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Raw Device Vs ASM? [message #290692] Mon, 31 December 2007 02:12 Go to next message
trantuananh24hg
Messages: 668
Registered: January 2007
Location: Ha Noi, Viet Nam
Senior Member
Hi all!
Wish the best to you in the new year! Happy New Year!

Our RAC still uses Raw Device from 9i, recently, we received an email from the Oracle support which introduced to us about ASM new feature in 10g. As a DBA, I have to learn and take a bit of preparing within them. Read some documents, get some advice from my friends, however, I really understand about this new feature. I think, Raw device is good till now.

Would you like to send me some comments?

We have:
Oracle 9i RAC
HP-UX(PARISC 64bit)
and AIX (64bit)

Thank you!


Re: Raw Device Vs ASM? [message #290696 is a reply to message #290692] Mon, 31 December 2007 02:22 Go to previous messageGo to next message
Michel Cadot
Messages: 64103
Registered: March 2007
Location: Nanterre, France, http://...
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Have a look at this article: http://www.orafaq.com/node/66

Regards
Michel
Re: Raw Device Vs ASM? [message #290707 is a reply to message #290696] Mon, 31 December 2007 03:26 Go to previous messageGo to next message
mkbhati
Messages: 93
Registered: February 2007
Location: Mumbai
Member

Following link can be of some use. Refer page 45 for having nice practice on ASM by emulating files as devices if it is not possible to have real life disk devices available. The Nice thing is that this document covers both LINUX & Windows. ASM is a nice feature but has a learning curve so practice it well using fake devices before using it on production.

http://www.dba-oracle.com/oracle_10g_new_features.pdf

Regards

Manjit Kumar
Re: Raw Device Vs ASM? [message #290713 is a reply to message #290707] Mon, 31 December 2007 04:01 Go to previous messageGo to next message
trantuananh24hg
Messages: 668
Registered: January 2007
Location: Ha Noi, Viet Nam
Senior Member
Thank you, Michel and mkbhati!

I am wondering about the ASM which has one feature: DISKGROUP. What is the performance when adding a disk to DISKGROUP or removing a disk from DISKGROUP.

Re: Raw Device Vs ASM? [message #290726 is a reply to message #290692] Mon, 31 December 2007 05:07 Go to previous messageGo to next message
mkbhati
Messages: 93
Registered: February 2007
Location: Mumbai
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Please Refer Chapter 12 of 10g R2 Database Administrators Guide Topic - Considerations and Guidelines for Configuring Disk Groups.
Hope you will find what you are searching.
So far as performance degradation is concerned while removing or adding disks to diskgroups, I have not observed any potential performance degradation during my last 2 years with ASM. Credit for this goes to efficiency with which ASM does disk rebalancing when you add or remove disks to/from diskgroups.

Regards

Re: Raw Device Vs ASM? [message #291215 is a reply to message #290692] Thu, 03 January 2008 07:09 Go to previous messageGo to next message
gkrishn
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Registered: December 2005
Location: Putty a dark screen
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another thing you should consider should be about redundancy.

You can have redundancy using AMS itself (using FAILURE DISK GROUPS)
or
there is an option to specify EXTERNAL redundancy .

Choice is yours .
Re: Raw Device Vs ASM? [message #291410 is a reply to message #291215] Fri, 04 January 2008 02:14 Go to previous messageGo to next message
trantuananh24hg
Messages: 668
Registered: January 2007
Location: Ha Noi, Viet Nam
Senior Member
gkrishn wrote on Thu, 03 January 2008 20:09

another thing you should consider should be about redundancy.

You can have redundancy using AMS itself (using FAILURE DISK GROUPS)
or
there is an option to specify EXTERNAL redundancy .

Choice is yours .


Thank you for your reply!
Yes! I know about this, and I've configure in my laptop by facing ASM.

And I am considering about:
- Time to migrate (or change) from Raw Device to ASM
- Rewrite some scripts which is scheduled backup (BE scripts)
- How to group the disks that was belonged to raw devices.
- etc..

Have you had any experiences to guide me?

Thank you!
Re: Raw Device Vs ASM? [message #291799 is a reply to message #291410] Sun, 06 January 2008 23:31 Go to previous messageGo to next message
mkbhati
Messages: 93
Registered: February 2007
Location: Mumbai
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Regarding your third point mentioned in above post i.e."How to group the disks that belonged to raw devices." Please do not disturb your existing raw disk setup since it will be quite difficult & tricky to go back to your raw setup once you disturb it & use existing disks for new ASM. I have seen many dba destroying their existing setup while attempting to migrate to a new feature. Please [I repeat please] take some old server for staging (or new if available) & carry out your migration on it with desired ASM configuration, test & debug it thoroughly, if fully satisfied then create a full backup of old database, Now do your migration from staging server to your desired production server.

I know that this will require a service down time window but it is safe than being sorry when you have lost every thing. Another point to note is that you should prefer a manual migration than depending on Oracle tools such as EM or DBUA for migration task as these tools may ditch you down in mid way without telling you the cause of failure. Only thing manual migration requires is that you thoroughly understand the process and you know what you are doing.

Regards



[Updated on: Sun, 06 January 2008 23:32]

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Re: Raw Device Vs ASM? [message #291841 is a reply to message #291799] Mon, 07 January 2008 00:57 Go to previous message
trantuananh24hg
Messages: 668
Registered: January 2007
Location: Ha Noi, Viet Nam
Senior Member
Thank you, mkbhati! Your advicing is very useful!
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