Just about to set up our new Oracle server. The box is a Dell PowerEdge
2850, Dual Xeon 3.6GHz with 4 Gb RAM and 4x 18Gb 15,000 RPM Drives. I am
about to set up the RAID array and am unsure as what would be best. I was
originally going to use RAID 5 but am unsure now as I have read so many bad
things about using it with Oracle. Some form of redundancy is requred so
here are my proposed alternatives:

1) 2x RAID 1 arrays - this would give me a total of 36Gb and as each volume
would be mirrored I would have the necessary fault tolerance. I could then
split data across the two arrays, i.e. Windows Server 2003 and system files
on one and data files on the other

2) 1x RAID 10 array - this would have the data striped over two disks which
would be mirrored to provide the fault tolerance. I would only have one
volume but there would be a performance increase due to the striping. I'm
not sure if there is much worth to having a stripe set with only two disks.

Any strong feelings or opinions?

Thanks.

--
Ric.

For the last few years, Oracle has recommended using a single RAID 10
array. They call it the SAME methodology (Stripe And Mirror
Everything). The thinking is that with today's caching controllers and
fast disks, you'll get a better I/O balance with a single RAID 10 array
than you would spending a lot of time trying to analyze I/O and moving
datafiles around. There's a white paper about it on OTN or Metalink.
We've been using this method on Dell servers and it works well.

Tom

<tdwilsonng@yahoo.com> wrote in message
news:1103648364.064077.18290@c13g2000cwb.googlegro ups.com...
> For the last few years, Oracle has recommended using a single RAID 10
> array. They call it the SAME methodology (Stripe And Mirror
> Everything). The thinking is that with today's caching controllers and
> fast disks, you'll get a better I/O balance with a single RAID 10 array
> than you would spending a lot of time trying to analyze I/O and moving
> datafiles around. There's a white paper about it on OTN or Metalink.
> We've been using this method on Dell servers and it works well.

That is quite reassuring as it was my thinking too. My main concern was
that only having four drives would make a RAID 10 array pointless as the
striping would only be over two disks. Do you think it is still worth it?

Yes, I think you're still better off with a single RAID 10 array, even
with just two disks.

Ric wrote:
> Just about to set up our new Oracle server. The box is a Dell PowerEdge
> 2850, Dual Xeon 3.6GHz with 4 Gb RAM and 4x 18Gb 15,000 RPM Drives. I am
> about to set up the RAID array and am unsure as what would be best. I was
> originally going to use RAID 5 but am unsure now as I have read so many bad
> things about using it with Oracle. Some form of redundancy is requred so
> here are my proposed alternatives:
>
> 1) 2x RAID 1 arrays - this would give me a total of 36Gb and as each volume
> would be mirrored I would have the necessary fault tolerance. I could then
> split data across the two arrays, i.e. Windows Server 2003 and system files
> on one and data files on the other
>
> 2) 1x RAID 10 array - this would have the data striped over two disks which
> would be mirrored to provide the fault tolerance. I would only have one
> volume but there would be a performance increase due to the striping. I'm
> not sure if there is much worth to having a stripe set with only two disks.
>
> Any strong feelings or opinions?
>
> Thanks.
>


With just 4 drives, I would go RAID5. Probably.

The horror stories you've read about RAID5 need to be read in context.
And then you need to realise the context you are in -namely, fairly
low-end hardware and not many hard disks. The horror stories probably do
not apply to the situation you find yourself in.

The decision might also depend, however, on what you intend doing with
this database. Is it warehouse, or OLTP? 10 users or 1000? Clearly, your
data volumes are not going to be very high, but the rest is just guesswork.

If you care to describe some of the "bad things" you've read about
RAID5, then I'm sure a reasoned discussion of them here could either
confirm some doubts or dispell others.

But dismissing all RAID 5 'on principle' is as bad as routinely
rebuilding all your indexes, or thinking that I/O bottlenecks have been
eliminated because you've stored tables and indexes in separate
tablespaces: it's a sweeping generalisation that can cause grief.

