| From: | Shridhar Daithankar <shridhar_daithankar(at)persistent(dot)co(dot)in> |
|---|---|
| To: | Andrew Sullivan <andrew(at)libertyrms(dot)info> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Some thoughts about i/o priorities and throttling vacuum |
| Date: | 2003-10-17 13:55:13 |
| Message-ID: | 3F8FF4C1.7020906@persistent.co.in |
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| Lists: | pgsql-hackers |
Andrew Sullivan wrote:
> On Fri, Oct 17, 2003 at 07:04:45PM +0530, Shridhar Daithankar wrote:
>
>>I am slightly confused here. IIRC pg_autovacuum never did a vacuum full. At
>>the most it does vacuum /vacuum analyse, none of which chew disk bandwidth.
>
>
> The latter is false. VACUUM FULL certainly uses _more_ disk
> bandwidth than VACUUM, but it's just false that plain VACUUM doesn't
> contend for disk. And if you're already maxed, then that extra
> bandwidth you cannot afford.
What part of plain vacuum takes disk bandwidth? WAL? Clog? Certainly not data
files themselves, right?
OK, I understand some system can be saturated enough to have additional WAL/Clog
burdon, but genuinely curious, how much disk bandwidth is required for plain
vacuum and what are the factors it depends upon?
Shridhar
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