▁Best ▁Client ▁– ▁Each ▁node ▁records ▁number ▁of ▁requests ▁per ▁file ▁received ▁during ▁a ▁pres et ▁time ▁interval ; ▁if ▁the ▁request ▁number ▁exceed s ▁the ▁set ▁threshold ▁for ▁a ▁file ▁a ▁rep lica ▁is ▁created ▁on ▁the ▁best ▁client , ▁one ▁that ▁requested ▁the ▁file ▁the ▁most ; ▁st ale ▁rep lic as ▁are ▁removed ▁based ▁on ▁another ▁algorithm . ▁▁ ▁C asc ading ▁– ▁Is ▁used ▁in ▁a ▁hier arch ical ▁node ▁structure ▁where ▁requests ▁per ▁file ▁received ▁during ▁a ▁pres et ▁time ▁interval ▁is ▁compared ▁against ▁a ▁threshold . ▁If ▁the ▁threshold ▁is ▁exceed ed ▁a ▁rep lica ▁is ▁created ▁at ▁the ▁first ▁tier ▁down ▁from ▁the ▁root , ▁if ▁the ▁threshold ▁is ▁exceed ed ▁again ▁a ▁rep lica ▁is ▁added ▁to ▁the ▁next ▁tier ▁down ▁and ▁so ▁on ▁like ▁a ▁water fall ▁effect ▁until ▁a ▁rep lica ▁is ▁placed ▁at ▁the ▁client ▁itself . ▁ ▁P lain ▁C aching ▁– ▁If ▁the ▁client ▁requests ▁a ▁file ▁it ▁is ▁stored ▁as ▁a ▁copy ▁on ▁the ▁client . ▁ ▁C aching ▁plus ▁C asc ading ▁– ▁Com b ines ▁two ▁strateg ies ▁of ▁caching ▁and ▁cas c ading . ▁ ▁Fast ▁Sp read ▁– ▁Also ▁used ▁in ▁a ▁hier arch ical ▁node ▁structure ▁this ▁strategy ▁automatically ▁popul ates ▁all ▁nodes ▁in ▁the ▁path ▁of ▁the ▁client ▁that ▁requests ▁a ▁file . ▁ ▁Task s ▁sched uling ▁and ▁resource ▁allocation ▁Such ▁characteristics ▁of ▁the ▁data ▁grid ▁systems ▁as ▁large ▁scale ▁and ▁heter ogene ity ▁require ▁specific ▁methods ▁of ▁tasks ▁sched uling ▁and