Number of streams when using eos cp

Site Administrators
1

Dear Experts,

As you know, there is an option to specify the number of parallel streams when using eos cp as shown below quoted from eos cp --help:

Usage: cp [--async] [--atomic] [--rate=<rate>] [--streams=<n>] [--depth=<d>] [--checksum] [--no-overwrite|-k] [--preserve|-p] [--recursive|-r|-R] [-s|--silent] [-a] [-n] [-S] [-d[=][<lvl>] <src> <dst>
       --streams       : use <#> parallel streams

However it does not affect at all the transfer performance as it increases (tried the number of streams only from 1 to 5 for just testing).

I was just wondering what exactly the number of parallel streams means here and how it runs. Also it would be very grateful to know in which case it is most effective.

Thank you.

Best regards,
Sang-Un

2

Hi Sang-Un,

The --streams option has no effect since there is no actual implementation behind it … The xrootd client is capable of utilizing the full bandwidth of the network connection with only one stream if enough data is available. Therefore, there should be no considerable modification in performance w/o streams.

Just as a test you can use the xrdcp command which has the --streams option, if you want to compare the performance.

Cheers,
Elvin