Here are highlights from my meeting on 2019-07-31 with CERN IT experts in Ethernet L2 switches:
- there is no standard for power supplies/fans/management interfaces,
- power supplies
- 10 years ago hot-swappable (Field Removable Units) power supplies were not very common, now they are common in data centers
- the power supplies are bought for a given vendor and for a give model (no compatibility between models of the same vendor and between vendors)
- It is possible that the situation is better in servers - we should look into power supplies for servers
- typically, power supplies are installed from the back, but airflow can be different (part number)
- power supplies have fans, airflow of power supplies needs to agree with airflow in the switch.
- Power supplies are bought either with front-back or back-front airflow (two different part numbers), there is only one vendor for which the airflow direction is controlled with jumpers
- fans:
- no standard
- for most of the removable FANs, one can choose the direction of airflow, i.e. one can buy two types of the same FAN
- for non-removable fans, typically the airflow is front-to site or site-to-site
- most common: front to back
- for cooling PHYs/SFPs in front panel, the best airflow is front-to-back
- most common in data centers: front to back,
- it does happen (top-of-the-rack switches, i.e. in racks with other equipment, not data centers) that switches are installed with front panel to the back, in such case, the airflow needs to be reverted...
- management ports
- serial communication: miniUSB or RJ45, RS232 connector is not used in new switches (only old)
- Ethernet port: RJ45 is a must, some switches (not common) have also SFP for fiber connection (1Gbps)
- USB: in many switches, there is a USB connector which can be used to update firmware (upgrade or recovery)
- status:
- LEDs for port status: very often only one that indicates: status (link up), speed, and activity
- General status: most of the time LEDs, display is not so common, yet it happens
- localisation feature (LED or info on display): seems a useful feature, not really available in switches
- power/reset button
- many switches have no power button, only reset
- most of switches have reset button that is small one, i.e. the one that can be pushed only with needle
- if exists, it is in front
- if we want to support 10Gbps copper SFPs - be careful about the heat - they heat up a lot
- a useful thing that is rarely available in switches (only one vendor): rails for mounting