Sonntag, 28. Dezember 2014

Set -XX:-UsePerfData for 24/7 java-apps on your raspberry

The "official" raspberry pi distribution raspbian doesn't use tmpfs for /tmp. Therefore, all applications storing temporary stuff in /tmp cause writes to the rootfs which in most cases means to the SD card.

Usually the few kilobyte every minute are no big deal.
However, if you plan to deploy raspberry pi based systems running java applications 24/7 for years every unnescessary periodically occurring write counts.

So, beside using only high-quality SD cards (with MLC or SLC flash), you might want to run your java apps with -XX:-UsePerfData specified. This flag instructs hotspot to no longer generate temporary files for performance monitoring in /tmp.

Freitag, 12. Dezember 2014

Odroid C1 - finally a worthy Raspberry Pi successor

For quite some time I was unhappy about the state of ARM based linux boards:

There was/is the Raspberry Pi which is cheap and widely supported, however extremly underpowered and its creators are reluctant to move to a more powerful Soc (the soc manufacturer employs the Raspberry Pi's main developer, so no suprise). The Raspberry Pi features a single-core ARM11 CPU running at 700Mhz - the same CPU design which was used for the original IPhone in 2007. Worse, due to its age, it doesn't support the ARMv7 instruction set.

The other choice one had were boards with powerful dual and quad-code socs featuring powerful out-of-order cores running at 1-1,5ghz. The downside: Price. Those boards were in the range of 50-100$. For 41€ I can get a mainboard with a dual-core x86 APU (+20€ für 2GB DDR3 ram), where OpenGL is supported by open-source drivers, so no ARM in this price range.

However, recently Hardkernel has announced the Odroid C1. The Ordoid C1 seems to be a perfect compromise between price and performance. For the same price of a Raspberry Pi you get quad-core design. Granted, you only get Cortex-A5 cores (in-order, single-issue) which perform clock-for-clock more or less like the ARM11 found in the raspberry - however you get 4 of them clocked at twice the frequency. Plus, you get twice the amount of RAM (1GB instead of 512MB).

ODroid C1 (Source: Hardkernel)