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Understanding OnCommand Reported Disk Space

So my boss gives me the task to produce some info on the disk space we have in our DS2246 and our DS4246 devices since they have been around a while and things need reviewing.  So I jump into OnCommand and start looking around. 

 

I am confused with what Storage -> Aggregates is showing me.  It reports Total Space 13.24 TB with a 22 Disk Count.

 

I have 24 disk at 900 GB SAS each with 12 in rg0 and 12 in rg1.  Loss two as spares.  I also have the 2 parity and 2 dparity 1 each in rg0 and rg1.  So I get the 22 disk if we include the parity disk, which matches the above Disk Count of 22.  But the Total Space is throwing me.  Shouldn't it be around 18 TB or so minus the overhead for various reasons.  Even 17.xx TB or 16.XX TB, but 13.24.

 

The three volumes on this aggr0 are 714.14GB, 3 TB, and 8 TB yields 11.714 TB, but the Storage -> Aggregates value for Used Space is 10.02 TB.

 

Then if I look at Storage -> Disks and the values for Effective Size I get even more unsure.  836.91 GB x 22 = 18.412 TB and remove the parity disk for actual space for data the results would be 836.91 x 18 = 15.064 TB which is not even near 11.714 or 10.02 though I can understand if this ... sort of.

 

And in lite of the fact that I am using RAID-DP i was expecting a "half-the-space" value somewhere since I thought rg0 was RAIDing its contents to rg1.

 

Is it better to use "df" at the command line to get the info I am looking for? 

 

Thank you all for your input and kindness to your more confused and spacially challenged members. Smiley Happy

Re: Understanding OnCommand Reported Disk Space

Hi

 

If you just need to do this once I would say go with df command but if you want to schedule this report on a time basis then do in in OCI . anyway I need to know how you making your report to tell wherethe issue is because there are diffrent ways to get the size like ( RAW capacity , Capacity , Projected and etc ) so each one of these return diffrent numbers.

 

Re: Understanding OnCommand Reported Disk Space

Hi,

 

Out of 24 disks, 2 are allocated for spare. so 22 disk are remaining, out of 22 disks 4 will be allocated for partity (as you have 2 raid groups) 18 remaining.

10% of space will be allocated for WAFL so you will get usable space around 15TB for 900GB SAS (18) disk drives.

5% aggregate snap reserve, 20% volume snap reserve (default- you can change this value depends upon your environment standards).

probably you may find below links as useful

http://community.netapp.com/t5/Data-ONTAP-Discussions/NetApp-Usable-Space-Calculator/td-p/76807

http://wintelguy.com/netappcalc2.pl