Operational Uptime

We’ve all heard companies that claim service reliability of “99.9%” or “99.99%” or “5 nines” (meaning 99.999%). But what does that mean?

The fact is that 99.999% uptime is really hard to achieve. On a monthly basis, 99.999% uptime means that your service is “down” for less than 26 seconds. Now, many services skate around this issue with fuzzy definitions of “down”. They might say that “downtime is defined as a majority of mailboxes being unavailable”. So a single mailbox being down might not be considered “downtime”. But as customers, if its your mailbox, that doesn’t sound quite right, does it? We usually have simpler definitions.

Anyway, GMail this morning has been down for 3 hours (at least) on my mailbox. Assuming they operate perfectly for the remainder of the month, that means they’ve dropped to only 99.58% availability this month. And, if they remain up with no downtime for the rest of the year, they’ve already missed the 5-nines, and are struggling at 99.96%! Given the outages I’ve seen, I think they’ve been down for at least 12 hours on my mailbox, so I think they are operating under the 99% level.

Oh well, I shouldn’t beat up on them too much. It is only beta, after all, right? But geez- with the $4B in the bank from their second IPO, I’d think they could ad least get to “two nines”. What about my god-given right to read email now?

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