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Re: raid level

From: Mladen Gogala <gogala_at_sbcglobal.net>
Date: Fri, 16 Dec 2005 08:29:20 GMT
Message-Id: <pan.2005.12.16.08.29.20.109139@sbcglobal.net>


On Fri, 16 Dec 2005 09:19:42 +0100, Sybrand Bakker wrote:

> On 15 Dec 2005 22:36:16 -0800, "ORA600" <panandrao_at_gmail.com> wrote:
> 

>>Hi,
>>
>>As much as i would like to agree with all on this post about RAID 0+1
>>or 1+0, there is one caveat you have to consider...
>>
>>the no.of arms or disks available to your application(and Oracle) for
>>servicing read/write requests is cut to half with RAID 0+1. These days,
>>you can get 300 GB disks and a Terabyte worth of data can sit in about
>>6-8 disks! If you are running a r/w intensive application, no amount of
>>IO balancing can help..because you don't have anything to balance! just
>>3-4 disks will be servicing all the needs of the application, don't
>>even bother about the no.of users.
>>
>>the key is IOps/seconds. What the peak and sustainable IO rate that the
>>SAN box or disk system provide? what are the needs of your application?
>>how does it access the data? predominantly reads or writes, etc.?
>>
>>Whereas with RAID 5, you can have 70% of your disks servicing your
>>read/write requests. I have seen many IO intensive application use RAID
>>5 successfully and with S.A.M.E technology. You have to get it right,
>>then it works for you. There is, of course, a well documented slowness
>>in write thoroughout when you compare it with RAID 0+1.
>>
>>For your 2.2 TB SAN Box, you would surely have some cache. I would
>>suspect 6-8GB may be available. So, that also needs to be considered.
>>
>>Good luck!
>>
>>cheers
>>anand
> 
> 
> This is truely a sad post. Yet another advocate of 'throwing iron at
> the problem' ie symptom fighting, instead of curing the problem.
> 
> If you have a R/W intensive application, and the customer doesn't want
> to resolve the problem (because the app has been developed by an
> incompetent 3rd party vendor), NOTHING can help you, only PRAYER,
> there is some justice  in Heaven (and the customer will suffer so
> badly, he can't deny the facts anymore)

Sometimes, given the price of HW, hardware upgrade is cheaper then a good DBA/performance analyst and it does make the most of sense from the commercial point of view. If better performance can be achieved by spending additional $10,000 for a box, why bother with consultants? Application themselves have limited age and have to be rewritten almost from scratch every few years. If the application is technologically out of date, written by using Forte, Jam or some other "application generator", then letting it run on a stronger box might carry the company until the complete rewrite in Java or .NOT can be financially justified to the senior management. I'm sorry to say, but it's all economy. Buck is driving everything.

-- 
http://www.mgogala.com
Received on Fri Dec 16 2005 - 02:29:20 CST

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