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Creating One Database Device

6 posts in Windows NT Last posting was on 2000-04-17 20:03:18.0Z
Joe Gregory Posted on 2000-04-03 18:43:21.0Z
Message-ID: <38E8E648.8CC1D6BD@npt.nuwc.navy.mil>
Date: Mon, 03 Apr 2000 14:43:21 -0400
From: Joe Gregory <gregoryj@npt.nuwc.navy.mil>
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I am in the process of planning my upgrade from 11.9.2 runing hpux 10.02
on an HP box to NT platform running SAE 12.0. Does anyone know why I
should not, (or should), define one large database device to create all
my databases on. Instead of defining database devices for each
database. The NT box I will be upgrading to will have RAID 5 drives with
128 meg of cache.


Eric T. J. Hogue Posted on 2000-04-10 13:26:24.0Z
From: "Eric T. J. Hogue" <Eric.Hogue@wpafb.af.mil>
References: <38E8E648.8CC1D6BD@npt.nuwc.navy.mil>
Subject: Re: Creating One Database Device
Date: Mon, 10 Apr 2000 09:26:24 -0400
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Corruption. If you have one device with everything, and it becomes corrupt
through a software glitch, you will harm recoverability because you won't
have
an accessible log. If your log and database are on separate devices, you be
able to use back-ups plus the log file to fully recover if the data file
becomes
corrupted.

Using a similar setup, I found it was easiest to put exactly one database
file
on one device, and it's log file on one device. That's gives me three files
for each database (the third being the dump file).

Eric

"Joe Gregory" <gregoryj@npt.nuwc.navy.mil> wrote in message
news:38E8E648.8CC1D6BD@npt.nuwc.navy.mil...
> I am in the process of planning my upgrade from 11.9.2 runing hpux 10.02
> on an HP box to NT platform running SAE 12.0. Does anyone know why I
> should not, (or should), define one large database device to create all
> my databases on. Instead of defining database devices for each
> database. The NT box I will be upgrading to will have RAID 5 drives with
> 128 meg of cache.
>


Bill Robinette Posted on 2000-04-03 20:06:11.0Z
From: "Bill Robinette" <William.Robinette@ValueOptions.com>
References: <38E8E648.8CC1D6BD@npt.nuwc.navy.mil>
Subject: Re: Creating One Database Device
Date: Mon, 3 Apr 2000 16:06:11 -0400
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Do not do that! You will get very very very poor performance. Create logs
and data on separate devices.

Joe Gregory <gregoryj@npt.nuwc.navy.mil> wrote in message
news:38E8E648.8CC1D6BD@npt.nuwc.navy.mil...
> I am in the process of planning my upgrade from 11.9.2 runing hpux 10.02
> on an HP box to NT platform running SAE 12.0. Does anyone know why I
> should not, (or should), define one large database device to create all
> my databases on. Instead of defining database devices for each
> database. The NT box I will be upgrading to will have RAID 5 drives with
> 128 meg of cache.
>


Alberto da Silva Posted on 2000-04-10 18:39:29.0Z
Reply-To: "Alberto da Silva" <Alberto.daSilva@rmb.co.za>
From: "Alberto da Silva" <Alberto.daSilva@rmb.co.za>
References: <38E8E648.8CC1D6BD@npt.nuwc.navy.mil> <L7ZaGwan$GA.299@forums.sybase.com>
Subject: Re: Creating One Database Device
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"Bill Robinette" <William.Robinette@ValueOptions.com> wrote in message
news:L7ZaGwan$GA.299@forums.sybase.com...
> Do not do that! You will get very very very poor performance. Create logs
> and data on separate devices.

No! - you will acually get better performance!

Since the underlying device consists of a number of disks,
you are in effect load balancing the disks (and improving reliability
RAID5).

You MUST:
1) make sure that your RAID5 controller has a battery (eg. Compaq Smart
Array A3200 has)
2) Configure the write cache on the controller to write back
This will cause the RAID5 controller to acknowledge write before they
are complete.
Since you have a battery backed cache this is fine.
3) Configure the RAID5 controller write cache to 80-90% of the available
RAID5 cache.

Since RAID5 write are slower options (2) and (3) will make up for that.
Your reads will be faster - more disks.
You need to write bursts of over 100MB (80%) before the controller becomes a
problem.
Often if you are writing this much, then data being written fits the RAID5
stripe and the overhead drops
to that of a RAID1 device.

The RAID5 controller read cache is of little use if your server has a decent
amount of RAM
and Sybase is configured to use it "sp_configure 'total
memory',TOTALRAM-NTOverhead"
If you server has say 512MB RAM, the RAID5 controller read cache will
virtually always
be defeated.

I'm not sure if it's better to have 1 "disk init" or lots of "disk init"s.

