Actually, while the shorthand method of */15 works, the
OLDER system is better...
After all, who wants to see spikes every 15 minutes as all
of the various cron jobs hit at 0, 15, 30 and 45 past? That's
why I always try to stagger them across a network:
3,18,33,48
2,17,32,47
1,16,31,46
*/15
etc.
However, even better than that is to allow a bit of fudge in
when the cron goes off... +/- a couple minutes, like this:
3,19,31,44
2,15,33,46
1,14,32,47
*/15
etc. While this doesn't give perfect spacing, it DOES allow
some bit of "load balancing" to occur, in the event that a
particular cron job takes a great deal of resources. Over time,
you would be able to track any places where further fine tuning
would help... These kinds of techniques went a long way to getting
some of the programs working well back "in the day", when every
night at midnight, all of the Cron jobs in creation went off
simultaneously... many a server came down to it's knees, because
it would start thrashing, etc., because 30-40 cron jobs, that only
took 10 minutes or so by themselves, would be contending for the same
groups of resources, particularly scarce RAM and Disk I/O time.
Bill Ward
-----Original Message-----
From: John Horne [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, May 01, 2001 8:11 AM
To: [EMAIL PROTECTED]
Subject: Re: run cron job every 15 minutes
On 30-Apr-01 at 15:51:51 rpjday wrote:
> On Mon, 30 Apr 2001, Paul Anderson wrote:
>> replace the 15 with 15 30 45 00. This will make the job run every 15
>> minutes.
>
> the above syntax won't work -- you need to separate multiple values
> for the same field with commas, not spaces. and there can't be any
> intervening spaces around the commas either.
>
> in either case, you're better off using the */15 syntax i mentioned
> earlier.
>
Why is that 'better'? I still use the old (?) syntax of '0,15,30,45' which
seems to work just as well.
John.
------------------------------------------------------------------------
John Horne, University of Plymouth, UK Tel: +44 (0)1752 233914
E-mail: [EMAIL PROTECTED]
PGP key available from public key servers
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