Re: Amazon High I/O instances

On 09/12/12 4:49 PM, Sébastien Lorion wrote:
> 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.

I think those 25% rules were typically created when ram was no more than
4-8GB.

for our highly transactional workload, at least, too large of a
shared_buffers seems to slow us down, perhaps due to higher overhead of
managing that many 8k buffers.    I've heard other read-mostly
workloads, such as data warehousing, can take advantage of larger buffer
counts.



--
john r pierce                            N 37, W 122
santa cruz ca                         mid-left coast