[CentOS-mirror] How often to synchronize mirror?

Wed Jun 5 19:42:39 UTC 2019
Valeri Galtsev <galtsev at kicp.uchicago.edu>

On 2019-06-05 13:36, Anssi Johansson wrote:
> Valeri Galtsev kirjoitti 5.6.2019 klo 18.21:
>> Dear All,
>> I run public mirror (bay.uchicago.edu), and today I have noticed that 
>> the status page
>> https://mirror-status.centos.org/
>> shows in red it is not in sync for 5 hours, or so. It's been quite 
>> some time ago when I first installed it, and that time decent practice 
>> was to sync 3 times a day (about once every eight hours). More often 
>> was assumed to overwhelm higher tier source.
>> What is good practice these days: how often it is OK to synchronize 
>> mirror? I changed sync to every other hour (once I notices it shining 
>> red on mirror status page). Is that OK, or that will overwhelm higher 
>> tier mirror?
> My usual recommendation has been every 6 hours (4 times per day). Every 
> 4 hours (6 times per day) is also OK if more frequent syncs are desired. 
> It is also a good idea to pick a random minute to do the sync, so that 
> all mirrors would not try to sync at xx:00 (or xx:30 or some other round 
> number).

I switched to 6 times a day. I do not randomize minutes, I just picked 
some random number of minutes between 0 and 59 (different for different 
distributions we mirror). Thanks for guide line!

> A note about https://mirror-status.centos.org/ -- there are two columns 
> that have colourful markers. The first one signifies mirror age, and it 
> will turn blue if the mirror's age is between 1d + 4h and 2d + 4h, and 
> red if the mirror's age is more than 2d + 4h. If you sync(ed) every 8 
> hours, your mirror should not get marked as "red" because of the mirror 
> age.
> The other column, which does show some red for your mirror, signifies 
> reachability. Most probably your mirror was briefly unavailable today 
> for some reason. Everything seems to be OK now, so maybe it was just 
> some temporary glitch somewhere.

Thanks for explanation of what is what. "Reachability" problem seems odd 
to me, I need to look into that. I do not notice ever DOS level of 
requests, and the box should theoretically be tough. Networking people - 
at least so far - promised not to shape of filter in any way traffic in 
the block of IP addresses my servers use... Anyway, trouble must be on 
my own side, I'll look into that.

Thanks a lot!


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Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247