EVS Concepts

**Table 1** EVS concepts
Concept	Description
IOPS	Number of read/write operations performed by an EVS disk per second
Throughput	Amount of data read from and written into an EVS disk per second
Read/write I/O latency	Minimum interval between two consecutive read/write operations of an EVS disk
Burst capability	The burst capability allows the IOPS of a small-capacity disk to reach the disk IOPS burst limit, which can surpass the disk IOPS limit within a certain period of time.
VBD	A device type of EVS disks. VBD EVS disks only support basic SCSI read/write commands.
SCSI	A device type of EVS disks. SCSI EVS disks support transparent SCSI command transmission and allow the server OS to directly access the underlying storage media.