Topic: Strange yum fast mirror times

[Marco Hess]

On one of my servers, the yum update reports is showing a log of the times being measured to the various mirrors.

I suspect that this is the fastmirror yum plugin.

However I find the measured times very strange. For example the list below is what it shows (after a bit of cleanup and sorting).

sme-mirror.firewall-services.com is at the top of the list with times or around 1ms while this server is halfway around the world from me (I am in Australia). Ping roundtrip is measured at 370ms.

--- sme-mirror.firewall-services.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 371.730/371.730/371.730/0.000 ms, pipe 2

Similarly my own ISP (internode) is only listed 16th down the list with 0.59s. while it has a 20ms round trip.

--- mirror.internode.on.net ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 20.189/20.189/20.189/0.000 ms, pipe 2

If this fastest mirror plugin is supposed to select your closest mirror, I don't think it is doing that. 

Code: [Select]

sme-mirror.firewall-services.com 0.001040 secs
ftp.swin.edu.au                  0.001651 secs
distro.ibiblio.org               0.003583 secs
mirror.aarnet.edu.au             0.003873 secs
mirror.xcb567.ath.cx             0.003905 secs
sme-mirror.voxteneo.com          0.004842 secs
mirror.optus.net                 0.049088 secs
mirror.primusdatacentre.com.au   0.058208 secs
mirror.pacific.net.au            0.216761 secs
ftp.surfnet.nl                   0.302533 secs
mirror.intrapower.net.au         0.349576 secs
ftp.nluug.nl                     0.406110 secs
mirror.3fl.net.au                0.497821 secs
ftp.monash.edu.au                0.504716 secs
smeserver.hkisl.net              0.566560 secs
mirror.internode.on.net          0.593322 secs
centos.mirror.aussiehq.net.au    0.650555 secs
smemirror.fullnet.co.uk          0.701216 secs
hosting.platiniumtv.ro           1.108417 secs
www.percheron.info               1.224783 secs
mirror.nus.edu.sg                1.652514 secs

[cactus]

I am not sure how yum does it's timing, but I do not think it is ping only as this does not say much about actual download speed for instance as this is one of the most important things in a yum update process. Resolving host names and reaching them IMHO is only a minor part of it.

According to this mail on the yum mailing list it times the connection on how long the connect function takes. I have not dived into the source to see what it does in there, but you can find references to it on this page: http://yum.baseurl.org/

[Marco Hess]

On my main system it is much more sensible with my ISP listed as the top choice:

Code: [Select]

mirror.internode.on.net          0.025124
ftp.monash.edu.au                0.030884
ftp.swin.edu.au                  0.035662
mirror.primusdatacentre.com.au   0.036319
mirror.pacific.net.au            0.049262
mirror.optus.net                 0.051899
mirror.intrapower.net.au         0.061235
mirror.aarnet.edu.au             0.061638
distro.ibiblio.org               0.281423
centos.mirror.aussiehq.net.au    0.283438
ftp.nluug.nl                     0.366569
smemirror.fullnet.co.uk          0.367162
ftp.surfnet.nl                   0.367697
ftp.rgmtechnical.nl              0.369688
sme-mirror.voxteneo.com          0.370108
sme-mirror.firewall-services.com 0.384820
hosting.platiniumtv.ro           0.436388
mirror.3fl.net.au                0.438871
mirror.nus.edu.sg                0.448938
smeserver.hkisl.net              0.779542
www.percheron.info               2.134882
mirror.xcb567.ath.cx             3.140450

The timings in a previous post is a VMware based server (running on this main system) so maybe that has something to do with it.

[cactus]

The timings in a previous post is a VMware based server (running on this main system) so maybe that has something to do with it.

Perhaps, how accurate is the system time on your virtual system? Do you have some form of time syncing enabled?

[Marco Hess]

I think at some time in the past I must have done something (but I can't remember) as all these virtual servers are pretty much on the dot with the time on the host server.

As far as I can tell from the /var/cache/yum/timedhosts.txt files on each of the virtual machines, they are all out of whack in terms of their timings (both SME7 and SME8 machines).

[cactus]

As far as I can tell from the /var/cache/yum/timedhosts.txt files on each of the virtual machines, they are all out of whack in terms of their timings (both SME7 and SME8 machines).

What if you move it out of the way and try again? It should recalculate and regenerate the list.

[Marco Hess]

Moved the timedhosts.txt away and let it recreate. Still very weird results. Note that in a proper result the fastests time is still some 25ms or so. In the results below, the fastest times are 0.5ms!

Code: [Select]

smemirror.fullnet.co.uk         0.000524044036865
mirror.3fl.net.au               0.000569105148315
ftp.surfnet.nl                  0.000626087188721
mirror.pacific.net.au           0.000701904296875
distro.ibiblio.org              0.00074291229248
ftp.tcc.edu.tw                  0.000756978988647
mirror.primusdatacentre.com.au  0.000771999359131
centos.mirror.aussiehq.net.au   0.000790119171143
mirror.nus.edu.sg               0.000826835632324
ftp.swin.edu.au                 0.00150394439697
ftp.nluug.nl                    0.00235795974731
ftp.monash.edu.au               0.00353407859802
mirror.intrapower.net.au        0.00397992134094
mirror.internode.on.net         0.00403594970703
sme-mirror.voxteneo.com         0.00426006317139
mirror.optus.net                0.00506901741028