sdxc card in laptop read/write speeds

[jaydee]

I have added a 128 GB SDXC card (PNY Elite performance) not so much for extra storage, but more for weekly backup. It's in a Latitude E6420 (Sandy Bridge), so I assume there are going to be some limitations to the read/write speed due to the bus architecture, but I'm finding the write speed to be ridiculously slow. In transferring files to the card, via the built-in SD card reader, the write speed was about 6 MB/s.

Now curious, I ran CrystalDiskMark and found the following:

Read
Seq Q32T1: 54.3 MB/s
4K Q32T1: 6.7 MB/s
Seq: 66.9 MB/s
4K: 6.3 MB/s

Write
Seq Q32T1: 6.55
4K Q32T1: 0.48
Seq: 15.73
4K: 0.55

I'd say the read speeds, while under spec of the card (up to 95 MB/s), can explained by the old architecture of the laptop. The write speeds are brutal though. I've seen other CrystalDiskMark benches of this on Amazon and have seen mostly 40-60 MB/s. Can anyone explain?

 

[hojnikb]

Is alignment correct ?

 

[Elixer]

Not a good idea to do backups on a card, they aren't meant for that type of workload, and the controller on the device isn't very good compared to a SSD.
That said, is write caching on?

 

[stlc8tr]

Which model SDXC card? I took a look at PNY's website and it seems most of their cards are UHS1 only, which would result in 15MB-20MB/sec writes. They only have one model that's UHS3, the Pro Elite, which is rated for 90MB/sec writes.

 

[jaydee]

Not a good idea to do backups on a card, they aren't meant for that type of workload, and the controller on the device isn't very good compared to a SSD.
That said, is write caching on?

The point for me, I want to keep stuff backed up, but I also want it to be "hidden", as in not a USB flash drive that sticks out, and not an external drive to plug and unplug. I just wanted something to plug in and not worry about when I undock and travel. It's not much of a workload, just end of the day or week copy some files over to the SD card.

The performance aspect isn't really a big deal, because it's really smaller incremental daily or weekly writes (usually no more than 50-100 MB at a time), it just struck me as odd that the writes were so slow... surely there's an explanation.

Which model SDXC card? I took a look at PNY's website and it seems most of their cards are UHS1 only, which would result in 15MB-20MB/sec writes. They only have one model that's UHS3, the Pro Elite, which is rated for 90MB/sec writes.

This is the one I have, you can find it on Amazon: PNY Elite Performance 128 GB High Speed SDXC Class 10 UHS-I, U3 up to 95 MB/Sec Flash Card (P-SDX128U395-GE)

 

[stlc8tr]

This is the one I have, you can find it on Amazon: PNY Elite Performance 128 GB High Speed SDXC Class 10 UHS-I, U3 up to 95 MB/Sec Flash Card (P-SDX128U395-GE)

Yeah, that's a UHS1 card so 15MB-20MB/sec writes are to be expected. The 95MB/sec figure is only for reads.

 

[jaydee]

Is alignment correct ?

Can you fill that out?

 

[jaydee]

Yeah, that's a UHS1 card so 15MB-20MB/sec writes are to be expected. The 95MB/sec figure is only for reads.

That doesn't explain the discrepancy between the 40-60 MB/s write speeds seen in screen shots on the Amazon reviews and the 6 MB/s write speed I am seeing.

 

[stlc8tr]

That doesn't explain the discrepancy between the 40-60 MB/s write speeds seen in screen shots on the Amazon reviews and the 6 MB/s write speed I am seeing.

You're right, I didn't look at the spec closely enough. That card is UHS1-U3 so that should mean faster than 20MB/sec writes.

Alignment usually isn't a concern with SD cards in Windows but you can try reformatting it with a utility known to align properly.

According to this blog entry, the official formatter will work.

https://www.sdcard.org/downloads/formatter_4/index.html

 

[Elixer]

... in a Latitude E6420 ...

Can you open up device manager, and look what card reader it is, and look if write caching is on?
Could be driver issues.

 

[Glaring_Mistake]

That doesn't explain the discrepancy between the 40-60 MB/s write speeds seen in screen shots on the Amazon reviews and the 6 MB/s write speed I am seeing.

