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performance

What would you do with 8 disks?

Yesterday, David Best posted this question at Oracle-L:

If you had 8 disks in a server what would you do? From watching this list I can see alot of people using RAID 5 but i'm wary of the performance implicatons. (http://www.miracleas.com/BAARF/)

I was thinking maybe RAID 5 (3 disks) for the OS, software and
backups. RAID 10 (4 disks + 1 hot spare) for the database files.

Any thoughts?

I do have some thoughts about it.

There are four dimensions in which I have to make considerations as I answer this question:

  1. Volume
  2. Flow
  3. Availability
  4. Change

Just about everybody understands at least a little bit about #1: the reason you bought 8 disks instead of 4 or 16 has something to do with how many bytes of data you're going to store. Most people are clever enough to figure out that if you need to store N bytes of data, then you need to buy N + M bytes of capacity, for some M > 0 (grin).

OS Thread Startup

Recently I encountered a performance problem scenario where a simple sqlplus “/ as sysdba” took about 2minutes to finish, this is critical to the client’s business because they have a local C program that loads Call Detail Reports on the database making use of local authentication for most of its operations and Sql*Loader to load the data, so this “2minutes of waiting” when accumulated greatly consumes significant time on their operations and greatly impacts the business.

When I arrived on the client I first checked the alert logs of both ASM (they have a separate home for ASM) and RDBMS, there were no errors…

Then I checked on the server to see if there were any CPU, IO, memory, swap, and network bottlenecks going on

The CPU run queue was zero and most of the time 90% idle

The disks were also most of the time idle

The memory utilization was low with 430MB free

Security, Forecasting Oracle Performance and Some stuff to post… soon…

I’ve been busy this February “playing around/studying” on the following:

1) Oracle Security products (Advance Security Option, Database Vault, Audit Vault, Data Masking, etc. etc.). Well, every organization must guard their digital assets against any threat (external/internal) because once compromised it could lead to negative publicity, lost revenue, litigation, lost of trust.. and the list goes on.. I’m telling you, Oracle has a lot to offer (breadth of products and features, some of them are even free!) on this area and you just need to have the knowledge to stitch them..

Dang it, people, they're syscalls, not "waits"...

So many times, I see people get really confused about how to attack an Oracle performance problem, resulting in thoughts that look like this:

I don't understand why my program is so slow. The Oracle wait interface says it's just not waiting on anything. ?

The confusion begins with the name "wait event." I wish Oracle hadn't called them that. I wish instead of WAIT in the extended SQL trace output, they had used the token SYSCALL. Ok, that's seven bytes of trace data instead of just four, so maybe OS instead of WAIT. I wish that they had called v$session_wait either v$session_syscall or v$session_os .

Here's why. First, realize that an Oracle "wait event" is basically the instrumentation for one operating system subroutine call ("syscall"). For example, the Oracle event called db file sequential read: that's instrumentation for a pread call on our Linux box. On the same system, a db file scattered read covers a sequence of two syscalls: _llseek and readv (that's one reason why I said basically at the beginning of this paragraph). The event called enqueue: that's a semtimedop call.

Injection Nation

I’m somewhat surprised to see a lack of Oracle blogging reaction to the recent post on The Daily WTF which goes into great detail on a case of SQL injection.  Maybe we’ve either become tired of it or we assume that “my systems don’t do that!”.

So, how do you audit or track if your system is being hit by injection?  How would you detect it?  Assume you’re “just a DBA” — and no one tells you about applications being deployed that talk to the database.  Is there a way you could tell just by looking from within the database?  What kind of assumptions would you make?

The Value of Information

There has been an interesting and somewhat heated discussion going on about a recent blog post by Dominic Brooks and referenced by Doug Burns about the relative value of data vs. applications.  Actually, most of the heat seems to be directed at a comment made by Tim Gorman on several mailing lists in which he states that:

Data, not programs, is the only thing that matters — applications are transient and have no value except to acquire, manipulate, and display data. Data is the only thing with value.

I’ve deliberately taken the quote out of context — for that is how it’s being reacted to, fairly or unfairly on Doug Burns’ blog entry.

I’m not actually going to add any fuel to that fire, only offer up some observations.  I think I agree with many who are stating that data that lies about, unexploited by any application, is a pretty useless waste of storage.  That the true value of data comes from an ability to use it through an application which allows one to analyze, manipulate and visualize information synthesized from the data soup.  One reason I’m excited about the new company I’m with is its focus on helping people increase their ability to exploit their data.