Re: Amazon High I/O instances

You set shared_buffers way below what is suggested in Greg Smith book (25%
or more of RAM) .. what is the rationale behind that rule of thumb ? Other
values are more or less what I set, though I could lower the
effective_cache_size and vfs.zfs.arc_max and see how it goes.

Sébastien

On Wed, Sep 12, 2012 at 7:24 PM, John R Pierce <pierce(at)hogranch(dot)com> wrote:

> On 09/12/12 4:03 PM, Sébastien Lorion wrote:
>
>> I agree 1GB is a lot, I played around with that value, but it hardly
>> makes a difference. Is there a plateau in how that value affects query
>> performance ? On a master DB, I would set it low and raise as necessary,
>> but what would be a good average value on a read-only DB with same spec and
>> max_connections ?
>>
>
> a complex query can require several times work_mem for sorts and hash
> merges. how many queries do you expect to ever be executing
> concurrently? I'll take 25% of my system memory and divide it by
> 'max_connections' and use that as work_mem for most cases.
>
> on a large memory system doing dedicated transaction processing, I
> generally shoot for about 50% of the server memory as disk cache, 1-2GB as
> shared_buffers, 512MB-2GB as maintenance_work_mem, and 20-25% as work_mem
> (divided by max_connections)
>
>
>
>
> --
> john r pierce N 37, W 122
> santa cruz ca mid-left coast
>
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