Why is initial block download slow on Raspberry Pi 4 with SSD?

Question

Ran benchmarks using sysbench and CPU, memory and networking performance is very similar on Pi 4 vs Lenovo ThinkCentre M92p (both quad-core with 4GB of memory).

Which benchmarks reveal why IBD is considerably slower on Pi (weeks vs days)?

Answer 1

My best guess is:

• The RPi4 CPU is just way slower than the laptop CPU. They're both old designs (the RPi4 CPU from 2015, the laptop CPU from 2013), but the RPi4 one is significantly lower-power, and less performance-oriented. It wasn't until the Apple M1 CPU in 2020 that ARM systems appeared with performance that is competitive with desktop/laptop x86 CPUs.

• Disk. Especially if for example the RPi is using an internal SD card for holding the Bitcoin Core database, it will suffer tremendously from the latency compared to typical SSD/HDDs on desktop/laptop systems.

Answer 2

I can think of two possible reasons:

• One, the CPU in the PI is much slower. The M92p uses an x86_64 CPU architecture, while the Pi uses an ARM CPU. CISC processors use more power, but are much faster for some applications than RISC processors. I believe there have been some optimizations for ARM recently for Bitcoin Core, but I don't know how much of a difference it makes.

• Two, there are quite a few reads and writes to the hard drive during the synchronization. I would guess that your Pi's hard drive is connected via USB, while the hard drive in the M92p is connected via SATA. SATA is much faster than USB.

AES acceleration does not matter (AES is only used for wallet encryption, not for synchronization), and Bitcoin Core has no support for making use of it. It does have support for SHA256 acceleration on some CPUs, but the laptop CPU doesn't support it, and support for ARM acceleration will only be available in the 23.0 release.