Re: Flash technology based HDD will it make significant difference for OLTP applications?

From: Finn Jorgensen <finn.oracledba_at_gmail.com>
Date: Mon, 7 Jan 2008 10:30:27 -0500
Message-ID: <74f79c6b0801070730q49d3828dj11f98d0d8393d022@mail.gmail.com>


I've implemented a Solid State Disk solution in a previous job, but it was on a MySQL database. This particular application was extremely "database centric" which is to say almost all communication between different pieces of the application was written as calls to the database. Not very efficient, but that's how it goes sometimes when an application is written for a low workload and that workload then grows over time to a level the company didn't think of when they wrote it.

In that case the purchase was made because the company had an immediate scaling problem and did not have the resources to rewrite the application in the immediate future. It was easier just throwing money at HW and it did solve the problem for a while.

Finn

On 1/6/08, krish.hariharan_at_quasardb.com <krish.hariharan_at_quasardb.com> wrote:
>
> I tend to agree and would like to add that the applications I have seen
> over the last 12 years are not IO bound in spite of well tuned SQL but
> primarily because of poorly written SQL statements; SQL statements that read
> or processes more data than is needed to glean the information it wants. At
> the risk of distorting and generalizing at the same time, I would like to
> think that most access paths for OLTP systems are likely to be nested loops
> with index and rowid access paths. To the extent that is true, I would think
> that that data (index particularly) is in the SGA and consequently in "real"
> memory, with the response time component of such an operation bound to the
> disk io only for the duration of a singleton fetch of the data row served
> within15-60ms.
>
>
>
> I am sure there are a number of applications that need sub-sub second
> response times. I wonder if these applications are better served with a
> bigger SGA since I would like to think that for singleton reads the vast
> majority of the time to get the data is in IO call set up and not in
> retrieving the 2-8k block. I must also wonder if an in memory db like times
> 10 or a system such as Gemstone are better suited for these applications
>
>
>
> Long story short, all that rant is about two questions, in my mind
>
> 1. Would that $5k would be a worthwhile spend given today's advancements
> in disk caches and disk technologies vis--vis OLTP systems using a
> conventional RDBMS?
>
> 2. And as Dan indicated below, would it solve the fundamental problem that
> is plaguing the application
>
>
>
> Regards,
>
> -Krish
>
>
>
>
>
>
> ------------------------------
>
> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org] *On Behalf Of *Dan Norris
> *Sent:* Sunday, January 06, 2008 3:11 PM
> *To:* j.velikanovs_at_gmail.com; oracle-l
> *Subject:* Re: Flash technology based HDD will it make significant
> difference for OLTP applications?
>
>
>
> Hi Jurijs,
>
> I don't have any direct experiences to share, but I can say that I have
> talked to a lot of customers about memory-based storage in the past. The
> biggest problem I've seen when memory-based storage is considered is that
> the "solution" is considered before determining what the problem is. That
> is, if you have a CPU bottleneck, then making the storage faster is not
> likely to make a positive impact (in fact, possibly a negative impact).
>
> If storage latency is your primary issue, then making the disk service
> time shorter will likely make a big difference. I'm also interested in
> hearing real-world experiences as I've only talked about this--not
> implemented it. In most of the cases that I've encountered, I ended up
> talking the customer out of making a memory-based storage purchase because
> it wouldn't have addressed the issue that they were trying to solve at the
> time. I always add the caveat that tuning is an iterative process, so it is
> likely that eventually storage will become the bottleneck and it may be
> worth considering such a purchase at that time.
>
>
>
>

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Received on Mon Jan 07 2008 - 09:30:27 CST

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