One more question .. I could not set wal_sync_method to anything else but fsync .. is that expected or should other choices be also available ? I am not sure how the EC2 SSD cache flushing is handled on EC2, but I hope it is flushing the whole cache on every sync .. As a side note, I got corrupted databases (errors about pg_xlog directories not found, etc) at first when running my tests, and I suspect it was because of vfs.zfs.cache_flush_disable=1, though I cannot prove it for sure.
Sébastien On Wed, Sep 12, 2012 at 8:49 PM, Sébastien Lorion <s...@thestrangefactory.com>wrote: > Is dedicating 2 drives for WAL too much ? Since my whole raid is comprised > of SSD drives, should I just put it in the main pool ? > > Sébastien > > > On Wed, Sep 12, 2012 at 8:28 PM, Sébastien Lorion < > s...@thestrangefactory.com> wrote: > >> Ok, make sense .. I will update that as well and report back. Thank you >> for your advice. >> >> Sébastien >> >> >> On Wed, Sep 12, 2012 at 8:04 PM, John R Pierce <pie...@hogranch.com>wrote: >> >>> 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 >>> >>> >>> >>> >>> -- >>> Sent via pgsql-general mailing list (pgsql-general@postgresql.org) >>> To make changes to your subscription: >>> http://www.postgresql.org/**mailpref/pgsql-general<http://www.postgresql.org/mailpref/pgsql-general> >>> >> >> >
