Re: pg_basebackup blocking all queries with horrible performance

On Thu, Jun 7, 2012 at 12:40 PM, Magnus Hagander <magnus@hagander.net> wrote:
> On Thu, Jun 7, 2012 at 8:04 PM, Lonni J Friedman <netllama@gmail.com> wrote:
>> On Thu, Jun 7, 2012 at 10:41 AM, Lonni J Friedman <netllama@gmail.com> wrote:
>>> Greetings,
>>> I have a 4 server postgresql-9.1.3 cluster (one master doing streaming
>>> replication to 3 hot standby servers).  All of them are running
>>> Fedora-16-x86_64.
>>>
>>> http://wiki.postgresql.org/wiki/Lock_Monitoring
>>
>> err, i included that URL but neglected to explain why.  On a different
>> list someone suggested that I verify that there were no locks that
>> were blocking things, and I did so, and found no locks.
>>
>> So I'm still at a loss why pg_basebackup is killing perf, and would
>> appreciate pointers on how to debug it or at least reduce its impact
>> on performance if that is possible.
>>
>
> My guess would be that you are overloading your I/O system. You should
> look at values from iostat and vmstat from when the system works fine
> and when you run pg_basebackup, that should give you a hint in the
> right direction.

ok, thanks.  i'll take a look at that.  If this turns out to be the
issue, is there some way to get pg_basebackup to run more slowly, so
that it has less impact?  Or could I do this with ionice on the
pg_basebackup process?