recommended memory for zfs

[Benjamin Adams]

On 05/09/2013 08:53 PM, Shane Ambler wrote:
> On 09/05/2013 22:48, Benjamin Adams wrote:
>> Hello zfs question about memory.
>> I heard zfs is very ram hungry.
>> Service looking to run:
>> - nginx
>> - postgres
>> - php-fpm
>> - python
>>
>> I have a machine with two quad core cpus but only 4 G Memory
>>
>> I'm looking to buy more ram now.
>> What would be the recommend amount of memory for zfs across 6 drives on
>> this setup?
>>
>
> I believe I heard a calculation of 1GB cache per 1TB of disk. But 
> basically zfs will use all free ram available if you access that much 
> data from disk. You will want to set vfs.zfs.arc_max to allow enough 
> ram for your apps to work in.
>
> If you consider the files for your website and the data you store you 
> may find that you would never fill more than 500MB of cache.
>
> If you will be serving large media files that will easily use up the 
> cache you could give them their own filesystem that only caches 
> metadata - zfs set primarycache=metadata zroot/mediafiles
>
>
Thanks for all the replies  Size of DB and HD's are:

Current DB Size = 23 GB
HD sizes = (6) 500 GB drives