6 ms·

We had a very similar situation recently where the colocation facility had replaced some missing block-out panels in a rack and it caused the top-of-rack switch

We had a very similar situation recently where the colocation facility had replaced some missing block-out panels in a rack and it caused the top-of-rack switches to recycle hot air... the system temps of both switches were north of 100°C and to their credit (dell/force10 s4820Ts) they ran flawlessly and didn't degrade any traffic, sending appropriate notices to the reporting email. Something as benign as that can take out an entire infra if unchecked. I've seen racking fail in the past (usually someone loading a full 42U with high density disk systems putting the rack over weight capacity by a notable factor) and it is definitely a disaster situation. One datacenter manager recounted a story of a rack falling through the raised flooring back in the days when that was the standard (surprise - it kept running until noticed by a tech on a walkthrough). Good story but comes across as back-patting a bit.

hinkley 7y ago
Last time this line of discussion came up someone confessed that they discovered they’d accidentally made an exhaust fan into an intake fan thereby blowing hot air across their cpu into their drives and nearly baking them.
- dfox 7y ago
  Most rackmount switches are not really designed to be used in datacenter rack as they do not have front-to-back airflow (and even if they would have, networking hardware tends to have all connectors on wrong side of the box). But almost everyone routinely does that which then necessitates knowing that installing all air baffles would lead to exactly this issue.
  - dnautics 7y ago
    > Most rackmount switches are not really designed to be used in datacenter rack as they do not have front-to-back airflow It's my understanding that switchable fans are standard on cisco, arista, and mellanox switches (have no idea about juniper) and besides, front-to-back or back-to-front depends on whether you mount in the back or in the front (both are valid) AND even if you go the "wrong way" patch panels are pretty easy to find and are cheap (at the expense of 1U)
    - dfox 7y ago
      On high-end-ish switches that are truly designed for this application. And having switchable fans will not help you with device that has left-to-right (or even more weird) airflow.
  - deleted 7y ago
    [deleted]
  - hinkley 7y ago
    It's been too long since I've been into a server room. It was not uncommon to see half-depth switches in the era prior to 'hot aisles' and I definitely recall them pulling air in directions that you might not like. They were never deep enough to siphon air from the front of the rack. If you have a switch fully populated rail-to-rail with ethernet jacks, it's not entirely clear to me where you should route air in a hot/cold aisle setup.
philosopher1234 7y ago
Whats wrong with back patting? They did a good job
- RichardCA 7y ago
  There was an air of condescension, as if no one else had ever figured out how to run a data center before.
  - Godel_unicode 7y ago
    It didn't read that way at all to me, what wording leads you to that impression?

hinkley 7y ago

Last time this line of discussion came up someone confessed that they discovered they’d accidentally made an exhaust fan into an intake fan thereby blowing hot air across their cpu into their drives and nearly baking them.

dfox 7y ago
Most rackmount switches are not really designed to be used in datacenter rack as they do not have front-to-back airflow (and even if they would have, networking hardware tends to have all connectors on wrong side of the box). But almost everyone routinely does that which then necessitates knowing that installing all air baffles would lead to exactly this issue.
- dnautics 7y ago
  > Most rackmount switches are not really designed to be used in datacenter rack as they do not have front-to-back airflow It's my understanding that switchable fans are standard on cisco, arista, and mellanox switches (have no idea about juniper) and besides, front-to-back or back-to-front depends on whether you mount in the back or in the front (both are valid) AND even if you go the "wrong way" patch panels are pretty easy to find and are cheap (at the expense of 1U)
  - dfox 7y ago
    On high-end-ish switches that are truly designed for this application. And having switchable fans will not help you with device that has left-to-right (or even more weird) airflow.
- deleted 7y ago
  [deleted]
- hinkley 7y ago
  It's been too long since I've been into a server room. It was not uncommon to see half-depth switches in the era prior to 'hot aisles' and I definitely recall them pulling air in directions that you might not like. They were never deep enough to siphon air from the front of the rack. If you have a switch fully populated rail-to-rail with ethernet jacks, it's not entirely clear to me where you should route air in a hot/cold aisle setup.

philosopher1234 7y ago

Whats wrong with back patting? They did a good job

RichardCA 7y ago
There was an air of condescension, as if no one else had ever figured out how to run a data center before.
- Godel_unicode 7y ago
  It didn't read that way at all to me, what wording leads you to that impression?