 596.7 on an Express one. The PRO Ultimate holds V90 on a reader that speaks Samsung's fast mode, V60 on the plain bus a camera gives it. Which reader to buy is its own question.

1 name

covers two different cards. The VIOFO High Endurance 32GB and 128GB share a brand, a package and a product line, and their identity registers name two different manufacturers seventeen months apart.

CardCheck · the distribution

Where each card sits against the rest

A review can tell you a card held 88.0 MB/s. It cannot tell you whether that is good. Every ranking below is computed at build time from the same results files the table above prints, across eighteen cards and nineteen measured rows, and it is worth being blunt about what that makes it: these are percentiles of our bench, not of the market. We have tested these cards. We have not tested the ones we have never held, so n is printed beside every ranking on the page and you can weigh it yourself.

The rows are grouped by host bus and ranked only against their own group. Of the three buses represented here, UHS-I is the only one carrying enough cards (sixteen) to support a ranking at all. Any bus below that line is listed with its measurements and no percentile, and earns one once it reaches eight cards.

UHS-I16 cards

Card	Label	Worst-10s sustained write	Committed sequential write	Peak temperature
Lexar Blue 128GB	128 GB	155.1 MB/sfastest of 16p97	152.6 MB/s2nd fastest of 16p91	162.0 F14th coolest of 16p16
Lexar Silver Plus 128GB	128 GB	153.4 MB/s2nd fastest of 16p91	157.0 MB/sfastest of 16p97	158.0 F12th coolest of 16p28
Samsung PRO Plus 512GB	512 GB	141.6 MB/s3rd fastest of 16p84	142.2 MB/s3rd fastest of 16p84	169.6 F15th coolest of 16p9
Samsung PRO Ultimate SD 512GB	512 GB	133.1 MB/s4th fastest of 16p78	137.3 MB/s4th fastest of 16p78	144.4 F7th coolest of 16p59
SanDisk Extreme 512GB	512 GB	127.6 MB/s5th fastest of 16p72	135.8 MB/s5th fastest of 16p72	172.3 F16th coolest of 16p3
SanDisk High Endurance 128GB	128 GB	88.0 MB/s6th fastest of 16p66	89.7 MB/s6th fastest of 16p66	151.4 F9th coolest of 16p47
Samsung P9 Express 256GB (UHS-I fallback)	256 GB	87.0 MB/s7th fastest of 16p59	87.7 MB/s7th fastest of 16p59	140.9 F5th coolest of 16p72
Samsung EVO Plus 128GB	128 GB	83.6 MB/s8th fastest of 16p53	82.0 MB/s8th fastest of 16p53	135.0 F3rd coolest of 16p81
Kioxia Exceria G2 128GB	128 GB	62.6 MB/s9th fastest of 16p47	65.3 MB/s9th fastest of 16p47	143.3 F6th coolest of 16p66
SanDisk Ultra 128GB	128 GB	59.7 MB/s10th fastest of 16p41	60.7 MB/s10th fastest of 16p41	155.0 F11th coolest of 16p34
VIOFO High Endurance 128GB	128 GB	55.8 MB/s11th fastest of 16p34	57.0 MB/s12th fastest of 16p28	160.8 F13th coolest of 16p22
Botslab 128GB (bundled)	128 GB	53.9 MB/s12th fastest of 16p28	59.0 MB/s11th fastest of 16p34	135 F3rd coolest of 16p81
FitcamX 64GB (bundled)	64 GB	43.8 MB/s13th fastest of 16p22	47.1 MB/s13th fastest of 16p22	131 Fcoolest of 16p97
Newegg TeamGroup 128GB	128 GB	35.5 MB/s14th fastest of 16p16	39.8 MB/s14th fastest of 16p16	133 F2nd coolest of 16p91
SanDisk ImageMate 128GB	128 GB	31.8 MB/s15th fastest of 16p9	33.2 MB/s16th fastest of 16p3	150.1 F8th coolest of 16p53
VIOFO High Endurance 32GB	32 GB	14.9 MB/s16th fastest of 16p3	35.2 MB/s15th fastest of 16p9	152.9 F10th coolest of 16p41

UHS-II2 cards

Two rows are not a distribution, so nothing on this bus is ranked. These are the measured figures, for reference. This bus earns percentiles at eight cards.

Card	Label	Worst-10s sustained write	Committed sequential write	Peak temperature
Lexar Professional 1667x 128GB	128 GB	109.5 MB/s	119.3 MB/s	142.7 F
ProGrade SDXC UHS-II V60 128GB	128 GB	102.8 MB/s	108.4 MB/s	145.1 F

SD Express1 card

One row is not a distribution, so nothing on this bus is ranked. This is the measured figure, for reference. This bus earns percentiles at eight cards.

