Dell PowerVault ME4 Series Storage System Administrator’s Guide

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Historical performance graphs

The following table describes the graphs of historical statistics that are available for each component type. In the graphs, measurement units are automatically scaled to best represent the sample data within the page space.

Table 1. Historical performance
System component	Graph	Description
Disk, group, pool, tier	Total IOPS	Total number of read and write operations per second since the last sampling time.
Disk, group, pool, tier	Read IOPS	Number of read operations per second since the last sampling time.
Disk, group, pool, tier	Write IOPS	Number of write operations per second since the last sampling time.
Disk, group, pool, tier	Data Throughput	Overall rate at which data was read and written since the last sampling time.
Disk, group, pool, tier	Read Throughput	Rate at which data was read since the last sampling time.
Disk, group, pool, tier	Write Throughput	Rate at which data was written since the last sampling time.
Disk, group, pool, tier	Total I/Os	Number of read and write operations since the last sampling time.
Disk, group, pool, tier	Number of Reads	Number of read operations since the last sampling time.
Disk, group, pool, tier	Number of Writes	Number of write operations since the last sampling time.
Disk, group, pool, tier	Data Transferred	Total amount of data read and written since the last sampling time.
Disk, group, pool, tier	Data Read	Amount of data read since the last sampling time.
Disk, group, pool, tier	Data Written	Amount of data written since the last sampling time.
Disk, group	Average Response Time	Average response time for reads and writes since the last sampling time.
Disk, group	Average Read Response Time	Average response time for reads since the last sampling time.
Disk, group	Average Write Response Time	Average response time for writes since the last sampling time.
Disk, group	Average I/O Size	Average size of reads and writes since the last sampling time.
Disk, group	Average Read I/O Size	Average size of reads since the last sampling time.
Disk, group	Average Write I/O Size	Average size of writes since the last sampling time.
Disk, group	Number of Disk Errors	Number of disk errors since the last sampling time.
Disk, group	Queue Depth	Average number of pending I/O operations being serviced since the last sampling time. This value represents periods of activity only and excludes periods of inactivity.
Pool, tier	Number of Allocated Pages	Number of 4-MB pages allocated to volumes, based on writes to those volumes. Creating a volume does not cause any allocations. Pages are allocated as data is written.
Tier	Number of Page Moves In	Number of pages moved into this tier from a different tier.
Tier	Number of Page Moves Out	Number of pages moved out of this tier to other tiers.
Tier	Number of Page Rebalances	Number of pages moved between disk groups in this tier to automatically load balance.
Tier	Number of Initial Allocations	Number of pages that are allocated as a result of host writes. This number does not include pages allocated as a result of background tiering page movement. (Tiering moves pages from one tier to another, so one tier will see a page deallocated, while another tier will show pages allocated; these background moves are not considered “initial allocations.”)
Tier	Number of Unmaps	Number of 4-MB pages that are automatically reclaimed and deallocated because they are empty (they contain only zeroes for data).
Tier	Number of RFC Copies	Number of 4-MB pages copied from spinning disks to SSD read cache (read flash cache).
Tier	Number of Zero-Pages Reclaimed	Number of empty (zero-filled) pages that were reclaimed during this sample period.