| Re: Aw: Re: Re: [chrony-users] How to use Facebook's NTP-service correctly? |
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Lars-Daniel.Weber@xxxxxx said:
> So for logging on a webserver (with database and stuff), you'd recommend to
> use Holger's settings?
You are missing the big picture.
The idea is that if you are a company like Google with zillions of database
servers that you want to run on smeared time, you setup the few NTP servers at
the top of your NTP tree to give out smeared time. Then you don't have to
change anything on your internal NTP servers or database servers. They don't
know they are running on smeared time. They just follow the time from the top
NTP servers.
(I'm using the term "database servers" to distinguish them from NTP servers.)
If you want your systems to run on smeared time, there are two approaches.
You can point all your internal systems running NTP at external smearing
servers. Google and Facebook run public smearing NTP servers. I don't know
of any others. That works if you have only a few systems. Just point them
all at smearing servers.
If you have enough database servers in your system, you probably have an
internal NTP tree and a few NTP servers at the top. You can point those top
NTP servers at non-smearing servers and set them up to give out smeared time.
If you do that, you probably don't want to run anything else on those top
boxes. They will be running on true time which will be offset from the time
on the rest of your machines while a smear is in progress so log files won't
match up.
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A key idea is that a NTP server should point to either all smearing or all
non-smearing servers, not a mix.
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If you do run a system (NTP or database) on smeared time, you need to make
sure that you don't tell it about the leap file.
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