There are several useful QoS parameters, although not all are as easily measured as e.g. 99.98% uptime, which is easily derived – 99.98% of the time, your server is available.
Some other useful metrics:
- What sort of bandwidth do they support? How about if it’s a shared pipe and they’ve multiple high-volume clients? You’re unlikely to get an honest answer to this from the vendor.
- If you’re on a shared host, what sort of competition for resources will you have on the box? Again, this is competitive information, so you’re unlikely to get an honest response.
- How independent is each application? i.e. if another application on a co-hosted box loops MySQL, will your app suffer?
- How often do they upgrade dependencies, and does that affect their 99.98% uptime?
Then there are the fluffy not-entirely-QoS related hosting problems:
- Will they do your backups etc.?
- How responsive are they to queries? Do they have a guaranteed response time e.g. 3 hours from first email to first response, 24/7?
- Are they efficient? Have they resolved issues within a useful timeframe? A quick response-time is nice and feelgood, but if they don’t fix the problem, that’s not quite so good!
- Are they patient with you when you suggest issues, but due to your own technical background are slightly off-base?
Of course you could always do your own backups, with external drives like this, or caddies (2.5″, 3.5″) for old spare hard drives you have lying around, but that doesn’t substitute for the technical support you get from a good host.