Something that is good to remember to do on Amazon is checking exactly what capacity (and at times revision) they're reviewing.
Because reviews on Amazon are a mess, where they combine all capacities of an item which means you have to sort out what information is useful and what isn't.

So there is only one of the screenshots that shows results for that card at the same capacity while the others are of different capacities.
Still, his card does have much higher write speeds than yours and I don't know why yours doesn't perform as well as his.

 

[jaydee]

Can you open up device manager, and look what card reader it is, and look if write caching is on?
Could be driver issues.

The card reader is O2Micro Integrated MMC/SD controller. I tried updating the driver (dated 2011) and it says it's up to date.

"This device does not allow its write-caching settings to be changed"

 

[Cerb]

Any integrated reader giving you much more than 20MBps sequential read is generally pretty good, IMO. But, if you want the speed, you'll likely have to go buy a well-reviewed or known-good-brand (such as Lexar, Toshiba, or Sandisk) UHS USB 3.0 external card reader (I use a Lexar UR2, FI).

Computers come with cheap readers, to save money. The are fine for light duty, but are usually slow, sometimes painfully so.

By being Class 10, your card should write >10MBps sequential in a non-UHS reader, not 6MBps.

 

[Elixer]

The card reader is O2Micro Integrated MMC/SD controller. I tried updating the driver (dated 2011) and it says it's up to date.

"This device does not allow its write-caching settings to be changed"

I see newer drivers on the DELL site (dated 2015), checking via the upgrade button won't get those.

 

[jaydee]

I see newer drivers on the DELL site (dated 2015), checking via the upgrade button won't get those.

Just grabbed the latest drivers from Dell. That got me up to

Read
Seq Q32T1: 57.6 MB/s
4K Q32T1: 6.9 MB/s
Seq: 77.1 MB/s
4K: 6.6 MB/s

Write
Seq Q32T1: 9.6
4K Q32T1: 0.66
Seq: 17.62
4K: 0.72

That bought me a bit of extra write speed, but I'm still less than what I would expect. Out of curiosity, why would the Seq Q32T1 write be about half of the Sequential write? That's just que depth right, shouldn't it be about the same?

 

[hojnikb]

Just grabbed the latest drivers from Dell. That got me up to

Read
Seq Q32T1: 57.6 MB/s
4K Q32T1: 6.9 MB/s
Seq: 77.1 MB/s
4K: 6.6 MB/s

Write
Seq Q32T1: 9.6
4K Q32T1: 0.66
Seq: 17.62
4K: 0.72

That bought me a bit of extra write speed, but I'm still less than what I would expect. Out of curiosity, why would the Seq Q32T1 write be about half of the Sequential write? That's just que depth right, shouldn't it be about the same?

Nope, reading/writing a single block at a time is obviously slower, since you can't take the advantage of flash's parallelism. It gets even worse with multiple queue depth, since controllers inside cards handle those very poorly.

 

[Elixer]

That is one poor controller.
Unless they do more driver updates, looks like that is about all they can squeeze from this chipset.

 

[jaydee]

That is one poor controller.
Unless they do more driver updates, looks like that is about all they can squeeze from this chipset.

Update:

I tried this again on an Ivy Bridge Latitude, and the speeds were basically the same, biggest difference I was up about 10% on sequential writes.

Then I got my hands on an Ivy Bridge HP Elitebook, and that's where things got much better. Sequential read speeds up to the advertised ~90MB/s (up about 50% over the Latitude) and the Sequential write speeds were up to 33-36 MB/s (75-300% higher than Latitude). The 4k benchmarks both read/write are largely the same.

I guess the controller in the SB/IB Latitude is holding it back quite considerably. I'll have to see if I can find a Haswell to test for more data.

 

[Cerb]

If you want performance, buy a USB 3.0 reader from a brand camera people use. Good performance from an OEM integrated controller is unlikely to be impressive. Dell saving 10 cents is more important than you getting a card's advertised performance.

 

[jaydee]

If you want performance, buy a USB 3.0 reader from a brand camera people use. Good performance from an OEM integrated controller is unlikely to be impressive. Dell saving 10 cents is more important than you getting a card's advertised performance.

I actually do have one. Problem being, my laptop doesn't have native USB 2.0, so my read speeds are about half, down to ~30 MB/s. The sequential write speed is about 2.5x higher though (up to 22 MB/s).