If all the lines have different numbers of fields, then you can match against an array of patterns. Also, I would use dissect to parse the fixed format prefix to the messages.
dissect { mapping => { "message" => "%{[@metadata][timestamp]} %{+[@metadata][timestamp]} %{hostname} %{[@metadata][restOfLine]}" } }
date { match => [ "[@metadata][timestamp]", "yyyy-MM-dd HH:mm:ss" ] }
grok {
match => {
"[@metadata][restOfLine]" => [
"^%{WORD:monitor} %{NUMBER:node} %{NUMBER:rdaccesses:float} %{NUMBER:rdhit:float} \s* %{NUMBER:wraccesses:float} %{NUMBER:wrhit:float} %{NUMBER:free:float} %{NUMBER:clean:float} %{NUMBER:write1:float} %{NUMBER:writen:float} %{NUMBER:wrtsched:float} %{NUMBER:writing:float} %{NUMBER:dcowpend:float} %{NUMBER:dcowproc:float} %{NUMBER:cfcdirtyt1:float} %{NUMBER:cfcdirtyt2:float} %{NUMBER:cfcdirtyt3:float} %{NUMBER:cfcdirtyt4:float}\s+%{NUMBER:delackt1:float} %{NUMBER:delackt2:float} %{NUMBER:delackt3:float} %{NUMBER:delackt4:float}$",
"^%{WORD:monitor} %{NOTSPACE:volume} %{NUMBER:admrsvd:float} %{NUMBER:admused:float} %{NUMBER:snaprsvd:float} %{NUMBER:snapused:float} %{NUMBER:usrrsvd:float} %{NUMBER:usrused:float} %{NUMBER:vsize:float}$",
"^%{WORD:monitor} %{WORD:tier} %{NUMBER:ndisks:float} %{NUMBER:size:float} %{NUMBER:volume:float} %{NUMBER:spare:float} %{NUMBER:free:float} %{NUMBER:unavail:float} %{NUMBER:failed:float}$",
"^%{WORD:monitor} %{NOTSPACE:volume} %{NUMBER:iops:float} %{NUMBER:kbps:float} %{NUMBER:service_times:float} %{NUMBER:queue_length:float}$",
"^%{WORD:monitor} %{NUMBER:node} %{NUMBER:user:float} %{NUMBER:sys:float} %{NUMBER:idle:float}$"
]
}
}