EVA Read Miss Req/s

 
bernikm
Occasional Advisor

EVA Read Miss Req/s

Hi

 

We are dealing with a disk performance impact on VM running on Hyper-V R2 server with EVA 4400.

I noticed that two VM are generating very high Read Miss Req/s.

 

Total Read Miss Req/s on datastore with 8x300GB FC 15k disks is 334

Total Read Miss Req/s on datastore with 10x400GB FC 10k disks is 150

 

I'm new with an EVA storage, so are these numbers normal or not ?

 

   Disk Total  Total Average Total  Total Average Total  Total Average  Total  Total    Total Ctlr Node
  Group  Read   Read    Read  Read   Read    Read Write  Write   Write  Flush Mirror Prefetch
          Hit    Hit     Hit  Miss   Miss    Miss Req/s   MB/s Latency   MB/s   MB/s     MB/s
        Req/s   MB/s Latency Req/s   MB/s Latency                 (ms)
                       (ms)                 (ms)
------ ----- ------ ------- ----- ------ ------- ----- ------ ------- ------ ------ -------- ---- -------------------
     01     0   0.00     0.0     0   0.00     0.0     2   0.00     0.1   0.00   0.00     0.00 C09V 5001-4380-025D-0CD0
     01   107   6.37     0.5   334  18.15     2.0     2   0.03     0.2   0.00   0.03     8.46 R026 5001-4380-025D-0CD0
Default     0   0.00     0.0     0   0.00     0.0    40   0.20     0.2   0.00   0.20     0.00 C09V 5001-4380-025D-0CD0
Default    39   0.12     0.0   149   1.80     1.2    39   0.15     0.1   0.00   0.15     0.12 R026 5001-4380-025D-0CD0

1 REPLY 1
Jan Soska
Honored Contributor

Re: EVA Read Miss Req/s

Hello,

read miss shows that data needed by host were not in cache. This is absolutelly normal in random read scenario. There is predictive algoritm which read ahead, but can not predict random reads... :)

Test your EVA with sequential read and see the diference - almost 100% read hit, very low read miss counts.

 

Much more importand counter is read / write latency. Bellow 20-25ms - you are all right, above - there is i/o shortage - usually not enough disk spindles...

 

jan