docs.daveops.net

Snippets for yer computer needs

Electronic hardware

FPGA

Parts manufacturers/distributors/sellers

Documentation

Snippets

Fuses

Slow blow fuses:

theory

Voltage

symbol: V (sometimes E) measured in volts voltage is between 2 points

Current

symbol: I measured in amps current is through a circuit

Arduino

http://ardx.org/src/code/

Raspberry Pi

Installing Fedora

dnf install -y fedora-arm-installer
fedora-arm-image-installer --image=</path/to/fedora_image> --target=<RPi_Version> --media=/dev/<sd_card_device> --resizefs

Pi 3

UART

Because of a firmware issue, need to add this to /boot/config.txt:

enable_uart=1

See also the GH issue

Oracle Integrated LOM

Turn on indicator light

3.0

show /SYS/LOCATE
set /SYS/LOCATE value=Fast_Blink

Turn server off

stop /SYS

usb

Cable

RAID levels

Level Data distribution Performance Space availability Redundancy
0 Data is striped over multiple disks. Higher read/write perf, since it’s split over disks All disks are available as one pool None - loss of one disk is catastrophic
1 Data is mirrored over multiple disks Read performance increased since multiple blocks can be accessed at the same time. Write perf declines since data must be written twice Available disk is effectively halved. Loss of 1 disk is non-catastrophic
4 Data striped over multiple disks. Parity information on separate disk Read operations benefit by striping. Writes are bottlenecked on the parity disk More efficient use of data redundancy with parity disk If parity disk is lost, data redundancy is lost
5 Data and parity striped over multiple disks Read operations benefit by striping   Can only handle one disk failure before data loss
6 Data and dual parity blocks striped over multiple disks Read operations benefit by striping   Can handle two disk failures before data loss
10 Hybridizing of 1 + 0, striping over mirrored sets Read operations benefit by striping