RRDs stats for SR object

[olivierlambert]

FYI, the SR uuid is on the format:

"AVERAGE:host:<hostUUID>:<statname>_<SR partial UUID>"

With partial UUID the first group of UUID (first 8 chars)

Example:

"AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:inflight_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:iowait_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:iops_total_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:iops_write_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:iops_read_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:io_throughput_total_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:io_throughput_write_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:io_throughput_read_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:write_latency_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:read_latency_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:write_e6616eb6",
            "AVERAGE:host:77b3f6ad-020b-4e48-b090-74b2a26c4f69:read_e6616eb6",

I'd like to have:

• IOPS (read/write)
• IO throughput (read/write)
• Latency (read/write)
• IOwait