I eventually made up my mind on the choice of single-board computers (SBC) that will assist and eventually replace the role of my Asus RT-AC56U as an always-on home server. It's not a Raspberry Pi. My workload will be more towards server side and headless. I won't need, for example, WiFi and camera interface but would be good to have gigabit Ethernet, USB 3.0 and SD socket supporting UHS-I. More to come on my pick once I take the shipment and play with it.
One consideration that took unbelievably longer time to decide is a Micro SD card that will be used as system partition on my SBC. Actually it's not specific to Micro SD cards but picking flash thumbdrives in general. I'm not exactly new to this game. After reading people's research in the SBC communities, I feel like entering a new world, facinating!
A1/A2 application performance classes
To begin with, perhaps we shall start with Android. In earlier years, Android allows people to install applications on Micro SD cards. Later this feature was removed. Now this feature is (or will be) resurrected, thanks to new categories of Micro SD cards that support A1/A2 classes.
A1 class specifies a Micro SD card capable of minimum 1500 read and 500 write random I/O operations per second (IOPS), each operation consisting of a 4KiB chunk. A2 class cards could perform minimum 4000/2000 random R/W IOPS. Random read/write of small chunks is typical workload of operating systems and applications. Its performance is critical for smooth app experience. More details on A1/A2 classes can be found on SD Association's whitepaper (in pdf format).
iozone benchmark tool
The concept behind A1/A2 classes is equally applicable to USB thumbdrives used for running applications on routers, single-board computers and other IoT devices. On Windows, we have well known benchmark tools e.g. CrystalDiskMark and ATTO Disk Benchmark. On Mac, there is Blacmagic Disk Speed Test. I've never questioned how these benchmarks are implemented. But have seen results on the same USB stick could vary a lot from different tools.
The SBC communities appear to favor a tool called iozone that is not only open source but descently designed and widely available on all platforms. That makes even cross-platform comparison a possibility. If you happen to run Entware on ARMv7 (32-bit) or ARMv8 64-bit devices, you may get my compiled iozone binaries. Instructions follow.
Entware armv7 installation
$ wget -qO- https://gitlab.com/kvic/Entware-Goodies/raw/master/iozone-v3.482-armv7.tar.gz | tar xf - -C /jffs/bin
Note: e.g. Asus RT-AC56U/68U/87U/88U. The above command line installs
/jffs/bin with another path of your choice.
Entware aarch64 installation (armv8 64-bit)
$ wget -qO- https://gitlab.com/kvic/Entware-Goodies/raw/master/iozone-v3.482-aarch64.tar.gz | tar xf - -C /jffs/bin
Note: e.g. Asus RT-AC86U
$ rm /jffs/bin/iozone
Run the benchmark
iozone will test the target drive of your current directoy and operations are non-destructive to the drive. It creates a temporary file of size specified in
-s for read and write and delets the file after test done.
$ cd /opt $ /jffs/bin/iozone -e -I -a -s 20M -r 4k -r 16k -r 512k -r 1024k -r 16384k -i 0 -i 1 -i 2 random random kB reclen write rewrite read reread read write 20480 4 4628 4697 19021 19119 6206 3977 20480 16 16030 16768 51271 50867 22272 13536 20480 512 48162 75564 91575 92086 80767 67474 20480 1024 53266 86650 92302 95623 89220 78823 20480 16384 71618 88822 107486 107510 107406 87864
First row represents the read/write performance of chunk size 4KiB. The next row 16KiB and so on. For operating systems and application use, the random read/write of 4KiB chunks is a critical metric. All throughputs are in KiB/s. Divide the numbers from first row and last two columns by 4, you get IOPS roughly. Alternatively, specify '-O' so that
iozone display throughputs in IOPS.
The above result shows the throughput of my SanDisk Ultra Flair 64GB USB 3.0 purchased a few years ago. Converting the random read/write into IOPS, my stick has 1551.5 for read and 994.25 for write. Those numbers appear slightly exceeding A1 class.
Over the years, I think memory cards (including USB sticks) are one of the most lucrative products in tech commodities. Vendors charge premium for promoting maximum sequential read speed. Under perform on everyday tasks except copying large files from the memory cards.
I would love to see results on a variety of cards here or elsewhere by running iozone. Keep them coming in!