Class 6 vs Class 10 : Benchmarking SDHC Cards

T

TheDingo

Veteran
A friend lent me a new Patriot LX Class 10 card to test against the new Patriot IRIS Class 6 card that I bought a few weeks ago. Benchmarking the two cards, I was a little surprised to see how close their performance is.

Patriot 32GB IRIS Class 6 Card
Patriot32GBIRISClass6.jpg


Patriot 16GB LX Class 10 Card
Patriot16GBLXClass10.jpg


...So the Class 10 card is able to write at almost 19 MB/sec ( 152 Mb/sec ), while the class 6 card is able to write at 17 MB/sec ( 136 Mb/sec ). Both of these cards read at 20 MB/sec ( 160 Mb/sec ).

Either of these cards is a total speed demon for the HMC150 camera. ( though I think I will keep buying IRIS cards for the 5 year warranty )
 
Realise that some of this will be governed by the reader you are using as well as the card itself. Class 10 cards could be faster on another reader.
 
Exact said:
Realise that some of this will be governed by the reader you are using as well as the card itself. Class 10 cards could be faster on another reader.
Click to expand...

I've benchmarked about 30 SD cards now ( 7 different brands ), and I've found almost no difference between card readers when running these benchmarking tests.

The SD reader I've been using for the past year is the compact Transcend P5 reader, which looks almost like a small pack of gum.

Transcend P5 Compact USB Card Reader

CardReaderP5_360X310.jpg
 
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I think that the main reason why these two different card classes benchmark so closely is that the speed of the actual chips used to build these cards are almost equivalent. Patriot is a memory manufacturer, that's pretty much their only business, so it appears that they are using premium quality chips in their cards.

A Class 6 card has to be able to maintain a minimum write/read speed of 6 MB/sec ( 48 Mb/sec ), while a Class 10 card has a minimum write/read speed of 10 MB/sec ( 80 Mb/sec ), so both of the Patriot cards that I benchmarked are way over the minimum spec for the classes.

...If anyone would like to test their own SDHC cards, you can download the ATTO disk benchmark software for free at this link:

Free ATTO Disk Benchmark Software ( Windows )
http://www.attotech.com/products/product.php?sku=Disk_Benchmark
 
What benefits would I see in real life from faster cards like those two comparing to another class 6 card that performs at the minimum of the class specs? Would the only benefit be in faster transfer to a computer/harddrive?
Shooting on GH1 and HMC150.

My other question is: comparing 16 & 32GB cards of the same brand (let's say Patriot Iris) would the write/read speeds be the same (or close to same)?
 
Xaveryptak said:
What benefits would I see in real life from faster cards like those two comparing to another class 6 card that performs at the minimum of the class specs?
Click to expand...

My guess the main benefits would be:

1- Faster transfer speed

2- Some degree of future-proofing ( i.e. The camera you buy 2 years from now requires memory that can handle 12MB/sec writes, so these Class 6 cards will still work )

3- Perhaps reliability ( memory will always be able to surpass minimum spec of the camera )

Xaveryptak said:
My other question is: comparing 16 & 32GB cards of the same brand (let's say Patriot Iris) would the write/read speeds be the same (or close to same)?
Click to expand...

Assuming the manufacturer is using similar chips to make both cards, then the speed should be identical.

I own 4 Patriot "Blue" 16GB Class 6 SDHC cards and 2 Patriot "Blue" 8GB Class 6 cards that I bought last summer. All 6 cards have a write speed of 13GB/sec and a read speed of 20MB/sec, and to date I've never had any errors from these cards.

I plan on slowly replacing everything with Patriot 32GB IRIS cards because I like having 3 hours of HD capacity from each card. Price wise they are competitive with the other brands.
 
Cranky said:
Most current readers are limited to 20 MB/s: http://www.tomshardware.com/reviews/sdhc-memory-card,2143-10.html

"Read transfer performance is limited by the card reader’s performance, but write performance is much more interesting." -- In their case write performance differed widely, in your case write performance hits the reader limitation.
Click to expand...

...This is probably why the read performance uniformly stops at 20MB/sec when I benchmark fast SDHC cards.

As far as the write speed goes, if one card can write at almost 19MB/sec and the other writes at 17MB/sec, I sincerely doubt that the slower card is being limited by the reader's hardware, but rather is an indication of the speed limit of the actual chips used in the memory card.
 
TheDingo said:
As far as the write speed goes, if one card can write at almost 19MB/sec and the other writes at 17MB/sec, I sincerely doubt that the slower card is being limited by the reader's hardware, but rather is an indication of the speed limit of the actual chips used in the memory card.
Click to expand...
Right. But if a card writes at 19 MB/s and a known interface limitation is around 20 MB/s then you cannot be sure whether the card hit its own limit or the reader's limit. It is questionable whether you need cards with higher performance anyway: the camera does not need it, and the reader cannot chew it.
 
Cranky said:
It is questionable whether you need cards with higher performance anyway: the camera does not need it, and the reader cannot chew it.
Click to expand...

Buying higher performance memory rarely causes a problem. Problems almost always occur from memory that is either too slow, or out of the original design spec.

...It would be nice to know if there are any SD card readers that do not have this artificial 20 MB/sec speed limit. Or do you think there is some technical reason for having this limit?
 
There is some Sandisk readers that go up to 30MB/s max like this one.

I have one and it's much faster. I am testing my cards right now and I got this result with my Panasonic 16 GB Class 6:
Maximum result
Write: 30161 MB/s
Read: 43087 MB/s

And I got the same result with my other cards like a Panasonic 32 GB Class 10 and my 1 GB Omnitech Class 4!

It looks like the reader is faster than the card!
 
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