Oracle-L: RE: SAN configuration for Banner

From: Sam Bootsma <sbootsma_at_gbrownc.on.ca>
Date: Thu, 20 Nov 2003 10:10:02 -0800
Message-ID: <F001.005D7470.20031120101002@fatcity.com>

I agree with you on point 4 - and the SA here also confirms that the Manager has his facts wrong on this point.

I haven't seen much here in terms of quantitative measurement of IO - I can ask around. I'd like to do DBA work, but they have me working on an Data Architecture project (which is great experience), so I have no time to be a DBA.

Cary Millsap's paper "Is RAID 5 Really a Bargain", states that RAID 5 is three times more likely to incur data loss than a RAID 1 Array. A date says it is Jan. 3, 2000 - so almost 4 years ago. I don't know if this is still true today or not. But I would also be interested in more details on this.

Thanks!

Sam.

-----Original Message-----
Sent: November 20, 2003 7:44 AM
To: Multiple recipients of list ORACLE-L

I *think* but I may have entirely misread the comment that point 4 is just wrong. It sounds like you only have one raid 5 set (which is shared between 2 machines). If this is the case then the clustering has no effect on the fault tolerance/performance of the raid 5 set. Or am i just on crack here?

Point 5. writing to the datafiles *may* be acceptable on a raid5 set (it just depends what the volume of write activity is - does anyone have any idea what the IO requirements will be? if so do the calculations), writing to redo/archive almost certainly won't be. I'd hold out for Raid 1 for the logs and maybe compromise on Raid 5 for the data.

as for the last point, I'd also like to see the justification for raid5 is 3 times more likely to suffer dataloss. I'm afraid that a) I don't think I believe it and b) you've got the logs anyway :( OK just a) really.

corrections and clarifications welcome.

You may also wish to look at James Morle's SANE SAN paper at www.oaktable.net it would appear to be pertinent (and he does know whereof which he speaks)

Niall

	-----Original Message-----
	From: ml-errors_at_fatcity.com [mailto:ml-errors_at_fatcity.com] On
Behalf Of Sam Bootsma
	Sent: 19 November 2003 15:55
	To: Multiple recipients of list ORACLE-L
	Subject: FW: SAN configuration for Banner

	Hi List,

	 

	We are approaching the cusp of a decision on how to store Oracle

data files on our SAN. We don't have the SAN yet, but it is due to arrive any week (if not any day).

I passed Cary's "Is RAID 5 Really a Bargain?" paper to our Sys Admin, which he read and succinctly summarized for the Technical Manager here. I have also read through a couple of papers referenced in the BAARF site. The Sys Admin comments were:

Dell would like to know what RAID mode we want configured on the SAN for the B80 and 6C4 computers. Sam has told me that, in the Oracle community, mirroring (RAID1) is preferred over RAID 5 for various reasons (RAID5 is: more costly for write-intensive applications, 3 times more likely to incur data loss, suffers from massive performance degradation during partial outages). RAID1 will be more costly per unit of usable storage. Mirroring seems to be the best choice. Let me know what you think.

Here is the Manager's response:

Any suggestions on how I can counter points 4 and 5 - and the last point before his "Thanks" line? Currently we have two B80's (AIX 4.3.3) set up in a HA configuration. They share an external disk array. So if a hardware component in the primary box fails, then it will automatically failover to the secondary box (and at the same time, the secondary box takes control of the external disk array). I think the clustering term in point (4) is referring to this setup.

Thanks for any suggestions.

Sam.

	Sent: November 18, 2003 5:08 PM
	Subject: RE: SAN configuration for Banner

	 

	All the points are valid...however..my thought processes were as

follows:

The System & Core Application disks are resident on the disks within the CPU and Mirrorred (Everyone OK with that I think)
The Databases are Resident on the SAN
The SAN disks are RAID 5 as the provide more usable space for the cost as compared to mirrorring
As the IBM Systems (B80's & 6C4's) are clusterd thus effectivley Mirrors the RAID 5 Arrays mitigating the issues Sam raises re preformance degradation (which will only ever arise in the event of a failed disk/automated rebuild which is usually configurable to address performance degradation)
Write to Disk/Commit to Database should be a background process (although I recognise this is a transaction/write intensive based system)

This is a standard model that all servers are being deployed with and unless there are any specific technical reasons why this will not work it is the way I would like to see the systems implemented. Remeber, with the SAN...Reconfiguration of Disks is not a large issue anymore if required in the future.

Although not an AIX/Oracle guy...I disagree with the statement that RAID5 is 3 times more susceptable to incur Data Loss. RAID 5 is a proven technology

Thanks..... Andrew

		-----Original Message----- 
		From: Carl Nowak 
		Sent: Tue 18/11/2003 2:56 PM 
		To: Andrew Riem 
		 Subject: SAN configuration for Banner

		 

		Dell would like to know what RAID mode we want

configured on the SAN for the B80 and 6C4 computers. Sam has told me that, in the Oracle community, mirroring (RAID1) is preferred over RAID 5 for various reasons (RAID5 is: more costly for write-intensive applications, 3 times more likely to incur data loss, suffers from massive performance degradation during partial outages). RAID1 will be more costly per unit of usable storage. Mirroring seems to be the best choice. Let me know what you think.

Carl

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Author: Sam Bootsma
INET: sbootsma_at_gbrownc.on.ca

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