Re: RMAN/Oracle SE/RDS

Yes, thanks. Excellent responses. Just what I was looking for.

On Thu, Aug 1, 2024 at 11:26 AM Amit Grover <amitgrover27_at_gmail.com> wrote:

> +1 to what Tim said above about backups in general and would like to add a
> few details about AWS RDS. I work for AWS RDS so know a few things on how
> RDS RDS has put together backups for recoverability, hope it helps.
>
> AWS RDS uses AWS EBS(Elastic Block Store) as block storage, RDS also has a
> Block level replication technology that is running behind the filesystem
> that does write to a second Availability Zone(AZ) before the write is
> acknowledge on the AZ1 so that your StandardEdition(SE) database has high
> availability that you would normally get from Data Guard on EE.
>
> AWS RDS can also do cross region backup replication so you can do cross
> region restores for SE databases for DR and also have HA in the same region
> bcas of being able to RDS MAZ(MultiAZ) deployments. Point in time
> recovery(PITR) is also Managed by AWS RDS by restoring the storage level
> Snapshot and then replaying the archives to recover the database to the
> point in time requested.
>
> For more details on how AWS EBS Snapshots work see
> https://docs.aws.amazon.com/ebs/latest/userguide/ebs-snapshots.html
> More details on AWS RDS MAZ: https://aws.amazon.com/rds/features/multi-az/
> Cross region automated Backups with AWS RDS:
> https://aws.amazon.com/blogs/database/managed-disaster-recovery-with-amazon-rds-for-oracle-cross-region-automated-backups-part-1/
>
>
> Best Regards
> Amit Grover
> 2065966629
>
>
> On Thu, Aug 1, 2024 at 8:39 AM Tim Gorman <tim.evdbt_at_gmail.com> wrote:
>
>> Ethan,
>>
>> I wrote and supported the extensions to Azure Backup for Oracle databases
>> (HERE
>> <https://learn.microsoft.com/en-us/azure/virtual-machines/workloads/oracle/oracle-database-backup-azure-backup?tabs=azure-portal>),
>> so I feel capable of answering some of the questions here, as well as any
>> specific questions on Azure.
>>
>> First of all, there are essentially two basic methods for performing
>> database backups...
>>
>> 1. streaming
>> 2. storage-level snapshots
>>
>> RMAN falls squarely into the category of "streaming", where the files
>> comprising an Oracle database backup are copied from one location to
>> another. Later on in the process, those "backup sets" can be streamed
>> again to another location (i.e. vault) for redundancy and data protection,
>> or streamed yet again to another geographic location as well for additional
>> protection and disaster resilience.
>>
>> Storage-level snapshots, like Azure Backup, are based on the storage
>> being able to designate a point-in-time at which a snapshot is "frozen"
>> while modifications continue to occur. I'm not referring to the old-style
>> "mirror splits" originating 30+ years ago, but rather copy-on-write or
>> redirect-on-write technology originating and perfected in the past 20
>> years. Later on in the process, those media snapshots can be streamed to
>> another location (i.e. vault) for redundancy and protection, and still
>> later the media snapshots can be streamed to yet another geographical
>> location (i.e. another cloud region, etc) for further redundancy and
>> disaster resilience.
>>
>> It is important to understand where in the technology the streaming
>> occurs, and where (and how) snapshots occur.
>>
>> It is also important to understand the metrics by which recoverability
>> must be measured...
>>
>> 1. recovery point objective (RPO)
>> - also described as "*point-in-time to which recovery is expected*"
>> 2. recovery time objective (RTO)
>> - also described as "*expectation for the amount of time for
>> return-to-service*"
>>
>> In general, backups by Oracle RMAN can recover with RPO=0 or RPO near
>> zero, but RTO can be problematic due to the time it takes to stream data
>> from and to the database files.
>>
>> In general, backups using storage-level snapshots can also recover RPO=0
>> or RPO near zero, and RTO can be extremely quick if the local snapshot
>> image can be used. If the snapshot image must be restored from a local
>> vault, then RTO increases dramatically (because of the streaming restore
>> from the vault). It should be noted that there are few circumstances where
>> the local snapshot image cannot be used, but they certainly exist.
>>
>> One of the advantage of Oracle RMAN are more advanced features like
>> corruption checking and file-level or block-level restores; storage-level
>> snapshots are generally an all-or-nothing type of restore.
>>
>> One of the advantages of storage-level snapshots, especially Azure
>> Backup, is that the entire VM image is backed up, not just the database.
>> So cloning a copy of the entire running VM with its database(s) is
>> incredibly easy, to the point where some of "advantages" of Oracle features
>> become moot. For example, while Azure Backup can only restore the entire
>> database, it is fast and easy to restore the entire database to a new
>> cloned VM, copy what is needed back to the original VM, and then destroy
>> the clone VM when finished with it. LIkewise, a temporary cloned VM can
>> easily be employed to perform BACKUP VALIDATE CHECK LOGICAL operations to
>> find corrupted database blocks, or as test images for various uses. One
>> nonsense objection I've heard to that is: "but cloning VMs is so
>> expensive", which just isn't true compared to the hours and days spent
>> running a single RMAN restore. A clone VM doesn't have to use the same VM
>> shape as the original; it can be much less expensive, and for a few
>> dollars, a clone VM can accomplish more in an hour or two of existence than
>> a DBA will spend in wages through days of figuring things out.
>>
>> Twenty-five or so years ago, I was one of those promoting Oracle RMAN,
>> trying to get DBAs to leave aside their beloved manual backup scripts. The
>> fact remains that Oracle RMAN is irrevocably based on the concept of
>> sequentially streaming backups to tape, even though nobody uses tape-based
>> media any longer. It should be noted that Oracle RMAN must be integrated
>> to a "virtual tape library" (i.e. NetBackup, Networker, etc) using an SBT
>> driver, and that terminology alone should be convincing. RMAN is the
>> epitome of streaming sequential database backup technology, but it is
>> indeed firmly grounded in extinct technology. If you think about it, the
>> concept of "incremental backups" central to RMAN are themselves
>> accommodations to the limitations imposed by streaming sequential media,
>> and as everyone knows, "incremental backups" only save time during backup,
>> and add time and complexity during restore. RMAN does a fine job of
>> disguising that complexity during restore, but it is still present.
>>
>> I could continue blathering on, for there is so much to discuss in pro's
>> or con's, but I'll stop for now...
>>
>> Hope this helps?
>>
>> Thanks!
>>
>> -Tim
>>
>>
>>
>> On 8/1/2024 6:46 AM, Ethan Post wrote:
>>
>> Managing a customer with SE and single threaded RMAN backup. They take a
>> lot of time to run and of course a lot of time to restore. If I was going
>> to optimize I would look for another file copy/split mirror or even more
>> old school manual scripted solution.
>>
>> I am fairly certain restores are faster in RDS which leads me to think
>> they are not using RMAN. I do believe OCI Database Service uses RMAN and
>> wondering if they allow parallel or something when it is SE in the cloud
>> with their service.
>>
>> Not sure what Azure does but would like to know if anyone has any
>> helpful links to video overviews of Azure/Oracle backups and recovery/cross
>> region.
>>
>> If the above is all roughly accurate then one could put a plus in the
>> "cloud" column in terms of 1) You can run SE and 2) The backup and restore
>> process is likely going to be faster and more powerful (cross region). At
>> least that is my opinion for the moment with the information I have which
>> is limited.
>>
>> Would like to hear your thoughts here. What is the $ value one should
>> factor in when considering on prem cost to hosted cloud if we factor in
>> backup/restore capabilities?
>>
>>
>>

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