Hi Derek,
Bill and Teela have been doing such measurements for some time now and would
be the best sources of information. Bill and Teela?
Andy
----- Original Message -----
From: "Derek Feichtinger" <[log in to unmask]>
To: "Fabrizio Furano" <[log in to unmask]>
Cc: "xrootd-list" <[log in to unmask]>
Sent: Monday, April 03, 2006 9:26 AM
Subject: Re: benchmark for distributed I/O?
> Hi, Fabrizio
>
> I need to ensure that _every_ CPU core (i.e. every job) can read at a
> steady
> rate from the storage space made up by the file servers. 4MB/s per job is
> what we will require, but the CMS TDR has set higher values. These however
> seem to be ignored by most centers as over the top. A discussion with a
> member of the storage task force seems to indicate that most centers go
> for a
> 2MB/s per job rate.
>
> The XrdMon will be nice to measure the complete xrootd system's
> performance,
> but I need to define an easily measurable and well defined procedure which
> can be used for the bidding companies. I could sure use xrootd to compose
> such a procedure and I was initially thinking about that. I just want to
> get
> an overview what has been used by others.
>
> If I was to use xrootd, I would try to get the clients to read at a given
> rate. Then I could look at the server statistics. I would gradually
> increase
> the specified rate and look at the actually measured rate.
>
> The nice thing about using xrootd naturally is that it is one of the tools
> used for the real case.
>
> BTW: A good link about measurement techniques (but not containing the
> definite
> answer to my problem) is here
> http://dast.nlanr.net/NPMT/
>
> Thanks,
> Derek
>
>
> On Monday 03 April 2006 17.59, Fabrizio Furano wrote:
>> Hi Derek,
>>
>> Derek Feichtinger wrote:
>> > Hi,
>> >
>> > This is slightly off-topic, but nontheless important for the setup of
>> > large direct attached storage systems typically used with xrootd. Maybe
>> > some of you have good suggestions or experiences.
>>
>> Well, I don't know exactly your requirements, but wouldn't it be
>> sufficient to look at the traffic by making an average of the data seen
>> by each client after the file close ?
>>
>> Another (better) way could be to setup XrdMon. Why not ?
>>
>>
>> Fabrizio
>>
>> > For our next upgrade of our Tier2 I would need a benchmark with which I
>> > can measure whether I can satisfy an I/O requirement per worker node
>> > (WN,
>> > or CPU core). This has to be tested while all WNs are reading in
>> > parallel
>> > from all file servers. I just want to assume that the clients from the
>> > WNs are reading in a nicely distributed fashion from the file servers,
>> > e.g. in the case of 10 file servers and 150 WNs, I would assume that in
>> > average 15 WNs are reading at the same time from any file server. But
>> > any
>> > combination of 15 WNs must be able to yield the desired bandwidth.
>> >
>> > Naturally, this benchmark is targeted at mimicking a cluster running
>> > analysis applications.
>> >
>> > A primitive test (but not exactly matching the use case) could be using
>> > netperf or iperf in UDP mode. E.g. the file servers would receive
>> > packets
>> > from the required fraction of worker nodes (The sending intervals and
>> > packet sizes can be set for netperf). One would gradually increase the
>> > sending rate per worker node until UDP packet loss is observed.
>> >
>> > I'm glad for any suggestions.
>> >
>> > Cheers,
>> > Derek
>
> --
> Dr. Derek Feichtinger Tel: +41 56 310 47 33
> AIT Group email: [log in to unmask]
> PSI
> http://people.web.psi.ch/feichtinger
> CH-5232 Villigen PSI
>
>
|