Re: VACUUM and 24/7 database operation

At 1/23/01 4:20 PM, Alfred Perlstein wrote:

>* Steve Wolfe <steve(at)iboats(dot)com> [010123 13:11] wrote:
>> Well, here's what it comes down to: Do you want updates to happen
>> quickly, and vacuum when load is low, or do you want updates to be slow all
>> the time? I suppose that there are some sites that can't find two minutes
>> per day when updates will block (not selects), but I imagine they're very
>> few.
>
>There are some sites where going for more than an hour without a
>VACUUM makes response times unnaceptable, and each vacuum can take
>20 minutes a run.

In addition, the suggestion that vacuum isn't a problem because it only
takes two minutes is misleading.

Sure, it's only 2 minutes out of 24 hours. However, any given visitor
isn't at my site for 24 hours. If she arrives just as I'm starting the
vacuum, and it takes her less than two minutes to give up and go
somewhere else, the site was unavailable 100% of the time as far as she's
concerned.

If your site is down two minutes a day, and you have 14,000 unique
visitors a week, each of whom requires a database update, that's 20
people a week for whom the site isn't working when they arrive.

--
Robert L Mathews, Tiger Technologies