RE: Re: max parallel query

The real differences between NAS and SAN is how data is accessed - NAS is file-based ("open this file, read that file, lock this other file") while SAN, like direct-attached, is block based ("read block 45345 from disk 7, write block 2442 from disk 3"). SAN runs over Fibre Channel, which is a network protocol that sits under SCSI, while NAS uses NFS (or CIFS, but for Oracle just NFS) over TCP/IP to talk to the storage.

>From a pricing standpoint, its generally true that NAS is cheaper than SAN,
though I can show you a million-dollar NAS box and a 10k SAN. Ditto with performance - while SAN is often faster than NAS, your mileage can vary wildly. Most of the perceived performance gap between SAN and NAS is due to the fact that people have lower standards for their networks than they do their SANs. I've seen people/organizations who would never ever consider using an off-brand Fibre Channel card cheerfully put their performance-sensitive NAS traffic over a $50 Gigabit ethernet card. Intelligent design and careful tuning (plus sizing your storage properly) for your NAS will yield comparable performance to a SAN.

Beyond that, management of NAS vs. SAN is totally different, though I can't get into that in detail here. Finally, the world just changed again with the introduction of iSCSI - SCSI over IP. It's block-based access over traditional IP networks...very exciting stuff.

Thanks,
Matt

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Matthew Zito
GridApp Systems
Email: mzito_at_gridapp.com
Cell: 646-220-3551
Phone: 212-358-8211 x 359
http://www.gridapp.com



> -----Original Message-----

> From: ml-errors_at_fatcity.com [mailto:ml-errors_at_fatcity.com] On 

> Behalf Of DENNIS WILLIAMS

> Sent: Friday, September 19, 2003 11:30 AM

> To: Multiple recipients of list ORACLE-L

> Subject: RE: Re: max parallel query

> 

> 

> Ryan

>    NetApp is in another class of devices labeled NAS for 

> Network Attached Storage. Because its connection with your 

> server runs over a network connection, the performance is 

> very much dependent on the speed and configuration of the 

> network connection. 

>    As has been explained to me, and I very much stand ready 

> to be corrected by others more knowledgeable than myself, 

> there are 3 main classes of storage devices today. They are 

> NAS, Direct-attached, and SAN. My understanding is that NAS 

> tend to be the cheapest and lowest-performance and SAN are 

> the most expensive and highest-performance. But that is just 

> a blanket statement and probably doesn't hold in many 

> specific situations.

>    My personal experience with NetApp is dependent on our 

> configuration and I can't claim that the configuration is 

> perfect. I found the NetApp device to work really well for 

> providing large amounts of storage at a low cost. However, I 

> also discovered that it was really easy to overload the 

> connection. Again, maybe you have a better network 

> connection, I'm just judging by my experience.

>    A standard recommendation for DBAs is to spread I/O among 

> as many devices as possible. I found the performance of our 

> NetApp to be much more acceptable if I could move some high 

> I/O parts of the database to other devices. Redo logs would 

> be a good example of something you might consider putting on 

> any direct-attached disks you have available to you. That 

> would relieve some of the contention over your network connection.

> 

> Dennis Williams

> DBA, 80%OCP, 100% DBA

> Lifetouch, Inc.

> dwilliams_at_lifetouch.com 

> 

> 


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Author: Matthew Zito
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