UCD-DISKIO-MIB
UCD-DISKIO-MIB is used to provide per-block device read/write statistics on UNIX-like hosts.
We maintain a database table containing a list of devices and their descriptions and indexes.
UCD-DISKIO-MIB::diskIOIndex.25 = INTEGER: 25 UCD-DISKIO-MIB::diskIODevice.25 = STRING: sda UCD-DISKIO-MIB::diskIONRead.25 = Counter32: 2243373056 UCD-DISKIO-MIB::diskIONWritten.25 = Counter32: 2692804608 UCD-DISKIO-MIB::diskIOReads.25 = Counter32: 14971725 UCD-DISKIO-MIB::diskIOWrites.25 = Counter32: 226097642 UCD-DISKIO-MIB::diskIONReadX.25 = Counter64: 869826766848 UCD-DISKIO-MIB::diskIONWrittenX.25 = Counter64: 2244665733120
We graph both read/write operations per second via diskIOReads/diskIOWrites and read/write bytes per second via diskIONRead/diskIONWritten. We use the 64-bit values instead if they're present.
Graphs from this module are shown in "Disk I/O" under "Health" global and device sections.

