Hp XP Performance Advisor Software Instrukcja Użytkownika Pobierz pdf (Strona 59)

C Relationship between LDEV I/O response

time and Write ratio

We cannot establish a relationship between the LDEV I/O response time and Write ratio because:

• LDEV I/O response time is dependent on both front-end reads and front-end writes.

• Write ratio provides only the write percentage in the I/Os.

NOTE:

The LDEV I/O response time shown by XPWatch is the average I/O response time measured in

milliseconds (that is, both reads and writes together are responsible for variations in this value).

The LDEV response time in XPWatch is calculated using the formula:

(front-end read response time over the collection interval * front-end reads + front-end writes * front-end

write response time over the collection interval) / (total front-end I/O)

where:

• front-end reads = front-end random reads + front-end sequential reads

• front-end writes = front-end random writes + front-end sequential writes

• Total front-end I/O = front-end reads + front-end writes

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Hp XP Performance Advisor Software Instrukcja Użytkownika Strona 59