Information on cdm probe inode calculation for zfs disk for Solaris

Document ID : KB000015901
Last Modified Date : 14/02/2018
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Question:

How cdm probe calculates inodes for zfs disk?

Environment:
UIM 8.5xcdm 5.x, 6.xSolaris
Answer:

On Solaris platform cdm probe uses system call statvfs  . 

This call provides values of f_files and f_ffree 

As far as calculation is concerned , 

iInodeMax = f_files

iInodeUsed = f_files - f_ffree              

QOS_INODE_USAGE_PERC = (iInodeUsed * 100) / InodeMax

 

Below is response from Oracle regarding the values we’re using in CDM probe for calculating INODE data,

zfs.png

FAQ

  • Do you mean to say that zfs disk are using inodes and should be calculated for zfs disks ?

In case of ZFS file system there is no preallocated files unlike other file systems , so there is no fixed value. These values change dynamically . So in case of ZFS , the value is maximum that could fit in f_files .  

For  ZFS file system though these values can change with increase in inode usage ,at a particular instance these value makes sense.

For clients who do not want to see INODE metrics , can disable it as it is configurable. Can manually uncheck the the inode QOS and threshold metrics ( this is by default unchecked ) in cdm probe

To summarize we cannot say that ZFS is not supporting inode information . The difference is , values are not fixed/predefined in ZFS’s case .

When needed (usage about to reach maximum limit) , maximum usage limit is increased dynamically . so they shows maximum value that can be fit in f_files .So it is up to individual client whether they are interested in these values or not.