Hope this helps,

Alberto
mailto:ads@rmb.co.za


> Joe Gregory <gregoryj@npt.nuwc.navy.mil> wrote in message
> news:38E8E648.8CC1D6BD@npt.nuwc.navy.mil...
> > I am in the process of planning my upgrade from 11.9.2 runing hpux 10.02
> > on an HP box to NT platform running SAE 12.0. Does anyone know why I
> > should not, (or should), define one large database device to create all
> > my databases on. Instead of defining database devices for each
> > database. The NT box I will be upgrading to will have RAID 5 drives with
> > 128 meg of cache.


Bill Robinette Posted on 2000-04-17 20:03:18.0Z
From: "Bill Robinette" <William.Robinette@ValueOptions.com>
References: <38E8E648.8CC1D6BD@npt.nuwc.navy.mil> <L7ZaGwan$GA.299@forums.sybase.com> <EGWpizxo$GA.299@forums.sybase.com>
Subject: Re: Creating One Database Device
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I'll have to disagree about about the performance issue. According to Sybase
and several independant consultants and my own performance testing on NT and
UNIX , RAID 5 is not fater than a separate disk configuration.

I'll agree that reads will be faster if that is all you are doing. Add
several users trying to read and a few trying to write (logged) you are in
for a boittleneck.

Alberto da Silva <Alberto.daSilva@rmb.co.za> wrote in message
news:EGWpizxo$GA.299@forums.sybase.com...
>
> "Bill Robinette" <William.Robinette@ValueOptions.com> wrote in message
> news:L7ZaGwan$GA.299@forums.sybase.com...
> > Do not do that! You will get very very very poor performance. Create
logs
> > and data on separate devices.
>
> No! - you will acually get better performance!
>
> Since the underlying device consists of a number of disks,
> you are in effect load balancing the disks (and improving reliability
> RAID5).
>
> You MUST:
> 1) make sure that your RAID5 controller has a battery (eg. Compaq Smart
> Array A3200 has)
> 2) Configure the write cache on the controller to write back
> This will cause the RAID5 controller to acknowledge write before they
> are complete.
> Since you have a battery backed cache this is fine.
> 3) Configure the RAID5 controller write cache to 80-90% of the available
> RAID5 cache.
>
> Since RAID5 write are slower options (2) and (3) will make up for that.
> Your reads will be faster - more disks.
> You need to write bursts of over 100MB (80%) before the controller becomes
a
> problem.
> Often if you are writing this much, then data being written fits the RAID5
> stripe and the overhead drops
> to that of a RAID1 device.
>
> The RAID5 controller read cache is of little use if your server has a
decent
> amount of RAM
> and Sybase is configured to use it "sp_configure 'total
> memory',TOTALRAM-NTOverhead"
> If you server has say 512MB RAM, the RAID5 controller read cache will
> virtually always
> be defeated.
>
> I'm not sure if it's better to have 1 "disk init" or lots of "disk init"s.
>
> Hope this helps,
>
> Alberto
> mailto:ads@rmb.co.za
>
>
> > Joe Gregory <gregoryj@npt.nuwc.navy.mil> wrote in message
> > news:38E8E648.8CC1D6BD@npt.nuwc.navy.mil...
> > > I am in the process of planning my upgrade from 11.9.2 runing hpux
10.02
> > > on an HP box to NT platform running SAE 12.0. Does anyone know why I
> > > should not, (or should), define one large database device to create
all
> > > my databases on. Instead of defining database devices for each
> > > database. The NT box I will be upgrading to will have RAID 5 drives
with
> > > 128 meg of cache.
>
>
>


Joe Gregory Posted on 2000-04-04 13:24:50.0Z
Message-ID: <38E9ED22.58B27D56@npt.nuwc.navy.mil>
Date: Tue, 04 Apr 2000 09:24:50 -0400
From: Joe Gregory <gregoryj@npt.nuwc.navy.mil>
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If I put this database device on my raid 5 device I am striping the device
accross
7 disks. This device also has 128 meg of cache. This is why I not sure of what
performance I will get from it.

Bill Robinette wrote:

> Do not do that! You will get very very very poor performance. Create logs
> and data on separate devices.
>
> Joe Gregory <gregoryj@npt.nuwc.navy.mil> wrote in message
> news:38E8E648.8CC1D6BD@npt.nuwc.navy.mil...
> > I am in the process of planning my upgrade from 11.9.2 runing hpux 10.02
> > on an HP box to NT platform running SAE 12.0. Does anyone know why I
> > should not, (or should), define one large database device to create all
> > my databases on. Instead of defining database devices for each
> > database. The NT box I will be upgrading to will have RAID 5 drives with
> > 128 meg of cache.
> >