ciao Andy!
- I am pinging directly to xrootd-redic.pi.infn.it (and not to the DNS RR)
since I did not modify the other copy. did not want to risk too much here
(for the reason I am trying to explain below)
I have a doubt about the picture you sent via the link. It makes sense only
if all cmsd and xrootd are equal. In our setup (with ~40 sites connected),
we had before only xrootd.ba.infn.it as redir. Now we asked the sites to
move to xrootd-cms.infn.it, but after two weeks ~ 50% of the sites moved (a
lot of inertia, but it is difficult to go and twist arms ...).
so let's suppose
- xrootd.ba.infn.it has 50 servers registered in cmsd
- xroot-redic.pi.infn.it has 30.
what would happen if
xrootd.ba.infn.it:1094 -> xrootd-redic.pi.infn.it:1213 (which can happen if
I put as manager for xrootd.ba.infn.it the DNS RR...) ?
the cmsd would not have all the servers registered, and hence fail can fail
on a file? it can even be ok if fail means go up to the global redirector,
and then down to xrootd.ba.infn.it:1213 (even if at this point a random EU
or US site would be used).
So, how if the picture changing if the cmsd cannot be considered identical
as # of connected servers?
I know the correct answer would be "force them to change", but .... ok, I
guess you understand ;)
thanks a lot
tom
On Tue, Jul 8, 2014 at 11:37 PM, xrootd-dev <[log in to unmask]>
wrote:
> Hi Tommaso,
>
>
>
> From: Tommaso Boccali
> Sent: Monday, July 07, 2014 11:33 PM
> To: xrootd/xrootd
> Cc: xrootd-dev
> Subject: Re: [xrootd] xrootd fallback only populates "tried" for one
> redirector (#124)
>
> 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
>
> The known managers
> 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
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/xrootd/xrootd/issues/124#issuecomment-48402749>.
>
--
Tommaso Boccali
INFN Pisa
—
Reply to this email directly or view it on GitHub.
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