Ciao, on the CMS-Eu redirectors I implemented as explained here:
we have 2
redirectors (xrootd.ba.infn.it and xrootd-redic.pi.infn.it), under DNS RR
xrootd-cms.infn.it
Now redirectors' configs read
all.role manager
all.manager xrootd-cms.infn.it+ 1213
all.manager meta any
cms-xrd-global.cern.ch+ 1098
which I understand is the advised solution. What I see is strange.
if I do
something like
xrdcp -d 3 root://xrootd-redic.pi.infn.it//store/test/xrootd/T2_ES_IFCA/store/mc/SAM/GenericTTbar/GEN-SIM-RECO/CMSSW_5_3_1_START53_V5-v1/0013/CE4D66EB-5AAE-E111-96D6-003048D37524.root .
>>>>Why did you go directly to a particular redirector. Why didn’t you use xrootd-cms.infn.it? It would seem that if you want access to one or the other you would use the higher level name.
and I look into the logs, I see this goes
xrootd-redic.pi.infn.it:1094
-> xrootd.ba.infn.it:1213 ALWAYS
(so indeed xrootd-redic.pi.infn.it:1213
does not seem to be serving files at all).
If I switch off
xrootd.ba.infn.it:1213, xrootd-redic.pi.infn.it:1213 starts to serve files, but
as soon as I start again xrootd.ba.infn.it:1213, the latter gets all the
traffic.
>>>Well, I am still confused. As none of the examples use xrootd-cms.infn.it as the target I don’t know what is going on. Going directly to “redic” goes directly to that.
I tried with things like
all.manager any/all xrootd-cms.infn.it+ 1213
(never really understood the difference any/all, my fault ...), but this does not seem to change the picture
>>>There is now a good explanation of all/any in the manual (see link at the end). However, it has nothing to do with clients so specifying all or any will have no effect on client access.
eventually, on xrootd-redic.pi.infn.it cmsd.log I see traffic (with
grep
serving cmsd.log
) only when the other cmsd is down ... is this expected? is
there a way to make sure
all.manager xrootd-cms.infn.it+ 1213
balances the cmsd calls between RR-DNS hosts?
>>>DNS RR is immaterial here. The above directive simply says that your data servers have two managers (redic and ba) and they will subscribe to both. A client needs to access these redirectors via the higher level name (xrootd-cms) to get access to one or the other. The choice is random and the load would be uniformly distributed to each of the xrootd front-ends across all of the clients. In turn, those xrootd-front ends subscribe to the cmsd back ends (one on redic the other on ba). If you specify “all” then the xrootd front-ends will distribute the load across the two cmsd back ends. The default, any, uses a simple fail-over model (as you saw). The concept is described here:
http://xrootd.org/doc/dev4/cms_config.htm#_Toc384307771
Andy