Re: Out of morbid curiosity - can you straddle datafiles using Filesystem + ASM DGs

On 6/20/19 5:15 PM, Chris Taylor wrote:
> I'm mainly just curious as we need to move a 100TB database to ASM and
> have limited storage capacity and was wondering if this would be an
> option.

Well, that depends on the ASM redundancy. To move 100TB db to ASM with external redundancy, you need at least 100TB storage. With normal redundancy, it's at least 200TB and with abnormal redundancy (does anyone remember "Young Frankenstein"?) , it's at least 300 TB. You can also move 100TB database to 20 TB storage, but you would have to do a lot of "TRUNCATE" and "DROP" commands which are usually not highly regarded by the business owners of the database.

>
> Where you would have the ASM DGs available to the DB and datafiles on
> Filesystems.
> Then slowly move datafiles (alter database datafile move) over to the
> ASM diskgroups and reclaim the filesystem volumes as we free them up.
>
> Again, this is really out of morbid/technical curiosity more than
> anything.
>
> Chris

There is another option, called "ACFS" which also runs on top of ASM and technically satisfy all of your requirements. You can have data files on ACFS and non-ACFS file systems, in the same database.

-- 
Mladen Gogala
Database Consultant
Tel: (347) 321-1217


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