Pool 2 Pool Steering Parameters and Commands ( starting 1.5.2 )

Content


Related PoolManager Command Set

rc set p2p on|off|oncost
rc set stage oncost on|off
rc set fallback oncost on|off
rc set slope <p2p source/destination slope>
rc set max copies <maxNumberOfP2pCopies>
rc set sameHostCopy never|besteffort|notchecked
set costcuts [-<options>=<value> ... ]
#
#   DEPRECATED
#
set costcut <minCut>|* [<maxCut>] # DEPRECATED
#
#  use 'set costcuts -idle=... -p2p=...' instead.
#

Command Set Reference

rc set p2p on|off|oncost

CommandDescription
rc set p2p offUnder no circumstances p2p will be initiated
rc set p2p onP2p transfers will only be used if a dataset resides on a pool which is not allowed to deliver this file to the requesting client. So the file is transferred to another pool first, which, subsequently is allowed to deliver it to the client.
rc set p2p oncostIn addition to the option above, p2p will be used if certain cost conditions apply. (see 'set costcuts').

rc set stage oncost on|off

If stage on cost is enabled and the requested file resides on a pool which can't be used due to cost or configuration conditions and p2p is disabled or can't take place because of configuration or cost constraints, the file will be copied from an HSM to a 'low cost' pool, rather than delivered directly from the pool.

rc set max copies <maxNumberOfP2pCopies>

The PoolManager takes care that there are nver more than <maxNumberOfP2pCopies> of the same file within active pools. If, regarding the settings and the pool cost distribution, a p2p would have been initiated, but the number of actual copies of the file exceeds the confiured value of <maxNumberOfP2pCopies>, the p2p transfer won't take place and the file is taken directly from one of the pools.

rc set fallback oncost on|off

If enabled, the dCache, in case of high load, is allowed to use pools with a low link preference. Otherwise only pools with the highest link preference will be chosen.

rc set sameHostCopy never|besteffort|notchecked

This command determines the relation between pool 2 pool source and destination pools in case both reside on the same host machine. never will rather directly deliver a file from a high cost pool than copy it to another pool if this pool is in the same host machine. notchecked doesn't destingues between pools on the same or on different hosts, and besteffort will do its best to find a source destination pair not being on the same host but will chose it anyway if there is no other choise.

set costcuts [-<options>=<value> ... ]

rc set slope <p2p source/destination slope>

OptionDescription
-idleA pool below this cost is in IDLE mode.
-p2pA pool between cost idle and p2p is in regular mode.
-alertA pool between cost p2p and alert is in pool 2 pool mode. A pool with costs above alert is in excited mode.
Mode of operationCPU Cost interval
FromTo
Idle0<idle>
Regular<idle><p2p>
Excited<p2p><alert>
Alert<alert> ...
A possible setup could be :
   set costcuts -idle=0.2 -p2p=0.6 -alert=1.5
   
Rules
  • The different cost cuts above (idle,p2p,alert) are compared against the pur CPU cost of the particular pool. The CPU cost is NOT multiplied by the cpu cost factor of the set pool decision command prior to comparison.
if(slope=0.0)
  • Pool 2 Pool transfers will only take place FROM pools in Excited mode TO pools in Regular mode.
  • Pools entering Alert mode will no longer be the source of pool to pool transfers.
if(slope>0.0)
  • Pool 2 pool starts if pools are at least in Excited mode.
  • Pool 2 pool will take place as long as
           cost(sourcePool) > slope * cost(destinationPool)
           
In general
  • slope == 0 smoothens pool costs as long as there is a reasonable number of pools in Regular mode. Pool 2 pool totally stops if all pools entered Excited mode.
  • slope > 0 smoothens pool costs independently of their absolute costs.
  • slope >= 1 will lead to chaotic behaviour.

Author : Patrick Fuhrmann patrick.fuhrmann@desy.de (Last Updated : $Date: 2005/04/29 12:38:57 $)