ONTAP Discussions

Write I/O Block Size




Does anyone know how to get Write I/O block size for a volume/LUN by way of System Manager, Unified Manager or CLI for a NAS filer?


I would assumne it should be pretty easy within Unified Manager but I'm not finding the data.


Thanks in advance!


Re: Write I/O Block Size


It's much easier via CLI for cDOT. 


If you run this command:
SANCL1::> qos statistics volume characteristics show


You get output for all the volumes in the cluster, just look for Request size that's your IO size.

If you want to know the IO size for specific volume then use the following command:

SANCL1::> qos statistics volume characteristics show -volume v_dmz -vserver san01
Workload          ID       IOPS Throughput     Request Size (IO Size) Read Concurrency
--------------- ------ -------- ---------------- ------------ ---- -----------
     v_dmz        21451   6            3.00KB/s          512B         66%           0

View solution in original post

Re: Write I/O Block Size


Is that only READs? What about writes? Nothing with a timeline?

Re: Write I/O Block Size


Nevermind, I miss read. Thanks for the help!

Re: Write I/O Block Size


statistics volume show has a field for op size. There is also one for statistics lun show. However you can always take the bytes/second divided by # of IOPs.


For example, 21,626,880‬ read byte/second divided by 330 read IOPs would be 65535.


Note: stats volume is limited to 64k because the WAFL file layer does 64k. At the protocol level it gets split up into multiple 64k chunks. You can use stats nfsv3/smb2 or stats lun to get a readout of op size > 64k.


Documentation: https://docs.netapp.com/ontap-9/index.jsp?topic=%2Fcom.netapp.doc.dot-cm-cmpr-950%2FTOC__statistics.html&lang=en

Examples for node shell/7-mode: https://kb.netapp.com/app/answers/answer_view/a_id/1035917/loc/en_US

Note: Documentation is more generic to stats/statistics commands, but should give you an idea.

Let me know if you need more help getting the syntax.

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