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

>
> 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.
>

I would add that we could use the WAIT clause for that: https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlrf/ALTER-DISKGROUP.html#GUID-22D73AB6-7063-4627-A2ED-18D521ED2557

> Use this clause to specify when, in the course of the rebalance operation,
> control should be returned to the user.
>
> -
>
> Specify WAIT if you want control returned to the user after the
> rebalance operation has finished. You can explicitly terminate a rebalance
> operation running in WAIT mode, although doing so does not undo any
> completed disk add, drop, or resize operations in the same statement.
>
> e.g. (ADD/DROP/REBALANCE in one command):

> ALTER DISKGROUP "<name>"
> ADD DISK '<path>' NAME "<name>"
> DISK '<path>' NAME "<name>"
> DROP DISK "<old_disk>"
> DISK "<old_disk>" *REBALANCE POWER 11 WAIT*
>
> Or we can use it in a separate rebalance operation too:
https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlrf/ALTER-DISKGROUP.html#GUID-22D73AB6-7063-4627-A2ED-18D521ED2557

[image: image.png]

On Wed, 8 Sept 2021 at 16:09, Mark J. Bobak <mark_at_bobak.net> wrote:

> 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
>>>>>
>>>>>

--
http://www.freelists.org/webpage/oracle-l





image/png attachment: image.png