Re: Amazon High I/O instances

[Sébastien Lorion <sl@xxxxxxxxxxxxxxxxxxxxx>]

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 <sl@xxxxxxxxxxxxxxxxxxxxx> 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 <pierce@xxxxxxxxxxxx> 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.

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




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