Verifying the VxFS cache area and monitoring the caching (writeback mode)


Verifying the VxFS cache area and monitoring the caching (writeback mode)
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After the SmartIO feature is configured, you can verify that the cache area is present and that caching is occurring.

For a VxFS cache area, the sfcache list command shows the caching mode for the file or directory. If the mode is not explicitly set, the file or directory inherits the caching mode of the mount point. If the mode is explicitly set for a file or directory, that value persists across remounts. The displayed caching mode may differ from the mode that is enabled for the mount point. The writeback mode is not enabled unless the file system is mounted in writeback mode. If a file or directory is set to writeback mode, but the file system is mounted in another mode, the file or directory inherits the caching mode of the mount point.

To verify and monitor the cache area

To display information about the cache areas on the system.
```
# sfcache list
```
For example, a single-node VxFS cache area displays output as follows:
```
NAME          TYPE SIZE  ASSOC-TYPE  STATE   DEVICE 
sfcachearea_2 VxFS 9.96g AUTO        ONLINE  ssd0_0
```
For a cluster file system with writeback enabled, if you issue the sfcache list command just after you mount with writeback enabled (and before any read caching has happened), the output shows the space used in cache as 1.0 GB. Cache reflection is configured, with a local log and a remote log that each have a log size of 512 MB.

To display information about a specific cache area:

# sfcache list sfcachearea_2

Cachearea: sfcachearea_2
Assoc Type: AUTO
Type: VxFS
Size: 9.96g
State: ONLINE
Layout: CONCAT
Number of Columns: 0

/dev/vx/dsk/cachedg/ssdvol:
FSUUID                                                  SIZE  MODE       MOUNTPOINT
5dfe4a52805b0b003c7600002cde6d2ce70300005dfe4a52    551.0 MB  writeback  /mnt1
5efe4a52eb76000041760000a0dec33fe70300005efe4a52     39.0 MB  read       /mnt2
5efe4a524a86050046760000b485af64e70300005efe4a52    551.0 MB  writeback  /mnt3

The output displays information about the cache configuration and attributes.

See Displaying information about a cache area.

To display information about a specific file system:

# sfcache list /mnt1

/mnt1:
READ CACHE    WRITEBACK    MODE       PINNED  NAME
   39.0 MB         0 KB    writeback  yes     /mnt1/dir
   39.0 MB         0 KB    writeback  yes     /mnt1

To see statistics on the cache usage, use the following command:

# sfcache stat sfcachearea_2

TYPE: VxFS
NAME: sfcachearea_2
               Cache Size:    9.97 GB
        Cache Utilization:   1.133 GB (11.37 %)
 File Systems Using Cache:       3
Writeback Cache Use Limit:       8 GB
  Writeback Flush Timelag:      10 s

Read Cache                                Writeback
Hit Ratio   Data Read  Data Written   Hit Ratio   Data Written

Total:
   0.00 %       0 KB       195.0 MB   100.00 %         78.0 MB

/mnt1:
   0.00 %       0 KB        78.0 MB   100.00 %         39.0 MB

/mnt2:
   0.00 %       0 KB        39.0 MB     0.00 %            0 KB

/mnt3:
   0.00 %       0 KB        78.0 MB   100.00 %         39.0 MB

The output displays statistics for the cached data.

See Viewing the SmartIO cache statistics .

To see statistics on cache usage for a particular file system, use the following command:

# sfcache stat /mnt1

Cache Size:    9.97 GB
Cache Utilization:   551.0 MB ( 5.40 %)

Read Cache                                Writeback
Hit Ratio    Data Read    Data Written    Hit Ratio    Data Written

/mnt1:
   0.00 %         0 KB         78.0 MB     100.00 %         39.0 MB

Check the syslog to verify whether writeback mode caching is enabled.
You should see a line such as the following in the syslog:
```
vxfs: msgcnt 4 writeback caching is enabled for /dev/vx/dsk/testdg/vol1
```
If writeback mode caching is disabled for a particular file system, you would see a line such as the following in the syslog:
```
vxfs: msgcnt 9 writeback caching is disabled for /dev/vx/dsk/testdg/vol1
```

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