Card	Label	Worst-10s sustained write	Committed sequential write	Peak temperature
Samsung P9 Express 256GB (SD Express)	256 GB	161.3 MB/s	212.9 MB/s	194.8 F

Six things these percentiles are not

Not the market. We have run eighteen cards across this bench. A percentile here places a card among those and says nothing about the thousands we have never touched. Treat it as context for a number, never as a market share of quality.
Not one ladder. A UHS-II card and a UHS-I card are not competing for the same job, and ranking them together would hand the faster bus a placing it earned from its pinout rather than from its silicon. Each bus is scored only against itself, which is also why one card measured on two buses appears in two groups.
Not independent of capacity. Within UHS-I, label capacity and sustained write correlate at +0.61. Sustained write scales with the dies a card has to interleave, so a small card ranks low here partly for physics rather than for quality. The label sits in the table for exactly that reason.
Not a heat verdict. Peak temperature and sustained write correlate at +0.54 on this corpus: the quickest cards run the hottest, so the coolest card on the bench is frequently just the slowest one. That column is ranked so you can see the position, and its bar is left deliberately colourless so it cannot read as praise.
Not two opinions on write speed. The two write columns rank the same cards in almost the same order, at a rank correlation of 0.99. Read them as one finding measured two ways, not as two sources agreeing with each other.
Not a score. Scoring stays rubric-based and category-relative: a card is judged against the job it is sold for. A dash cam card that clears its camera's real duty many times over does not lose points for sitting low on a ladder built mostly of cards sold for harder work.

These are the same figures the corpus table prints, so any caveat attached to a number up there travels with its ranking down here, including the duty-dependent floor footnoted beneath the table.

The card that under-sells itself. It committed writes at 89.7 MB/s against a printed 40, held V60 against a printed V30, delivered all 128.0 GB with zero mismatched bytes…

Read the deep dive

Beyond cards

The bench tests its own gear too

CKBench is not only for review samples. Before a piece of storage earns a job on this bench, it gets the same suite as everything else, and the first one through was a USB flash drive about to become the boot device for our card-identity rig. It is not a memory card, so it is scored on its own terms and stays out of the card table above. It also produced the strangest finding on this page: a drive whose read speed depends on how the data on it was written.

Scored 4/5 as a flash drive

SanDisk Ultra Fit 32GB

The thumb drive that beat its only printed number and hid everything else. 148.8 MB/s read against a claimed 130, full capacity verified with zero bad bytes…

Read the bench notes

Start here

What buyers actually ask

Should I replace the card that came with my dash cam? Probably not, and we have now tested four of them. The bundled Kioxia beat its own spec and handled loop recording without flinching, and the Lexar Silver Plus that replaced it in the next camera outwrites every card on this bench, retail ones included.

How do I tell if my card is fake? Not with a benchmark. Check the reported size first, then fill the whole card with verifiable data and read it all back. The counterfeit we tested passes every speed test there is.

Why does my 128GB card only show 119 GB? That is normal. Your computer counts in binary, so 128,000,000,000 bytes displays as about 119 GB. Nothing was taken. A real shortfall looks very different, and the Kioxia review explains where the missing gigabytes on that card actually went.

Do I need a special card for a Nintendo Switch 2? Yes, it needs microSD Express, and the marking to look for is EX. An ordinary microSD will not run games on it, and a UHS-II card will not either: both rows of pins look alike but carry different signals. We tested one on two readers to show what the format actually delivers.

Which of these should I actually buy? Answer three questions in the card finder and it names one or two. If you would rather see the working, the full card picker takes a specific camera and lays every measurement out side by side against it.

How much footage fits on a card? Work it out for your own camera's bitrate in the dash cam storage calculator.

Do you only test memory cards? No. Anything storage can go on the bench, and the gear we rely on ourselves goes on first. The SanDisk Ultra Fit 32GB got the full suite before we trusted it to boot our card-identity rig.

The method

How these numbers are produced

Every figure on this page comes from one results file per card, written by a bench built for this: writes are committed and confirmed before the timer stops, a cache-leak canary aborts the run if the operating system serves a cached read, and every test byte is seeded so it can be verified on the way back. Cards are scored on five dimensions against the job they are sold for, and a card that misrepresents its capacity is capped at 1 out of 5 no matter how fast it is.

The full method, the rubric, the unit conventions and an honest list of what we deliberately do not test are all on one page. Alongside it sits the reference we built while identifying these cards: every SD manufacturer ID we have decoded, and an honest account of what that number can and cannot prove.

How we test and score memory cards

The bench, the five-dimension rubric, the conventions, and the gaps we will not paper over.

Read the method

SD card manufacturer IDs, decoded

Look up the CID register your own card reports, and see why a matching manufacturer ID does not make a card genuine.

Read the register