topic Re: Can I calculate the amount of data being written to from OCUM? in ONTAP Discussions

Can I calculate the amount of data being written to from OCUM?

netappmagic — Wed, 04 Jun 2025 11:18:54 GMT

I have a NFS volume and used for Oracle backups, to calculate the amount of data being written to the volume by using NetApp tool, I pulled out the MBps graph in OCUM, based on the starting and ending time, and average MBps, I got the total amount = length x avg MBps.

Is there any problems with this method to estimate the total amount?

Re: Can I calculate the amount of data being written to from OCUM?

Ontapforrum — Tue, 18 Feb 2020 16:09:41 GMT

Hi,

Is this just for test exercise ? Taking avg resource for calculations are fine as far as performance metrics are concerned such as IOPS and throughput but I wouldn't rely on it for 'used-space'. I suggest take the estimated figure from your calculation and compare it with the actual used space (see the deviation) from the console output or based on the OCUM. In fact, OCUM also shows you used-data space but it's not real-time, data is pulled based on the polled interval.

::> volume show-space -vserver <vserver> -volume <volume>

In the output, look at this field for accurate measure of the user-data (excluding all meta-datas)
User Data: xx

Hope I understood your query.

Thanks!

Re: Can I calculate the amount of data being written to from OCUM?

netappmagic — Tue, 18 Feb 2020 17:28:00 GMT

Thanks!

I am not asking how much space been used, but how much been written to the NFS volume during this period of the time? because there are a lot of overwritten data, and also they keep 1 month worth of data.

Again, my method can give us a rough idea?

Re: Can I calculate the amount of data being written to from OCUM?

Ontapforrum — Wed, 19 Feb 2020 08:54:33 GMT

Your query is clearer now. That's perfectly reasonable method to establish amount of data written to volume for a given time. Now, how much if that written data is actually new blocks could be guessed looking at the snap delta.

Re: Can I calculate the amount of data being written to from OCUM?

paul_stejskal — Thu, 20 Feb 2020 17:00:01 GMT

If the database isn't changing a lot and you want to reduce the amount of change rate, you can separate the tempdb. Of course, you may want a single LUN/volume for ease of troubleshooting.