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

I agree with Mikhail. That is how I've done it in the past, and it worked well.

NOTE: Make *sure* the rebalance is *complete* before attempting to remove the old LUNs! In other words, be sure that V$ASM_OPERATION is empty before proceeding to remove the old device from the server.

-Mark

On Wed, Sep 8, 2021 at 10:51 AM Mikhail Velikikh <mvelikikh_at_gmail.com> wrote:

> 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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