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Rive
Posts: 586
Joined: Sat Mar 26, 2016 5:21 pm
Location: USA

Pi3 slow write to Sandisk Pixtor 64GB UHS-1 XC-1 cards?

Wed Apr 27, 2016 7:44 pm

I have been using a Samsung EVO+ SDHC 32GB card which averages around 20 MB/s Write, and 40 MB/s Read speeds.

I figure I would get a larger capacity sdcard, so I acquired a Sandisk 64GB Pixtor SDXC. It is rated for speeds up to 80 MB/s read/write.

It is super slow though, averaging around 13 MB/s Write speeds. So I am wondering if the pi3 (rasbian jesssie) has some kind of difficulty with these larger SDXC cards, or perhaps an issue particular to Sandisk Pixtor cards?

I used DD Bench (but results were also verified with Sdbench)

Code: Select all

dd if=/dev/zero of=./largefile bs=1M count=1024
sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
dd if=./largefile of=/dev/null bs=1M count=1024

Image
32GB Samsung EVO+ UHS-1 SDHC (rated at maximum 80 MB/s Read, and 20 MB/s Write)

Code: Select all

dtparam=sd_overclock=100
5 passes (write/read 1.1 GB) :
22.1 W 42.9 R
22.7 W 43.0 R
18.1 W 43.2 R
18.6 W 39.9 R
19.6 W 43.3 R


Image
64GB Sandisk PIXTOR UHS-1 SDXC (rated at maximum 80 MB/s Read/Write)

(note- Write speeds are the same for the Sandisk Pixtor regardless of whether sd_overclock is enabled or not as if the pi3 is not fully utilizing the card speeds like it does for the Samsung EVO+)

Code: Select all

dtparam=sd_overclock=100
5 passes (write/read 1.1 GB):
12.5 W 42.4 R
13.9 W 42.3 R
13.4 W 42.3 R
13.7 W 42.0 R
14.0 W 38.3 R

DDBench:

Code: Select all

[email protected]:~ $ dd if=/dev/zero of=./largefile bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 86.2351 s, 12.5 MB/s
[email protected]:~ $ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
[email protected]:~ $ dd if=./largefile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 25.3318 s, 42.4 MB/s
[email protected]:~ $ dd if=/dev/zero of=./largefile bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 77.3016 s, 13.9 MB/s
[email protected]:~ $ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
[email protected]:~ $ dd if=./largefile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 25.3816 s, 42.3 MB/s
[email protected]:~ $ dd if=/dev/zero of=./largefile bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 80.2591 s, 13.4 MB/s
[email protected]:~ $ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
[email protected]:~ $ dd if=./largefile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 25.3545 s, 42.3 MB/s
[email protected]:~ $ dd if=/dev/zero of=./largefile bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 78.5961 s, 13.7 MB/s
[email protected]:~ $ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
[email protected]:~ $ dd if=./largefile of=/dev/null bs=1M count=10241
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 25.5396 s, 42.0 MB/s
[email protected]:~ $ dd if=/dev/zero of=./largefile bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 76.4454 s, 14.0 MB/s
[email protected]:~ $ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
[email protected]:~ $ dd if=./largefile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 28.0115 s, 38.3 MB/s
Sd_overclock enabled:12 MB/s Write

Code: Select all

[email protected]:~ $ sudo ./sdbench.sh
#[3;J
CONFIG: 
CLOCK : 100.000 MHz
CORE  : 500 MHz, turbo=1
DATA  : 512 MB, /root/test.dat

HDPARM:
======
 Timing O_DIRECT disk reads: 128 MB in  3.02 seconds =  42.36 MB/sec
 Timing O_DIRECT disk reads: 128 MB in  3.01 seconds =  42.51 MB/sec
 Timing O_DIRECT disk reads: 128 MB in  3.03 seconds =  42.21 MB/sec

WRITE:
=====
536870912 bytes (537 MB) copied, 42.3342 s, 12.7 MB/s
536870912 bytes (537 MB) copied, 41.1442 s, 13.0 MB/s
536870912 bytes (537 MB) copied, 43.2825 s, 12.4 MB/s

