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pro and cons

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Deanna Tran_1
Frequent Advisor

pro and cons

What are the disadvantage of placing software on the internal disk vs external disk? In addition, how does oracle use the resource ? what is the more effective way to pump uo the i/O rate?
Arockia Jegan
Trusted Contributor

Re: pro and cons

It depends the speed of the drive. If both the drives are having same speed internal disk will give you the good performance.
S.K. Chan
Honored Contributor

Re: pro and cons

It depends on the speed of the IO bus, not so much of weather it's internal or external. A good strategy is always do "load-balancing" as much as you can depending on the type of disks you have (JBOD, AutoRAID, N/W storage, etc) there are various way of achieving finely tuned IO performance. They are the combination of changing the behavior of your OS buffer, disk buffer, kernel parameter tuning, and filesystem/LVM tuning.
Tom Maloy
Respected Contributor

Re: pro and cons

The external drive may be hot swappable.

Oracle won't really care if the disk is internal or external.

With multiple connections to the external storage (eliminates single point of failure), balance the disk usage across the connections.

Using vgextend, you can add primary and alternate paths. For the first pair, use cXdYtZ and cAdBtC. For the second pair, reverse the order to cAdBtC and cXdYtZ.

Just some thoughts...

Carpe diem!
Dave Chamberlin
Trusted Contributor

Re: pro and cons

I would say the external has an advantage in that you can replace/upgrade the disk(s) without loss of service when they are mirrored. Also, you can use vgexport/vgimport to move the disk to another system easily.
Honored Contributor

Re: pro and cons


There are may aspects in this :
1. Looking from the point of view of the operating system
2. Looking from the Oracle side

Internal disks uses the inbuilt SCSI controllers and depending upon the server which you are using and how many disk are installed on the controllers the I/O increases or decreases.

The same way even if you install the oracle on the external disk ( that is the disks in the array ) then here also the same problem is there. Whether you are using fiber channel cards or PCI SCSI cards for connecting the disk array. How many disks are there in the array which are handled by the SCSI controller.

Generally changing the SCSI hhd on the disk array is simple and depending on the array you are using it can be changed online. Many servers do support the online replacement of the internal hdds also. Some arrays have raid 5 configured and hot spare hdd configured and hence the hdd failure may not lead to any downtime.

A. Clay Stephenson
Acclaimed Contributor

Re: pro and cons

Okay, I'm going to be blunt and tell you that it largely does not matter. Long before you start worrying about the performance of the disks, controllers, and CPU's, you need to worry about the code itself. You can tune Oracle and the OS for days and if you are extremely good, you might get a 2X boost (20% is much more likely); if you application is underperforming by a factor of 10, essentially no amount of tweaking (other than fixing the SQL itself) is going to help.

If it ain't broke, I can fix that.
Leif Halvarsson_2
Honored Contributor

Re: pro and cons

To get Oracle performance.
The "classic" metod to get high performance on a database is to distribute the database over several disk. This can be for secutity reasons too and it is still true when using ordinary disks. This needs a well-planned database layout to get equal load on the disks. With RAID disks the controller takes care of the "distribution" and security. To get Oracle performance with RAID:

- Select a RAID disk with high IO-rate (IOPS) rather then high transfer rate.
- Configure the RAID-sets with RAID-level 1+0.
Honored Contributor

Re: pro and cons

Hi Deanna,

just a few points:
- if your internal disks are connected through a slower controller than your external drives, use the external ones
- if the speed is the same, use the disks on the bus with fewer drives
- if the amount of drives is (almost) equal use the faster disks
- if downtime (or uptime) is important to you, use the drives, which are *hot* pluggable
- use the bus where you can stripe over *more* drives

So it all depends ;-)