Efficient accumulation of performance statistics in a multi-port network

#The present invention relates generally to large computer networks and, in particular, to accumulating statistics related to the performance of links associated with ports connected to the network.

#In large data network environments, it is important to be able to obtain statistics about the performance of input/output (I/O) operations on the physical network, such as the links which connected ports of different network devices. Statistics of interest can include the number of I/O operations a link can handle (in operations per second); the bandwidth of a link (in megabytes (MB) per second); the average number of concurrent operations using a link during a time period; the average transfer length (in MB/operation); and the average link utilization per operation (in micro-seconds/operation).

#Such statistics may be used in real time to trigger fault procedures if a large variance from a normal value indicates the existence of a possible problem. Statistics may also kept in a log to be referenced during normal maintenance or problem resolution. Typically, statistics may be calculated by a network server, such as an Enterprise Storage Server® (ESS) sold by IBM® and may be maintained by one or more attached host devices. However, due to the large number of links between components in a network, collecting data and sampling the collected data to compute statistics can consume a large amount of valuable network resources. Consequently, it is desirable to provide for more efficient data collection and statistic generation.

#FIG. 1 is a block diagram of a data network in which the present invention may be implemented; and

#FIG. 2 is a block diagram of a multi-port, multi-link storage server.

#FIG. 1 is a block diagram of a data network 100 in which the present invention may be implemented. The network 100 includes one or more host devices 102 and 104, a controller or server 110 and other storage servers 120, 122, 200 with attached data storage devices 121, 123 and 125. Other devices 130 and 132 may also be attached to the network 100. The controller 110 may be an IBM Enterprise Storage Server and includes a processor 112, memory 114 and counters 116 as well as appropriate network interfaces 118. The processor 112 is programmed with instructions stored in the memory 114 for managing I/O operations requested by the host devices 102, 104 as well as for computing network I/O performance statistics. The storage devices 121, 123, 125 may be any type of removable or fixed physical storage including, without limitation, electronic memory (such as RAM or solid state memory), hard disks, RAID arrays, tape cartridges, optical discs and other media. Removable media may be (but need not be) contained with an automated data storage library. As will be appreciated, the counters 116 may be implemented in hardware or software.

#FIG. 2 is a block diagram of the storage server 200. The storage server 200 includes one or more ports 210, 220, 230 and each port may accommodate one or more network links. For example, a port 210 may accommodate three link types such as ECKD 212, PPRC 214 and SCSI 216. Although shown separately in FIG. 2, data transmitted/received over different link types may actually travel over a single physical path to/from the network. Moreover, multiplexing permits all of the links of a port to be used essentially in a simultaneous manner.

#For each link of each port, there are preferably three corresponding counters in the controller 110. A first counter provides an accumulated count of the number of I/O operations processed through the link. A second counter provides the accumulated utilization time (in microseconds or other appropriate unit of time) associated with each I/O operation. And, a third counter provides an accumulated bandwidth comprising the number of bytes transferred by each I/O operation through the link. The utilization time indicates how long a port processor is active with a particular I/O operation and is useful in determining the port's contribution to any delay. Using only the three counters for each port reduces the processing resources required for obtaining performance statistics. From the three counters, a variety of statistics may be computed.