Re: Oracle ASM and High Availability

From: Sanjay Mishra <"Sanjay>
Date: Wed, 24 Feb 2016 19:35:35 +0000
Message-ID: <436340411.9675674.1456342535622.JavaMail.yahoo_at_mail.yahoo.com>

Seth
Thanks for the update. 
So what you meant to say that If i loose one Disk from ASM DG which has around 100 Disk, then we cannot drop the fault disk from the Disk group if it has the data. Secondly What I meant with Second question is that if we can drop the disk from DG which is faulty in External REDundancy and can bring the DG up. Problem was that I saw the env which 11 Database sharing same DG and after one Disk was damaged then all database has to be restored by recreating the new DG after clearing all disk header. Sanjay

    On Wednesday, February 24, 2016 2:11 PM, Seth Miller <sethmiller.sm_at_gmail.com> wrote:  

 Sanjay,
>> 1. Can I drop this disk and bring the Diskgroup up ?If the disk group is normal or high redundancy and there is at least one complete failure group after dropping the disk then yes, it can be dropped.
If the disk group is external redundancy then no, you cannot drop any disk because data is striped evenly across all devices. The exception would be if there were no data on the disk.

>> 2. Can I recover the Database once the DG is mounted  instead to restore multiple Database ?I'm unclear as to what you are asking here. If you are asking if all databases in a disk group have to be restored, the answer is no. You could just restore one of the databases.

Seth Miller

On Wed, Feb 24, 2016 at 12:54 PM, Sanjay Mishra <smishra_97_at_yahoo.com> wrote:

Seth
I can understand that playing with kfed/amdu is really scary thing and ust want to play on my personal laptop now to get well versed with outputs and commands. Quick question, that if I had multiple database sharing same diskgroup and lost the disk in the diskgroup then1. Can I drop this disk and bring the Diskgroup up ?2. Can I recover the Database once the DG is mounted  instead to restore multiple Database ? TSanjay

    On Wednesday, February 24, 2016 10:35 AM, Seth Miller <sethmiller.sm_at_gmail.com> wrote:  

 Sanjay,
Although this is probably not the answer you are looking for but, at the point you are describing the best way is to engage Oracle Support. There are a number of good articles on using kfed/kfod and manual disk repair, and the ASM SMEs at Oracle are really smart and willing to share their information but, once you start messing with the disk header, you are deep in the weeds and certainly unsupported without the direct involvement of Oracle Support.

Seth Miller
On Wed, Feb 24, 2016 at 9:27 AM, Sanjay Mishra <smishra_97_at_yahoo.com> wrote:

Seth
If header is not repairable then what is the best way to bring environment back with less downtime. Scenario is Disk group is 20Tb and Lost disk is 512G. TIA Sanjay

    On Tuesday, February 23, 2016 3:29 PM, Seth Miller <sethmiller.sm_at_gmail.com> wrote:  

 Sanjay,
There are ways to fix corrupt ASM disk headers (other than restoring a backup of the header) so no, it is not true that all the data would be lost if external redundancy disk header is lost. However, this scenario is exactly why you would not use external redundancy of you are unable to protect the disks and the headers at the storage layer. There are scenarios where you would have separate disk groups for each database but these would generally not be for protecting data, but segregating it for purposes of using storage snapshots.

Seth Miller
On Tue, Feb 23, 2016 at 10:48 AM, Sanjay Mishra <dmarc-noreply_at_freelists.org> wrote:

Hi 
Need some expert opinion on Oracle ASM best practices and high availability. It is recommended to have minimum DG using ASM like DATA/FRA for multiple database on the Cluster. Now I had seen some scenario, where one disk header on External Redundancy DG causes to restore all Database and hence Major failure. Does this not make sense to create multiple DG like DATA for each Database and FRA can be shared ? Please share your opinion and just for reference that Disk header in such scenario was not recoverable from backup header. TIASanjay           

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Received on Wed Feb 24 2016 - 20:35:35 CET