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Support #18789

PNFS transfer speed

Added by Arthur Kreymer almost 2 years ago. Updated almost 2 years ago.

Status:
New
Priority:
Immediate
Start date:
01/24/2018
Due date:
01/26/2018
% Done:

20%

Estimated time:
2.00 h
Duration: 3

Description

Investigate and address slow PNFS transfer speeds reported recently.

History

#1 Updated by Arthur Kreymer almost 2 years ago

Date: Mon, 22 Jan 2018 10:13:05 -0600
From: Simon De Rijck <>

ifdh cp
/pnfs/minos/scratch/users/simon217/SterileTwoDetectorFit/FitFiles/Combined/fluc-1-1-normal-lower-index-16-freeDm232-0-freeTh23-0-statsOnly-0-parity-0-statsFluct-0-poisson-0-systsFluct-1-covFluct-0-CovMtx_FHC_LEME_LoE_enuni_comb_s11111111_beam.root
/pnfs/minos/persistent/users/simon217/SterileTwoDetectorFit/FitFiles/Combined/fluc-1-1-normal-lower-index-16-freeDm232-0-freeTh23-0-statsOnly-0-parity-0-statsFluct-0-poisson-0-systsFluct-1-covFluct-0-CovMtx_FHC_LEME_LoE_enuni_comb_s11111111_beam.root

#2 Updated by Arthur Kreymer almost 2 years ago

  • % Done changed from 10 to 20

The problem for these files is in the file overheads.

There are 3618 small files in
/pnfs/minos/scratch/users/simon217/SterileTwoDetectorFit/FitFiles/Combined
Sizes range from 40 KB to 200 KB.
dCache is pretty inefficient at handling such small files.

A typical copy takes 4 seconds. That's 4 hours to copy the directory.

PIN=/pnfs/minos/scratch/users/simon217/SterileTwoDetectorFit/FitFiles/Combined/
POU=/pnfs/minos/persistent/users/kreymer/TEST/RATE

FILE=`ls ${PIN} | head -1`

FIN=${PIN}/${FILE}
FOU=${POU}/${FILE}

time ifdh cp ${FIN} ${FOU}

real    0m4.269s
user    0m0.376s
sys    0m0.165s
In this case, a direct file system dd is much faster
dd if=${FIN} of=${FOU} bs=10M
0+1 records in
0+1 records out
154794 bytes (155 kB) copied, 0.533082 s, 290 kB/s


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