RE: Sizing - RAC, storage subsystem EMC

Mogens - Now you're getting the entrepreneurial spirit! The other idea would be to follow in Cary's footsteps and detail your knowledge in a book. That automatically increases your credibility. :-)

    Seriously, that has been one of my complaints. We need a Configuring Hardware for Oracle book. There have been a few attempts. Alomari is the latest one as far as I know. Just a glossary of technical choices and what they mean to a DBA would be a good starting point. I think there are a couple of pitfalls:

• Include comparative results. Is RAID5 10 percent slower? 20? Under what types of loads?
• Don't base all results on batch benchmarks but on simulated real loads. Remember the days when raw was loudly touted? Couldn't be beaten on batch benchmarks. But few production sites found it worth the trouble.
• Balance performance with vulnerability. If a tradeoff costs a little performance but makes failure less likely is good for me. Or makes recovery more straightforward. I note the thread on backing up online redo logs has a lot to do with making the recovery foolproof. My boss may never notice a 5% reduction in performance, but a crash sure gets his attention. And a bungled recovery could cause him to pop an artery. Or me. Maybe this book isn't practical, but I figure -- wish large, buy what I can get.

Dennis Williams
DBA, 80%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Sunday, May 25, 2003 11:57 PM
To: Multiple recipients of list ORACLE-L

I finally see my error. Why do I keep having high blood pressure about RAID-5/RAID-4/RAID-53/RAID-S decisions? Doesn't make sense...because:

More RAID-5 -> more performance and availability problems -> more performance and availability work -> more money to consultants -> higher profit -> more money to company owner -> sex & power to company owner

Best regards,

Mogens Nørgaard
co-owner of Miracle A/S (a consultancy which specializes in performance and availability problems)

DENNIS WILLIAMS wrote:

Rachel - You make some excellent points. I am speaking to the situation

where the site doesn't have a performance problem. When there is a problem,

everyone is much more eager to accept suggestions.

      As you point out, the DBA usually doesn't buy hardware, so the

hardware people tend to take that as intruding on their responsibilities

with the intent of making them look bad. So they react defensively. And for

every reason you can quote that RAID5 is bad, they will provide a

countervailing reason why your information isn't valid. At least not with

their hardware configuration. And the hardware vendor is very helpful in

giving them information that will bolster their arguments. Then again, your

average DBA usually isn't a foremost expert in disk configurations.

        A consultant that is paid to come in and solve a performance problem

then leave doesn't face the longer-term issues that arise from making ones

colleagues look bad. My point is that there are some battles one wouldn't

want to win.

Dennis Williams

DBA, 80%OCP, 100% DBA Lifetouch, Inc.

dwilliams_at_lifetouch.com <mailto:dwilliams_at_lifetouch.com>

-----Original Message-----

Sent: Friday, May 23, 2003 8:27 PM

To: Multiple recipients of list ORACLE-L

Here's the thing. Disks are cheap. Maybe. But buying 5 disks is still

cheaper than buying 10 disks. And it is NOT the people who actually

work with the disks (DBAs, Sysadmins, even developers) who have the

authority to order the disks.

You need places and floor space to put the disks as well. It's not like

you can just hang them from the ceiling.

And even more so these days, and it seems most especially in the US

companies, companies are trying to cut costs to the bone (we just went

through an exercise where we practically had to jump through hoops just

to get more memory for a production system which obviously needed the

memory). And cutting costs means as few disks as possible, means reuse,

consolidate and do without.

It kind of reminds me of one of the sayings my parents (who grew up

during the Great Depression here) have told me of that time: "use it

up, make it do, or do without"

we're in the "do without" phase

Rachel

• Mogens_Nørgaard <mailto:mln_at_miracleas.dk> <mln_at_miracleas.dk> wrote:

I'm beginning to think that we're having this wonderful discussion

about

RAID-5 time and again because the vendors keep coming up with

arguments

to prove that the general laws of nature don't apply to this

particular

technology.

In the 50s we had a prime minister here in Denmark that said to the

assembled parliament: "If that's the facts, then I deny the facts".

Somehow you have to admire a guy like that.

Since disks are now cheap, how on Earth is it that we allow various

IO-vendors to bundle cheap disks, expensive cache which we won't

need,

and stupid technologies like RAID-5 into a box called SAN/NAS or

whatever and charge 42 billion units of some real currency for it?

Why don't we take our swords and shotguns and AK-74s (that's the

small

calibre), and point them at them until they actually just bundle a

bunch

of inexpensive disks into RAID 1+0 which we ALL know is superior to

RAID-S, RAID-5 (notice how S looks like 5 - it's no coincidence).

