Re: ASM Question/Suggestions - moving from 10TB devices to 20TB devices and diskgroup move

Sorry, missed the list in my reply.

Yes, doing it in one command is the best approach. It rebalances the data only once.

https://docs.oracle.com/en/database/oracle/oracle-database/19/ostmg/alter-diskgroups.html#GUID-6BB31112-8687-4C1E-AF14-D94FFCDA736F

> You can add, resize, or drop disks while the database remains online.
> Whenever possible, multiple operations in a single ALTER DISKGROUP
> statement are recommended. Grouping operations in a single ALTER DISKGROUP
> statement can reduce rebalancing operations.
>

There will be no rebalance at all if you resize the existing disks (option 1 in my previous email). It is possible if you use the same storage. Of course, you have to drop the extra disks that you don't need which roughly rebalances just a half of data.

On Wed, 8 Sept 2021 at 15:28, Chris Taylor <christopherdtaylor1994_at_gmail.com> wrote:

> Ok, so I think I'm following and that makes sense.
>
> In a nutshell it would be add all the new 20T devices *AND* drop the
> existing 10T devices in the same command so that the rebalance only
> rebalances to the 20T devices?
>
> Is that the theory/idea?
>
> That would definitely prevent the need to use rman to move the datafiles
> or anything.
>
> Chris
>
>
> On Wed, Sep 8, 2021 at 10:09 AM Mikhail Velikikh <mvelikikh_at_gmail.com>
> wrote:
>
>> Hi,
>>
>> I know ASM devices should be the same size when you rebalance.
>>>
>>
>> If it is an EXTERNAL redundancy disk group, then you can have a disk of
>> different size there.
>> 12c ASM: Unable To Add New Disks With Dissimilar Size To 12.1.0.2 ASM
>> Diskgroups (Normal or High Redundancy) Due To ORA-15410 (New 12c ASM
>> Enhancement Validation/Constraint) (Doc ID 1938950.1)
>> <https://support.oracle.com/rs?type=doc&id=1938950.1>
>> Although it is not a best practice, it can be used during such migrations.
>>
>> Is that the *only* option here? Anyone have additional
>>> suggestions/thoughts?
>>>
>>
>> 1. You can resize the existing disks online, then drop the disks you
>> don't need.
>>
>> https://docs.oracle.com/en/database/oracle/oracle-database/19/ostmg/alter-diskgroups.html#GUID-6AEFFA72-7BDC-4AA8-8667-8417AAF3DAC8
>> It didn't work for me two years ago with AFD. I haven't encountered the
>> same issue with ASMlib or without any Oracle drivers.
>> If you don't use AFD, ignore notes below:
>> Cannot resize ASM Disk using ASM Filter Driver(AFD) online (Doc ID
>> 2099164.1)
>> ASM not displaying resized disk size in AFD configuration (Doc ID
>> 2263094.1)
>> Bug 29893839 - ASM CRASHES WHEN RUNNING AFD_REFRESH AFTER THE LUN RESIZE
>> AT OS LAYER (Doc ID 29893839.8)
>>
>> 2. You can provision new 20TB LUNs and DROP/ADD disk in one ALTER
>> DISKGROUP command. ASM automatically rebalances data.
>>
>> https://docs.oracle.com/en/database/oracle/oracle-database/19/ostmg/alter-diskgroups.html#GUID-14E48E96-F5D6-4F41-A8E4-B535CBD3CAE5
>>
>> Best regards,
>> Mikhail Velikikh
>>
>>
>>
>> On Wed, 8 Sept 2021 at 14:46, Chris Taylor <
>> christopherdtaylor1994_at_gmail.com> wrote:
>>
>>> List,
>>>
>>> We have a need to restructure our underlying ASM devices to 20T from 10T
>>> to reduce the number of luns assigned to a host.
>>>
>>> The Total DiskGroup SIze is 163840.00 GB (~ 160 TB) made up of 10TB
>>> devices. (16 Devices)
>>>
>>> Our storage admins would like to move these to 20T devices and halve the
>>> number of physical devices presented.
>>>
>>> I know ASM devices should be the same size when you rebalance.
>>>
>>> I know *one* option is to add the 8 20T devices as candidates and create
>>> a new diskgroup and move the data to the new diskgroup and then drop the
>>> old 10T devices from ASM.
>>>
>>> Is that the *only* option here? Anyone have additional
>>> suggestions/thoughts?
>>>
>>> Chris
>>>
>>>

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