Documentation/op-guide: explain auto-compaction logic
Documentation/op-guide: explain auto-compaction logic

Signed-off-by: Gyuho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

dannysauer/etcd,mkumatag/etcd,mkumatag/etcd,sinsharat/etcd,joshix/etcd,mqliang/etcd,ajityagaty/etcd,vimalk78/etcd,dannysauer/etcd,lorneli/etcd,rnaveiras/etcd,gyuho/etcd,xiang90/etcd,glevand/coreos--etcd,rnaveiras/etcd,rnaveiras/etcd,fanminshi/etcd,mqliang/etcd,vimalk78/etcd,cockroachdb/etcd,gyuho/etcd,li-ang/etcd,coreos/etcd,sebrandon1/etcd,fanminshi/etcd,bdarnell/etcd,lorneli/etcd,glevand/coreos--etcd,ajityagaty/etcd,bdarnell/etcd,ajityagaty/etcd,li-ang/etcd,etcd-io/etcd,sebrandon1/etcd,etcd-io/etcd,mqliang/etcd,cockroachdb/etcd,coreos/etcd,joshix/etcd,mkumatag/etcd,sinsharat/etcd,etcd-io/etcd,xiang90/etcd