should TRIM be working on my ZFS L2ARC devices?

[Steven Hartland]

----- Original Message ----- 
From: "Dan Mack" <mack at macktronics.com>
To: "Steven Hartland" <killing at multiplay.co.uk>
Cc: <current at freebsd.org>
Sent: Saturday, June 08, 2013 6:38 PM
Subject: Re: should TRIM be working on my ZFS L2ARC devices?


> On Sat, 8 Jun 2013, Steven Hartland wrote:
> 
> <snip>
>>> Does the Vertex 4 and Intel 520 not work with TRIM on FreeBSD or is 
>>> something else going on here?
>>
>> Connected to an controller which supports BIO_DELETE yes they
>> should.
>>
>> Check with:
>> camcontrol identify ada0
> 
> Feature                      Support  Enabled   Value           Vendor
> read ahead                     no yes
> write cache                    yes yes
> flush cache                    yes yes
> overlap                        no
> Tagged Command Queuing (TCQ)   no no
> Native Command Queuing (NCQ)   yes 32 tags
> SMART                          yes yes
> microcode download             yes yes
> security                       yes no
> power management               yes yes
> advanced power management      no no
> automatic acoustic management  no no
> media status notification      no no
> power-up in Standby            no no
> write-read-verify              yes yes 0/0x0
> unload                         no no
> free-fall                      no no
> Data Set Management (DSM/TRIM) yes
> DSM - max 512byte blocks       yes              16
> DSM - deterministic read       no
> Host Protected Area (HPA)      yes      no      250069680/250069680
> HPA - Security                 no
> 
>> camcontrol identify ada1
> 
> Feature                      Support  Enabled   Value           Vendor
> read ahead                     yes yes
> write cache                    yes yes
> flush cache                    yes yes
> overlap                        no
> Tagged Command Queuing (TCQ)   no no
> Native Command Queuing (NCQ)   yes 32 tags
> SMART                          yes yes
> microcode download             yes yes
> security                       yes no
> power management               yes yes
> advanced power management      yes yes 254/0xFE
> automatic acoustic management  no no
> media status notification      no no
> power-up in Standby            yes no
> write-read-verify              no no
> unload                         yes yes
> free-fall                      no no
> Data Set Management (DSM/TRIM) yes
> DSM - max 512byte blocks       yes              1
> DSM - deterministic read       yes              any value
> Host Protected Area (HPA)      yes      no      234441648/234441648
> HPA - Security                 no
> 
> I don't see BIO_DELETE called out in the camcontrol output anywhere else 
> but and the DSM/TRIM line is marked as supported with the enabled column 
> ambiguous :-)

Yes thats what your looking for, attached to ataX this will
be using ATA_TRIM requests to support BIO_DELETE.

So the question is now have you simply not seen any data
removed from your L2ARC vdev's or is there an issue with
the L2ARC TRIM support.

One way to try and force test this would be get your L2ARC
full of data which you then remove from the pool as that
should then be removed from L2ARC and hence TRIM'ed.

"zfs-stats -L" or "sysctl -a |grep -i l2" should be helpful
on checking stats for this.

    Regards
    Steve

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