I think it really bores down to the physical disk spindles - if you can
split your physical and logical logs off onto different disks, you will
have better performance.
These logs are used intensely, and you don't want other data to share
the same disks. Well, you can share disks, but for best performance you
should split and keep these logs separate.



-----Original Message-----
From: owner-informix-list@iiug.org [mailtowner-informix-list@iiug.org]
On Behalf Of Andy Kent
Sent: Tuesday, April 06, 2004 2:19 PM
To: informix-list@iiug.org
Subject: Why put logs away from rootdbs?

What are the reasons why Informix keeps on about moving your logical
and physical logs away from rootdbs? Surely if the whole instance is
going into a single RAID 1+0 array it doesn't make any difference? OK,
a bit more to glean from onstat -D perhaps, but is there any other
benefit?

In a rare break with tradition for me, this is a REAL, IN-USE email
address.

Andy Kent

sending to informix-list

"Dirk Moolman" <DirkM@mxgroup.co.za> wrote in message
news:c4umft$d2$1@terabinaries.xmission.com...
>
> I think it really bores down to the physical disk spindles - if you can
> split your physical and logical logs off onto different disks, you will
> have better performance.

and put alternate logical logs on seperate disks. Whilst ontape/onbar is
backup up on you can be writing to the next one without disk contention.

Also the physical log (and also each logical log) is always a sequential
write
so put it on a seperate disk so that the disk heads don't move away from
where they need to be.


> These logs are used intensely, and you don't want other data to share
> the same disks. Well, you can share disks, but for best performance you
> should split and keep these logs separate.
>
>
>
> -----Original Message-----
> From: owner-informix-list@iiug.org [mailtowner-informix-list@iiug.org]
> On Behalf Of Andy Kent
> Sent: Tuesday, April 06, 2004 2:19 PM
> To: informix-list@iiug.org
> Subject: Why put logs away from rootdbs?
>
> What are the reasons why Informix keeps on about moving your logical
> and physical logs away from rootdbs? Surely if the whole instance is
> going into a single RAID 1+0 array it doesn't make any difference? OK,
> a bit more to glean from onstat -D perhaps, but is there any other
> benefit?
>
> In a rare break with tradition for me, this is a REAL, IN-USE email
> address.
>
> Andy Kent
>
> sending to informix-list

Sure, that's the conventional wisdom, but surely RAID blows all that
away? I can think of some reasons why you'd still have separate
dbspaces (static vs volatile tables, temp dbspaces, critical vs.
non-critical ... ), but what I'm at a loss to understand is why one
would need to separate rootdbs and logs on an all-RAID box.

Andy

"David Williams" <djw@smooth1.fsnet.co.uk> wrote in message news:<c4uv0q$mo0$1@news6.svr.pol.co.uk>...
> "Dirk Moolman" <DirkM@mxgroup.co.za> wrote in message
> news:c4umft$d2$1@terabinaries.xmission.com...
> >
> > I think it really bores down to the physical disk spindles - if you can
> > split your physical and logical logs off onto different disks, you will
> > have better performance.
>
> and put alternate logical logs on seperate disks. Whilst ontape/onbar is
> backup up on you can be writing to the next one without disk contention.
>
> Also the physical log (and also each logical log) is always a sequential
> write
> so put it on a seperate disk so that the disk heads don't move away from
> where they need to be.
>
>
> > These logs are used intensely, and you don't want other data to share
> > the same disks. Well, you can share disks, but for best performance you
> > should split and keep these logs separate.
> >
> >
> >
> > -----Original Message-----
> > From: owner-informix-list@iiug.org [mailtowner-informix-list@iiug.org]
> > On Behalf Of Andy Kent
> > Sent: Tuesday, April 06, 2004 2:19 PM
> > To: informix-list@iiug.org
> > Subject: Why put logs away from rootdbs?
> >
> > What are the reasons why Informix keeps on about moving your logical
> > and physical logs away from rootdbs? Surely if the whole instance is
> > going into a single RAID 1+0 array it doesn't make any difference? OK,
> > a bit more to glean from onstat -D perhaps, but is there any other
> > benefit?
> >
> > In a rare break with tradition for me, this is a REAL, IN-USE email
> > address.
> >
> > Andy Kent
> >
> > sending to informix-list

"Andy Kent" <andykent.bristol1095@virgin.net> wrote in message
news:ac5fb36.0404070335.68fb3685@posting.google.co m...
> Sure, that's the conventional wisdom, but surely RAID blows all that
> away? I can think of some reasons why you'd still have separate
> dbspaces (static vs volatile tables, temp dbspaces, critical vs.
> non-critical ... ), but what I'm at a loss to understand is why one
> would need to separate rootdbs and logs on an all-RAID box.
>

Logs are continually written to and the logs are sequential writes.
You do not want the disk heads continually moving from data
to logs to data to logs to data to logs...

You can stripe the logs but not on the same disks as the data.

> Andy
>
> "David Williams" <djw@smooth1.fsnet.co.uk> wrote in message
news:<c4uv0q$mo0$1@news6.svr.pol.co.uk>...
> > "Dirk Moolman" <DirkM@mxgroup.co.za> wrote in message
> > news:c4umft$d2$1@terabinaries.xmission.com...
> > >
> > > I think it really bores down to the physical disk spindles - if you
can
> > > split your physical and logical logs off onto different disks, you
will
> > > have better performance.
> >
> > and put alternate logical logs on seperate disks. Whilst ontape/onbar
is
> > backup up on you can be writing to the next one without disk
contention.
> >
> > Also the physical log (and also each logical log) is always a
sequential
> > write
> > so put it on a seperate disk so that the disk heads don't move away
from
> > where they need to be.
> >
> >
> > > These logs are used intensely, and you don't want other data to share
> > > the same disks. Well, you can share disks, but for best performance
you
> > > should split and keep these logs separate.
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: owner-informix-list@iiug.org
[mailtowner-informix-list@iiug.org]
> > > On Behalf Of Andy Kent
> > > Sent: Tuesday, April 06, 2004 2:19 PM
> > > To: informix-list@iiug.org
> > > Subject: Why put logs away from rootdbs?
> > >
> > > What are the reasons why Informix keeps on about moving your logical
> > > and physical logs away from rootdbs? Surely if the whole instance is
> > > going into a single RAID 1+0 array it doesn't make any difference? OK,
> > > a bit more to glean from onstat -D perhaps, but is there any other
> > > benefit?
> > >
> > > In a rare break with tradition for me, this is a REAL, IN-USE email
> > > address.
> > >
> > > Andy Kent
> > >
> > > sending to informix-list

"David Williams" <djw@smooth1.fsnet.co.uk> wrote in message
news:c51p7r$107$1@news6.svr.pol.co.uk...
>
> "Andy Kent" <andykent.bristol1095@virgin.net> wrote in message
> news:ac5fb36.0404070335.68fb3685@posting.google.co m...
> > Sure, that's the conventional wisdom, but surely RAID blows all that
> > away? I can think of some reasons why you'd still have separate
> > dbspaces (static vs volatile tables, temp dbspaces, critical vs.
> > non-critical ... ), but what I'm at a loss to understand is why one
> > would need to separate rootdbs and logs on an all-RAID box.
> >
>
> Logs are continually written to and the logs are sequential writes.
> You do not want the disk heads continually moving from data
> to logs to data to logs to data to logs...
>
> You can stripe the logs but not on the same disks as the data.

I think you're missing the point.

Quite. The point is, "does it make any difference on RAID?" Of course
it's what you'd do on JABOD.

Andy

> > You can stripe the logs but not on the same disks as the data.
>
> I think you're missing the point.