READ:
====
536870912 bytes (537 MB) copied, 15.0266 s, 35.7 MB/s
536870912 bytes (537 MB) copied, 12.6376 s, 42.5 MB/s
536870912 bytes (537 MB) copied, 12.6425 s, 42.5 MB/s

RESULT (AVG):
============
Overlay config                      core_freq   turbo   overclock_50    WRITE        READ        HDPARM
                                       500        1     100.000 MHz   12.12 MB/s 38.36 MB/s   42.38 MB/s


Sd_overclock disabled:11 MB/s Write

Code: Select all

[email protected]:~ $ sudo ./sdbench.sh
#[3;J
CONFIG: 
CLOCK : 50.000 MHz
CORE  : 500 MHz, turbo=1
DATA  : 512 MB, /root/test.dat

HDPARM:
======
 Timing O_DIRECT disk reads:  68 MB in  3.08 seconds =  22.11 MB/sec
 Timing O_DIRECT disk reads:  66 MB in  3.01 seconds =  21.95 MB/sec
 Timing O_DIRECT disk reads:  66 MB in  3.01 seconds =  21.91 MB/sec

WRITE:
=====
536870912 bytes (537 MB) copied, 47.2213 s, 11.4 MB/s
536870912 bytes (537 MB) copied, 47.0887 s, 11.4 MB/s
536870912 bytes (537 MB) copied, 44.0913 s, 12.2 MB/s

READ:
====
536870912 bytes (537 MB) copied, 29.7666 s, 18.0 MB/s
536870912 bytes (537 MB) copied, 24.8969 s, 21.6 MB/s
536870912 bytes (537 MB) copied, 23.856 s, 22.5 MB/s

RESULT (AVG):
============
Overlay config                      core_freq   turbo   overclock_50    WRITE        READ        HDPARM
                                       500        1      50.000 MHz   11.11 MB/s   19.74 MB/s   21.98 MB/s
Last edited by Rive on Fri Apr 29, 2016 10:09 pm, edited 3 times in total.
DNPNWO

User avatar
Rive
Posts: 586
Joined: Sat Mar 26, 2016 5:21 pm
Location: USA

Re: Pi3 slow write to Sandisk Pixtor SDXC cards?

Fri Apr 29, 2016 9:43 pm

Anyone else notice this slow write issue with Sandisk pixtor? is it just my card?, or is the failing of the pi3?
DNPNWO

thecommentator
Posts: 3
Joined: Mon Mar 04, 2013 7:21 pm

Re: Pi3 slow write to Sandisk Pixtor 64GB UHS-1 XC-1 cards?

Wed Jun 15, 2016 6:38 pm

It may not be an issue with the Pixtor. The questions are whether the Pi can switch to 1.8V SD operation, and is SDXC write performance degraded when formated FAT32?

See my post: viewtopic.php?p=994571#p994571

Romonga
Posts: 123
Joined: Mon May 09, 2016 7:09 pm
Location: Montgomery Il

Re: Pi3 slow write to Sandisk Pixtor 64GB UHS-1 XC-1 cards?

Wed Jun 15, 2016 6:56 pm

ITs important to understand that those speed ratings don't tell the complete picture.

The Raspberry Pi uses a 4k block size. Any performance tests need to do a test on that block size. I have tested cards that were supper fast, until I placed it into the Pi. After testing it, I found that the SD card was only getting about .5 MB per sec on the 4k block size test. However, all other tests showed the card to be smoking fast.

Failure to get a card that can read and write 4k block size fast enough and you now have a crippled Pi.
You can run, but you will only die tired.

drgeoff
Posts: 9886
Joined: Wed Jan 25, 2012 6:39 pm

Re: Pi3 slow write to Sandisk Pixtor 64GB UHS-1 XC-1 cards?

Wed Jun 15, 2016 7:38 pm

thecommentator wrote: .. and is SDXC write performance degraded when formated FAT32?
That is irrelevant to this thread. The Raspbian root file system, even when Raspbian is installed via NOOBS, is not FAT32. (Nor FAT, nor exFAT.)

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