Re: Very High Rate Continous Transfer

In article <ASSY525711F330@xxxxxxxxxxxxx>,
Stephen Maudsley <news2@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
><jim_nospam_beasley@xxxxxxxxx> wrote in message
>news:1121528669.995816.282650@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> I am looking into what it will take to support continuous (not burst)
>> 160 to 200 MBytes/sec transfer to disk. What types of drives and how
>> would they be configured as an array (or multiple arrays)?
>>
>> What type of processor and bus architecture would be appropriate? Data
>> will be from a capture memory that is shared between the processor and
>> the capture electronics. So memory bandwidth will be at least 320 to
>> 400 MBytes/sec.
>
>Might be worth looking for articles and papers from CERN - they've been
>doing this sort of stuff for years and used to publishe papers on the
>computing architectures.

Being a retired high-energy physicist (and former CERN collaborator)
myself ...

Yes, it would be a good idea to start there, and read their stuff. A
good starting point is to look for the web presence of the "CERN
OpenLab", and read what is posted there.

But the original poster's situation and CERN are in different leagues.
I've recently seen a ~1 GByte/sec test running at CERN, sustained for
a whole week. But it required O(100) computers, massive networking
gear, and many hundred disk drives, with some of the finer software
and hardware products from industry thrown into the mix. It also
consumed all told probably a dozen people (both from CERN and from
industry) for a year to set up, and the hardware cost should be
measured in units of M$.

The other thing to remember is that to CERN, the data storage problem
(even though it is massive) is a small part of their overall mission.
Anyone who spends ~10 billion $ on building an accelerator, about the
same on the physics experiments, and a few billion $ a year on
operation and support, has a strong incentive to build a reliable and
fast data storage system, because loss of data would have huge
economic costs.

I very much doubt that the original poster's system will reach this
scale; still, stealing some good ideas there is a good plan.

Another thing to remember from the CERN experience: Just because the
system can do a certain speed (say 400 MB/sec) once, doesn't mean at
all that it can do so sustained. Things go wrong all the time
(guaranteed to happen in a large system, which typically even involves
a few humans, which are about as unreliable as disk drives, and nobody
has invented RAID for sys admins yet). The real test is not to do 400
MB/sec for 10 seconds, but do so sustained 24x7 for a month. This is
much much harder.

--
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