I have a team of 4 DBAs - 2 SQL and 2 Oracle. We manage administer:

270 SQL Servers -dev, test, UAT and production

70 Oracle on Linux servers - dev, test, UAT and production

So, thats 135 servers/SQL DBA and 35/Oracle DBA.

The only we we can achieve this is by working 24x7 and not taking any sick days or vacation :-D.

But, seriously, we achieve this through standardising on builds, monitoring scripts and alerting. Most of our servers are exactly the same in configuration. When we perform tasks we always do it on server groups not individual servers. Strict change management also helps here.

We're helped to a degree by a seperate infrastructure team who builds the servers and a tier 1 support team who respond to alerts. Also, many of our servers are commodity, 'scale-out' servers so even the databases are exactly the same.

Oracle DBAs perform secondary support to SQL and Vice Versa.

Its pretty tough and we could do with a couple more DBAs but the budget aint there. Its the 'new normal' i.e. doing more with less.

In a previous post at a gaming company who solely used SQL Server the ratio was 10:1 - we had 10 DBAs and about 120 servers to manage. In hindsight this was overkill and I only realise now how much you can save by standardisng kit and unifying your processes instead of adding more and more DBAs.