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In particular you cannot provide an internal SLA on write requests to low-level storage solutions if you can't guarantee that you actually have the spare disks.
by anthony_r 6y ago
In particular you cannot provide an internal SLA on write requests to low-level storage solutions if you can't guarantee that you actually have the spare disks.
The SLA would have to be something like "we guarantee 99.999% write availability unless team A or team B or team C makes a mistake", so now you have to look up what team A and B and C are up to and what do they guarantee. Instead of the more sensible "we guarantee 99.999% write availability unless you are out of quota".
- clavoie 6y agoExactly. At some point, someone somewhere will have a bad day / sneeze on a keyboard at just the perfectly wrong time -- at Google's scale, that's statistically a daily (hourly?) occurrence. Quota systems for the win -- if only as a shared agreement on who can do how much damage / take how much resources before they're automatically stopped and more resources must be justified through some review process (likely involving budgetary concerns).