zfs discuss - Feb 2010 - l2arc current usage (population size)

Hello,

How do you tell how much of your l2arc is populated? I''ve been looking
for a while now, can''t seem to find it.

Must be easy, as this blog entry shows it over time:

http://blogs.sun.com/brendan/entry/l2arc_screenshots

And follow up, can you tell how much of each data set is in the arc or l2arc?
-- 
This message posted from opensolaris.org

On 19 February, 2010 - Christo Kutrovsky sent me these 0,5K bytes:
> Hello,
> 
> How do you tell how much of your l2arc is populated? I''ve been
looking for a while now, can''t seem to find it.
> 
> Must be easy, as this blog entry shows it over time:
> 
> http://blogs.sun.com/brendan/entry/l2arc_screenshots
> 
> And follow up, can you tell how much of each data set is in the arc or
l2arc?
kstat -m zfs
(p, c, l2arc_size)

arc_stat.pl is good, but doesn''t show l2arc..

/Tomas
-- 
Tomas ?gren, stric at acc.umu.se, http://www.acc.umu.se/~stric/
|- Student at Computing Science, University of Ume?
`- Sysadmin at {cs,acc}.umu.se

Am 20.02.10 03:22, schrieb Tomas ?gren:
> On 19 February, 2010 - Christo Kutrovsky sent me these 0,5K bytes:
>> How do you tell how much of your l2arc is populated? I''ve been
looking for a while now, can''t seem to find it.
>>
>> Must be easy, as this blog entry shows it over time:
>>
>> http://blogs.sun.com/brendan/entry/l2arc_screenshots
>>
>> And follow up, can you tell how much of each data set is in the arc or
l2arc?
>
> kstat -m zfs
> (p, c, l2arc_size)
>
> arc_stat.pl is good, but doesn''t show l2arc..
zpool iostat -v <poolname> would also do the trick for l2arc.
>
> /Tomas
- Felix

On 21 February, 2010 - Felix Buenemann sent me these 0,7K bytes:
> Am 20.02.10 03:22, schrieb Tomas ?gren:
>> On 19 February, 2010 - Christo Kutrovsky sent me these 0,5K bytes:
>>> How do you tell how much of your l2arc is populated? I''ve
been looking for a while now, can''t seem to find it.
>>>
>>> Must be easy, as this blog entry shows it over time:
>>>
>>> http://blogs.sun.com/brendan/entry/l2arc_screenshots
>>>
>>> And follow up, can you tell how much of each data set is in the arc
or l2arc?
>>
>> kstat -m zfs
>> (p, c, l2arc_size)
>>
>> arc_stat.pl is good, but doesn''t show l2arc..
>
> zpool iostat -v <poolname> would also do the trick for l2arc.
No, it will show how much of the disk has been visited (dirty blocks)
but not how much it occupies right now. At least very obvious difference
if you add a zvol as cache..

If it had supported TRIM or similar, they would probably be about the
same though.

/Tomas
-- 
Tomas ?gren, stric at acc.umu.se, http://www.acc.umu.se/~stric/
|- Student at Computing Science, University of Ume?
`- Sysadmin at {cs,acc}.umu.se

On Feb 21, 2010, at 9:18 AM, Tomas ?gren wrote:
> On 21 February, 2010 - Felix Buenemann sent me these 0,7K bytes:
> 
>> Am 20.02.10 03:22, schrieb Tomas ?gren:
>>> On 19 February, 2010 - Christo Kutrovsky sent me these 0,5K bytes:
>>>> How do you tell how much of your l2arc is populated?
I''ve been looking for a while now, can''t seem to find it.
>>>> 
>>>> Must be easy, as this blog entry shows it over time:
>>>> 
>>>> http://blogs.sun.com/brendan/entry/l2arc_screenshots
>>>> 
>>>> And follow up, can you tell how much of each data set is in the
arc or l2arc?
>>> 
>>> kstat -m zfs
>>> (p, c, l2arc_size)
>>> 
>>> arc_stat.pl is good, but doesn''t show l2arc..
>> 
>> zpool iostat -v <poolname> would also do the trick for l2arc.
> 
> No, it will show how much of the disk has been visited (dirty blocks)
> but not how much it occupies right now. At least very obvious difference
> if you add a zvol as cache..
> 
> If it had supported TRIM or similar, they would probably be about the
> same though.
Don''t confuse the ZIL with L2ARC.  TRIM will do little for L2ARC
devices.
 -- richard

ZFS storage and performance consulting at http://www.RichardElling.com
ZFS training on deduplication, NexentaStor, and NAS performance
http://nexenta-atlanta.eventbrite.com (March 15-17, 2010)

On 21 February, 2010 - Richard Elling sent me these 1,3K bytes:
> On Feb 21, 2010, at 9:18 AM, Tomas ?gren wrote:
> 
> > On 21 February, 2010 - Felix Buenemann sent me these 0,7K bytes:
> > 
> >> Am 20.02.10 03:22, schrieb Tomas ?gren:
> >>> On 19 February, 2010 - Christo Kutrovsky sent me these 0,5K
bytes:
> >>>> How do you tell how much of your l2arc is populated?
I''ve been looking for a while now, can''t seem to find it.
> >>>> 
> >>>> Must be easy, as this blog entry shows it over time:
> >>>> 
> >>>> http://blogs.sun.com/brendan/entry/l2arc_screenshots
> >>>> 
> >>>> And follow up, can you tell how much of each data set is
in the arc or l2arc?
> >>> 
> >>> kstat -m zfs
> >>> (p, c, l2arc_size)
> >>> 
> >>> arc_stat.pl is good, but doesn''t show l2arc..
> >> 
> >> zpool iostat -v <poolname> would also do the trick for
l2arc.
> > 
> > No, it will show how much of the disk has been visited (dirty blocks)
> > but not how much it occupies right now. At least very obvious
difference
> > if you add a zvol as cache..
> > 
> > If it had supported TRIM or similar, they would probably be about the
> > same though.
> 
> Don''t confuse the ZIL with L2ARC.  TRIM will do little for L2ARC
devices.
I was mostly thinking about the "telling the backing device that block X
isn''t in use anymore", not the performance part.. If I have an
L2ARC
backed by a zvol without compression, the "used" size will grow until
it''s full, even if L2ARC doesn''t use all of it currently.

/Tomas
-- 
Tomas ?gren, stric at acc.umu.se, http://www.acc.umu.se/~stric/
|- Student at Computing Science, University of Ume?
`- Sysadmin at {cs,acc}.umu.se

Thanks Tomas,

I got what I needed, and more. The header size is of particular interest.

On Fri, Feb 19, 2010 at 9:22 PM, Tomas ?gren <stric at acc.umu.se> wrote:
> On 19 February, 2010 - Christo Kutrovsky sent me these 0,5K bytes:
>
> > Hello,
> >
> > How do you tell how much of your l2arc is populated? I''ve
been looking
> for a while now, can''t seem to find it.
> >
> > Must be easy, as this blog entry shows it over time:
> >
> > http://blogs.sun.com/brendan/entry/l2arc_screenshots
> >
> > And follow up, can you tell how much of each data set is in the arc or
> l2arc?
>
> kstat -m zfs
> (p, c, l2arc_size)
>
> arc_stat.pl is good, but doesn''t show l2arc..
>
> /Tomas
> --
> Tomas ?gren, stric at acc.umu.se,
http://www.acc.umu.se/~stric/<http://www.acc.umu.se/%7Estric/>
> |- Student at Computing Science, University of Ume?
> `- Sysadmin at {cs,acc}.umu.se
>
--
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