[zfs-discuss] PostgreSQL on ZFS

Sander Klein roedie at roedie.nl
Sat Oct 19 14:39:35 EDT 2013

On 19.10.2013 19:52, Gregor Kopka wrote:
> Am 19.10.2013 18:56, schrieb Durval Menezes:
>> I'm very interested in this. What is a "good/safe" arc/l2arc 
>> proportion?
>> On Oct 19, 2013 1:52 PM, "Fajar A. Nugraha" <list at fajar.net> wrote:
>>> On Sat, Oct 19, 2013 at 8:45 PM, Gregor Kopka <gregor at kopka.net> 
>>> wrote:
>>>> Am 19.10.2013 12:11, schrieb Sander Klein:
>>>>> The ARC is limited at 32G and it has a big L2ARC of 200G.
>>>> ARC needs to hold the headers for the L2ARC, with a small ARC and 
>>>> enough L2ARC zfs can paint itself in a corner.
>>> Surely 32G ARC is more than enough to hold headers for 200G L2ARC?
>  A quick search brought me this
> http://www.mail-archive.com/zfs-discuss@opensolaris.org/msg34677.html
> [1]

Thanks very much Gregor. It never crossed my mind that the ARC must 
hold the headers for the L2ARC. Moreover, since I use an 8K recordsize 
the ARC must hold much more headers than if I used the 128K recordsize. 
This is why I never hit the limit before on any of my other servers.

I will make the ARC bigger.



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