raid on emc

[utkanbir]

Hi Gurus and Mr.Kagel,

This subject discussed many times before : raid 5 versus raid 10 or 01
..
The story is same , the question is same but i am little bit confused
..
This is Oracle related , but i am new with oracle , but experienced
with informix , thats why i send it here.

I am setting up a large datawarehouse on Oracle RAC with Emc disk
array.
The emc site suggest to use raid 5 , i want to use raid 10 or 01
because of the points that were discussed on this forum .

Since the system is datawarehouse and dss type , i will have no write
.. So if i use raid 5 , i will have no write performance problem.
(Right?)

What is the performance benefit of raid 10 against raid 5 ?

And , the disk crashes problem : If one disk fails , raid 5 is ok , if
two fail , it is hell. If we think the emc box , do i have to consider
such a problem ?


Kind Regards,
hope

[Art S. Kagel]

On Mon, 08 Sep 2003 06:12:11 -0400, utkanbir wrote:

NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5

> Hi Gurus and Mr.Kagel,
>
> This subject discussed many times before : raid 5 versus raid 10 or 01 . The
> story is same , the question is same but i am little bit confused . This is
> Oracle related , but i am new with oracle , but experienced with informix ,
> thats why i send it here.
>
> I am setting up a large datawarehouse on Oracle RAC with Emc disk array. The
> emc site suggest to use raid 5 , i want to use raid 10 or 01 because of the
> points that were discussed on this forum .
>
> Since the system is datawarehouse and dss type , i will have no write
> . So if i use raid 5 , i will have no write performance problem. (Right?)

No online writes but what about your dataloads? Can you afford for a dataload
to take 50% longer than it could?

> What is the performance benefit of raid 10 against raid 5 ?

Mostly write performance. There is a slight readtime benefit to any mirrored
system (RAID1/01/10/6/7) over RAID2/3/4/5 caused by being able to read sectors
from both sides of the mirror concurrently, but this is rarely important.

The biggest performance difference is at drive recovery time. A 5 drive RAID5
array will suffer a performance degradation during rebuilding of as much as 80%
while a 4 pair RAID10 array will only experience a 20% performance hit (or less
if the rebuilding pair is not actively being read).

> And , the disk crashes problem : If one disk fails , raid 5 is ok , if two
> fail , it is hell. If we think the emc box , do i have to consider such a
> problem ?

Only if you like you data and your job.

Art S. Kagel

> Kind Regards,
> hope

[utkanbir]

Mr.Kagel,

Thank you very much for your help.

Kind Regards,
hope


"Art S. Kagel" <kagel@bloomberg.net> wrote in message news:<pan.2003.09.08.13.16.41.581655.10594@bloombe rg.net>...

> On Mon, 08 Sep 2003 06:12:11 -0400, utkanbir wrote:
>
> NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5
>

> > Hi Gurus and Mr.Kagel,
> >
> > This subject discussed many times before : raid 5 versus raid 10 or 01 . The
> > story is same , the question is same but i am little bit confused . This is
> > Oracle related , but i am new with oracle , but experienced with informix ,
> > thats why i send it here.
> >
> > I am setting up a large datawarehouse on Oracle RAC with Emc disk array. The
> > emc site suggest to use raid 5 , i want to use raid 10 or 01 because of the
> > points that were discussed on this forum .
> >
> > Since the system is datawarehouse and dss type , i will have no write
> > . So if i use raid 5 , i will have no write performance problem. (Right?)

>
> No online writes but what about your dataloads? Can you afford for a dataload
> to take 50% longer than it could?
>

> > What is the performance benefit of raid 10 against raid 5 ?

>
> Mostly write performance. There is a slight readtime benefit to any mirrored
> system (RAID1/01/10/6/7) over RAID2/3/4/5 caused by being able to read sectors
> from both sides of the mirror concurrently, but this is rarely important.
>
> The biggest performance difference is at drive recovery time. A 5 drive RAID5
> array will suffer a performance degradation during rebuilding of as much as 80%
> while a 4 pair RAID10 array will only experience a 20% performance hit (or less
> if the rebuilding pair is not actively being read).
>

> > And , the disk crashes problem : If one disk fails , raid 5 is ok , if two
> > fail , it is hell. If we think the emc box , do i have to consider such a
> > problem ?

>
> Only if you like you data and your job.
>
> Art S. Kagel
>

> > Kind Regards,
> > hope