assume a small rack of 20 1U/2U dual-quad-cores + 8 disks each. Such a
rack can process: 20 * 8 * 15 = 2.4GB/s (15MB/s ROOT compressed file
reading speed, I/O bound query). Now such a rack would need a switch with a
dual 10GB uplink to get just 2 GB/s in over the network. Now add another
couple of such racks. You would need a disk pool + a lot of 10GB eth
equipment per rack. You still think it scales better than having disks
close to the CPU's?
Fabrizio Furano wrote:
> Hi Pablo,
> that's very interesting, and I agree completely with your conclusion,
> i.e. in most cases the lan data access is more efficient and scales
> better with respect to local disk access. Many times this is not very
> well understood by people, always striving to keep local files at any cost.
> It would be very interesting to have a comparison between the
> performance in proof between a dcache storage and an analogous xrootd
> storage, which is the default solution for that. With the same pool of
> workers of course.
> From what I've understood, dcache uses a read ahead mechanism (at the
> client side), while xrootd uses a scheme which is mixed with informed
> async prefetching.
> Pablo Fernandez ha scritto:
>> Hi all,
>> I would like to share with you some information about my testings of
>> performance in Proof with different storage schemas.
>> I have translated this topic to the Proof Forum since seems to me more
>> Proof-related than just xrootd, I hope you don't mind.
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