Joshua D. Drake wrote:
> Hans-Juergen Schoenig wrote:
>
>>> regards, tom lane
>>>
>>
>>
>> overhead is not an issue here - if i lose 10 or 15% i am totally fine
>> as long as i can reduce vacuum overhead to an absolute minimum.
>> overhead will vary with row sizes anyway - this is not the point.
>
> I am not buying this argument. If you have a 5TB database, I am going
> to assume you put it on enterprise class hardware. Enterprise class
> hardware can handle the I/O required to appropriately run vacuum.
>
> We have a customer that is constantly running 5 autovacuum workers on
> only 28 spindles. We are in the process of upgrading them to 50
> spindles at which point I will likely try 10 autovacuum workers.
>
i forgot to mention - i am on 8.1 here.
so, VACUUM is not so smart yet.
my changes are pretty much random I/O - so tuple header does not
contribute to a lot more I/O as i have to read entire blocks anway.
this is why i said - it is not that kind of an issue.
and no, updating is not a 5 min task ...
hans
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