db_io_dnfs_metrics

As you may know, there is some views available since 11g to monitor the dnfs activity:

  • v$dnfs_servers: Shows a table of servers accessed using Direct NFS.
  • v$dnfs_files: Shows a table of files now open with Direct NFS.
  • v$dnfs_channels: Shows a table of open network paths (or channels) to servers for which Direct NFS is providing files.
  • v$dnfs_stats: Shows a table of performance statistics for Direct NFS.

One interesting thing is that the v$dnfs_stats view provides two new columns as of 11.2.0.4:

  • NFS_READBYTES: Number of bytes read from NFS server
  • NFS_WRITEBYTES: Number of bytes written to NFS server

See the oracle documentation here.

Then, by sampling the view we can provide those metrics:

  • Reads/s: Number of read per second.
  • KbyRead/s: Kbytes read per second (as of 11.2.0.4).
  • AvgBy/Read: Average bytes per read (as of 11.2.0.4).
  • Writes/s: Number of Write per second.
  • KbyWrite/s: Kbytes write per second (as of 11.2.0.4).
  • AvgBy/Write: Average bytes per write (as of 11.2.0.4).

To do so, I just created a very simple db_io_dnfs_metrics.pl utility. It basically takes a snapshot each second (default interval) from the gv$dnfs_stats view and computes the delta with the previous snapshot. The utility is RAC aware.

Let’s see the help:

$>./db_io_dnfs_metrics.pl -help

Usage: ./db_io_dnfs_metrics.pl [-interval] [-count] [-inst] [-display] [-sort_field] [-help]

 Default Interval : 1 second.
 Default Count    : Unlimited

  Parameter         Comment                                                           Default
  ---------         -------                                                           -------
  -INST=            ALL - Show all Instance(s)                                        ALL
                    CURRENT - Show Current Instance
  -DISPLAY=         What to display: snap,avg (comma separated list)                  SNAP
  -SORT_FIELD=      reads|writes|iops                                                 NONE

Example: ./db_io_dnfs_metrics.pl
Example: ./db_io_dnfs_metrics.pl  -inst=BDT_1
Example: ./db_io_dnfs_metrics.pl  -sort_field=reads

This is a very simple utility, the options/features are:

  1. You can choose the number of snapshots to display and the time to wait between the snapshots.
  2. In case of RAC, you can choose on which database instance to collect the metrics thanks to the –INST= parameter.
  3. You can display the metrics per snapshot, the average metrics value since the collection began (that is to say since the script has been launched) or both thanks to the –DISPLAY= parameter.
  4. In case of RAC, you can sort the instances based on the number of reads, number of writes, number of IOPS (reads+writes) thanks to the –SORT_FIELD= parameter.

Examples:

Collecting on a single Instance:

$>./db_io_dnfs_metrics.pl
............................
Collecting 1 sec....
............................

......... SNAP TAKEN AT ...................

14:26:18                          Kby       AvgBy/               Kby       AvgBy/
14:26:18   INST         Reads/s   Read/s    Read      Writes/s   Write/s   Write      IOPS       MB/s
14:26:18   ----------   -------   -------   -------   --------   -------   --------   --------   --------
14:26:18   VSBDT        321       2568      8192      0          0         0          321        2.5
............................
Collecting 1 sec....
............................

......... SNAP TAKEN AT ...................

14:26:19                          Kby       AvgBy/               Kby       AvgBy/
14:26:19   INST         Reads/s   Read/s    Read      Writes/s   Write/s   Write      IOPS       MB/s
14:26:19   ----------   -------   -------   -------   --------   -------   --------   --------   --------
14:26:19   VSBDT        320       2560      8192      1          16        16384      321        2.5

Collecting on a RAC database, sorting the Instances by the number of read:

$>./db_io_dnfs_metrics.pl -sort_field=reads
............................
Collecting 1 sec....
............................

......... SNAP TAKEN AT ...................

17:21:21                          Kby       AvgBy/               Kby       AvgBy/
17:21:21   INST         Reads/s   Read/s    Read      Writes/s   Write/s   Write      IOPS       MB/s
17:21:21   ----------   -------   -------   -------   --------   -------   --------   --------   --------
17:21:21   VBDTO_1      175       44536     260599    0          0         0          175        43.5
17:21:21   VBDTO_2      69        2272      33718     0          0         0          69         2.2
............................
Collecting 1 sec....
............................

......... SNAP TAKEN AT ...................

17:21:22                          Kby       AvgBy/               Kby       AvgBy/
17:21:22   INST         Reads/s   Read/s    Read      Writes/s   Write/s   Write      IOPS       MB/s
17:21:22   ----------   -------   -------   -------   --------   -------   --------   --------   --------
17:21:22   VBDTO_2      151       36976     250751    0          0         0          151        36.1
17:21:22   VBDTO_1      131       33408     261143    0          0         0          131        32.6
............................
Collecting 1 sec....
............................

......... SNAP TAKEN AT ...................

17:21:23                          Kby       AvgBy/               Kby       AvgBy/
17:21:23   INST         Reads/s   Read/s    Read      Writes/s   Write/s   Write      IOPS       MB/s
17:21:23   ----------   -------   -------   -------   --------   -------   --------   --------   --------
17:21:23   VBDTO_2      133       33592     258633    0          0         0          133        32.8
17:21:23   VBDTO_1      121       31360     265394    0          0         0          121        30.6

Remarks:

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