Hey Chris,
there is a pretty old paper called "Useful Constants for the Oracle Performance
Analyst" by Cary Millsap and Jeff Holt which mentions 10 ms per single-block
disk read (PIO) as max. tolerated latency per event.
However you usually see much lower latency per event (basically what you have
expected) as storage sub-systems (even the cheaper mid-range ones) have
read/write caches to support the spinning disks. So I would not consider 10 ms
as "normal" as long as I am not sure about the root cause of it.
Best Regards
Stefan Koehler
Independent Oracle performance consultant and researcher
Website: http://www.soocs.de
Twitter: @OracleSK
Chris Stephens <cstephens16@xxxxxxxxx> hat am 9. Mai 2018 um 15:48--
geschrieben:
thanks for everyone's input on this. the 10ms I/O times are relatively
constant on this disk group. we were just looking to make sure those disks
are performing as expected. I have always considered 5ms single block I/O
response times for spinning disks as typical and when I saw 10ms I thought
maybe something was up. not sure how i got that 5ms number stuck in my head.
Luckily we also have a disk group on SSD's that performs far better.
thanks again everyone. even you and your criticisms mladen. :)
