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Full Discussion: Zfs - what does atime update?
Operating Systems Solaris Zfs - what does atime update? Post 302954571 by jabberwocky on Wednesday 9th of September 2015 04:49:02 AM
Old 09-09-2015
Zfs - what does atime update?
It is widely documented that on zfs atime updates the access time on zfs.
Where is the access time updated on Solaris 11.2?

If I create file atimetest.txt under rpool/export/home:

Code:
# zfs list rpool/export/home
NAME                USED  AVAIL  REFER  MOUNTPOINT
rpool/export/home  13.3G  21.0G  13.3G  /export/home
#

Code:
# ls -lt /export/home/atimetest.txt
-rw-r--r--   1 root     root          15 Sep  9 09:31 /export/home/atimetest.txt
# cat /export/home/atimetest.txt
this is a test
#

The atime is set to on, so I set it to off:
Code:
# zfs get atime rpool/export/home
NAME               PROPERTY  VALUE  SOURCE
rpool/export/home  atime     on     default
# zfs set atime=off rpool/export/home
# zfs get atime rpool/export/home
NAME               PROPERTY  VALUE  SOURCE
rpool/export/home  atime     off    local
#

I then check the time, run ls -ld against the directory, run ls -tl against the file:
Code:
# date
Wednesday,  9 September 2015 09:39:10 BST
# ls -ld /export/home
drwxr-xr-x  11 root     root          12 Sep  9 09:31 /export/home
# ls -lt /export/home/atimetest.txt
-rw-r--r--   1 root     root          15 Sep  9 09:31 /export/home/atimetest.txt
#

Then cat the file from /:
Code:
# pwd
/
# cat /export/home/atimetest.txt
this is a test
#

Checking the directory with ls -ld and checking the file with ls -lt shows no update for the access time:
Code:
# ls -ld /export/home
drwxr-xr-x  11 root     root          12 Sep  9 09:31 /export/home
# ls -lt /export/home/atimetest.txt
-rw-r--r--   1 root     root          15 Sep  9 09:31 /export/home/atimetest.txt
#

So, where is the access time updated?
I can see the setting of atime=off in zpool history:
Code:
2015-09-09.09:36:17 zfs set atime=off rpool/export/home

but no update for access time.
I'd like to set atime=off for zfs on application servers, but would like a before and after image to access the change.
This behaviour is replicated on both solaris 10 and 11 x86.
 

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