It's

superior to RAID 0+1 even. It doesn't require (the expensive) cache

either.

One of my wonderful experiences was with a TelCo here, where the

vendor

kept saying that they should of course just add cache if performance

wasn't sufficient. When they finally reached the 32GB (yep,

thirty-two

giga-bytes) of cache alone, they gave up, ripped the stuff apart and

reconfigured it as RAID 0+1 and it finally performed on the small

writes. We all loved it - except possibly the disk-vendor, who kept

saying RAID-<some letter that resembles the number 5> was of course

fantastic, and that they shouldn't listen to all these bitter, old,

twisted Oracle people who just hated RAID-5 and the likes ... ahhh...

just because!

It's got nothing to do with Oracle or not. It's got to do with money

and

brains.

RAID 1+0 is the best you can buy.

RAID 0+1 is almost as good.

RAID 5 sucks - in all its disguises and permutations - compared to

0+1

or 1+0.

If RAID-5 is good enough for you, fine. But remember to test the

good,

old restore of the backup and time it so that you're prepared if it

happens. It should of course take about four times as long as the

backup.

As Connor said (and Cary has said it in his excellent, but futile,

RAID-5 paper) it's when you really, really need disk performance that

RAID-5 will let you down.

Yo.

Mogens

Arun Annamalai wrote:     

Hi George.  

I would recommend go with Raid 5 and its not that one transaction

triggers that many writes as you have mentioned/calculated.

It is all buffered with recovery mechanism.  

Have you thought about Raid4(Network appliance) hardware. (I am no       

way     

affliated with Network appliance, except that we use in our site.)

Most of the big names use them, such as

1, Yahoo. (you can see network appliance logo when you logout of       

your     

yahoo email account)

2. Oracle

3. Southwest airlines.  

I mean Yahoo, Southwest Airlnes are all heavy transaction oriented

shop on a given per minute interval.

The most common overhead of SAN is that the throughput of the       

switch     

that connects your server to the san storage.  

Also, heard that Net App (best in NAS) is colloborating with       

Hitachi     

(best in SAN storage) to get the best technology for storage and

thoroughput performance. But this might take a while or might       

already     

be in the market. Check out with your local Hitachi or Netapp

representatives.  

Hope this helps.

-Arun.  

• Original Message -----

    From: George.Leonard_at_za.didata.com
<mailto:George.Leonard_at_za.didata.com>

      <mailto:George.Leonard_at_za.didata.com> <mailto:George.Leonard_at_za.didata.com>

    To: Multiple recipients of list ORACLE-L

      <mailto:ORACLE-L_at_fatcity.com> <mailto:ORACLE-L_at_fatcity.com>

    Sent: Tuesday, May 20, 2003 2:06 AM

    Subject: Sizing - RAC, storage subsystem EMC

    Hi all, hope you can give some input ideas.      

    I am in the process of designing a system for a client of ours       

for     

    a proposal      

    The sizing information I have been given is as follows.      

    58.1 million tickets/day at 351 bytes per record. The record       

was     

    complete populated (all columns filled to max) in a table and       

then     

    analyzed. Average row size 351 bytes.

    =~ 19 GB/day. Raw data. Plus overhead (indexes, temp space,

    rollback, some other data etc) here and there I have requested       

5 TB.           

    We need to keep records for a month. Table design I am looking       

at     

    is a date partition with a second level hash partition. This is       

so     

    that I can move data in the oldest week/table space off line       

and     

    write them to optical storage for possible retrieval at a later

    date (requirement).      

    Of course this will be on locally managed table spaces with       

auto     

    storage management for segments.      

    Hardware:

    The database will be a Oracle RAC 9.2.0.4 on Sun cluster 3       

build     

    on 2 x Sun StarFire V880, 4 CPU's, 4 GB RAM each,

    Connected to an EMC SAN via Fiber Channel      

    I do not have more information about the EMC array at the       

moment.     

    Hitachi has been mentioned. (excuse the spelling)      

    Question I have.      

    I have been asked how many writes the Database will be doing to

    the SAN per second.

    I have determined that I should expect about 2000       

tickets/second.     

    The table in question will have 2 indexes.      

    Now following rough guessing I said I should expect at least 16

    000 writes/second      

    This was done by say/assuming      

    2 writes for the redo log files (2 members)

    2 writes for the control files (2 control files)

    2 writes to index blocks

    1 write to undo table space block       

• message truncated ===

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