does reduce > copy (at 0.52 MB/s) means network or other IO problem?

[Vitaliy Semochkin]

Hello,

I often see reduce > copy (at 0.52 MB/s)  phase with such speed.
Despite in my cluster all 5 nodes are in same rack.
Does it mean any network or other IO problems, or other reasons can
cause such slow speed?

Thanks in Advance,
Vitaliy S