Exam 70-765 topic 4 question 18 discussion

Actual exam question from Microsoft's 70-765

Question #: 18
Topic #: 4

You have Microsoft SQL server on a Microsoft Azure virtual machine. The virtual machine has 200 GB of data.
User report a slow response time when querying the database.
You need to identify whether the storage subsystem causes the performance issue.
Which performance monitor counter should you view?

A. Data sec/Write
B. Avg.disk Read Queue Length
C. % Disk Read Time
D. Disk sec/Read

Show Suggested Answer

Suggested Answer: B 🗳️

by DudeHere at April 12, 2020, 10:52 a.m.

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Cococo

4 years, 8 months ago

Looks like D, check the Exam Reference book. B is not valid in case of shared space like SAN or VM - https://www.sqlshack.com/bi-performance-counter-avg-disk-queue-length/

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MelKr

5 years, 1 month ago

Actually, disk_queue_length by itself does not give any relevant information only that the disk is busy but not how busy actually. We would need to know the number of physical disks to judge if the value is too high. You should measuer "Disk sec/Read" which is independent of underlying hardware and gives you a good measure for IO-performance. see: https://www.mssqltips.com/sqlservertip/2460/perfmon-counters-to-identify-sql-server-disk-bottlenecks/

upvoted 3 times

jolsca

4 years, 10 months ago

Is correct D

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Slava_bcd81

4 years, 10 months ago

B, If disk have a queue it means it slows down the system, no options

upvoted 1 times

Slava_bcd81

4 years, 10 months ago

If where was kind of "I/O priority setup" that would give SQL Server processes high I/O priority - that would mitigate that issue, but I never heard about such option

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DudeHere

5 years, 3 months ago

B. https://www.sciencedirect.com/topics/computer-science/disk-queue-length

upvoted 3 times

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