Regards
HJR

Ric wrote:

> Just about to set up our new Oracle server. The box is a Dell PowerEdge
> 2850, Dual Xeon 3.6GHz with 4 Gb RAM and 4x 18Gb 15,000 RPM Drives. I am
> about to set up the RAID array and am unsure as what would be best. I was
> originally going to use RAID 5 but am unsure now as I have read so many bad
> things about using it with Oracle. Some form of redundancy is requred so
> here are my proposed alternatives:
>
> 1) 2x RAID 1 arrays - this would give me a total of 36Gb and as each volume
> would be mirrored I would have the necessary fault tolerance. I could then
> split data across the two arrays, i.e. Windows Server 2003 and system files
> on one and data files on the other
>
> 2) 1x RAID 10 array - this would have the data striped over two disks which
> would be mirrored to provide the fault tolerance. I would only have one
> volume but there would be a performance increase due to the striping. I'm
> not sure if there is much worth to having a stripe set with only two disks.
>
> Any strong feelings or opinions?
>
> Thanks.

I second your concerns. I see no value in RAID 5 and would make the
decision of (1) or (2) based on a realistic appraisal of when you will
be able to purchase additional disks which, quite frankly, would be my
choice. After purchasing Oracle and the hardware ... why not get some
additional disks given the low cost.

Presumably you will want some room for archived log files, etc.
--
Daniel A. Morgan
University of Washington
damorgan@x.washington.edu
(replace 'x' with 'u' to respond)


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DA Morgan wrote:
> Ric wrote:
>
>> Just about to set up our new Oracle server. The box is a Dell
>> PowerEdge 2850, Dual Xeon 3.6GHz with 4 Gb RAM and 4x 18Gb 15,000 RPM
>> Drives. I am about to set up the RAID array and am unsure as what
>> would be best. I was originally going to use RAID 5 but am unsure now
>> as I have read so many bad things about using it with Oracle. Some
>> form of redundancy is requred so here are my proposed alternatives:
>>
>> 1) 2x RAID 1 arrays - this would give me a total of 36Gb and as each
>> volume would be mirrored I would have the necessary fault tolerance.
>> I could then split data across the two arrays, i.e. Windows Server
>> 2003 and system files on one and data files on the other
>>
>> 2) 1x RAID 10 array - this would have the data striped over two disks
>> which would be mirrored to provide the fault tolerance. I would only
>> have one volume but there would be a performance increase due to the
>> striping. I'm not sure if there is much worth to having a stripe set
>> with only two disks.
>>
>> Any strong feelings or opinions?
>>
>> Thanks.
>
>
> I second your concerns. I see no value in RAID 5

Hold that thought...

> and would make the
> decision of (1) or (2) based on a realistic appraisal of when you will
> be able to purchase additional disks which, quite frankly, would be my
> choice.

....and this one.

Now put the two together. Assume, just for the moment, that you have no
more money; that all hard disk manufacturers have gone out of business;
that the world's entire stock of hard disks on retailer's shelves has
disappeared. He's got four disks, in other words, and four disks is all
he's going to have.

Still see no value in RAID 5?

It is fine to express concerns, and it is finer to advocate more disks.
But it is a little reckless to declare "no value" in something which
would actually provide striping and redundancy with the number of disks
he already has.

You propose instead two mirrored sets and no striping at all. And this
for a database which, without mirroring, but with archivelog, is
ordinarily never going to lose committed data (ie, it has a measure of
redundancy already built in). Don't you think that's a little
BAARF-purist of you? Given that one could always perform a database
recovery if in archivelog mode, why not RAID-0 it and have done?

> After purchasing Oracle and the hardware ... why not get some
> additional disks given the low cost.
>
> Presumably you will want some room for archived log files, etc.

What can we conclude from your post? That four disks is really
insufficient to run Oracle?

But which proportion of the world's installed Oracle base would you care
to guess uses 4 disks or fewer?

Your Boeing background is showing again Daniel: Not all the world is in
that class. And you need to come up with practical advice for the huge
chunk of it that isn't. And RAID 5 should be in that armoury of advice.

HJR

It would be helpful to yourself most of all, and other people
attempting to give advice if you could give some more information about
"what type" of load you expect your oracle database server to be able
to process. Tell us about the applications and their source (oracle,
third party, in house written, etc), the number of concurrent users you
need to support (initially and in the future, etc). What kind of
queries will be running, OLTP or reporting based, simple selects
against mostly single tables, complicated joins, etc. How much
updating versus querying?

How much time do you have to do any benchmarking and possible
reconfiguration of your storage?

With such limited information that you gave initially don't rely too
much on advice from anyone. Most experienced professionals will
strongly caution against implementing RAID 5 from the beginning not
necessarily because it is a solution that will never work it certainly
can in some cases but once you start heading in that direction it is
often difficult if not impossible to obtain necessary downtime to go in
a different direction.