Managing Space - Recovery Appliance / ZDLRA / RA - 1 of 6 - Attributes Helping Define Storage


Introduction

In this First Part of a series of blogs on ZDLRA/RA backup storage, I am going to share some of my insights into Managing Backup Storage/ZDLRA Space/ZDLRA Storage on Oracle "Zero Data Loss Recovery Appliance" (ZDLRA) also referred to as the “Recovery Appliance” (RA). To keep it simple RA or ZDLRA are used through out this blog.  All references to backups are related to Oracle Database backups only. This blog also assumes you have a basic understand of Oracle Database Backup and Recovery and RA/ZDLRA Administration.

This blog is specific to understanding, where opportunities exist over and above the storage management automation integrated into the RA, and when needed, help the RA Admin better understand overall backup storage on the RA and manage storage from a database backup and recovery perspective. With this in view the content herein has been kept at a higher level of analysis and limited to known tuning capabilities available to an RA Admin.

While I have tried to share my personal insights in this blog, Oracle Documentation and MOS (My Oracle Support) Notes, should still be your primary source of content and references on this subject. Any queries provided in this blog are not supported by Oracle.

What is not covered in this blog, is REPLICATION or SBT USAGE and Enterprise Manager Cloud control (EMCC) RA Storage management capabilities.

Content in the series will be covered under the following with the highlighted focused in current blog.


Content [Click On Link]:

Attributes Helping Define Storage:


A good starting point on Backup storage, would be understanding how the RA utilizes user definable attributes to meet Oracle database backup and recovery storage needs. The RA does a lot more under the seams and it is best not to start taking control until and unless where needed. Understanding your Oracle Database Backup Storage requirement, and early detection of storage needs, can help form a healthy storage practice. More details on attributes in Figure 1-1, and how they impact the way storage is allocated and managed for backup and recovery are discussed below.

Figure 1-1 Metrics Defining Storage Allocation

 
zdlra storage



Figure 1-2, below shows a visual representation on the dependencies of some of the crucial attributes discussed above in helping balance the Storage and Recovery needs. While RWG is essential to Business data/database Recovery, Reserved Space ensures RWG gets the storage it needs to meet these recovery goals. Optionally Max Disk Retention (MDR) allow flexibility to retain additional backups over and above RWG if there is storage to spare i.e. meet audit needs, few days of buffer etc.

Figure 1-2 Storage Allocation & Purge – Key Concepts

zdlra storage


To review in more detail, starting from the bottom:

            BLUE BOX (Figure 1-2): Consists of a Shared/Central Storage Pool, is distributes into:

1.    "FREE SPACE", which is usable storage not allocated, available for consumption and not part of any backup at the time data was read.
2.     “Freespace Goal” is an RA specific non-tunable attribute/pool that tracks the total storage space in GB needed for incoming backups based on the last trends. This is currently calculated every 3 Hours for backup data collected over the last 6 hours. Tracking this over multiple time periods to capture a MAX Storage required helps identifying the peak storage needed i.e. Seasonal large backup vs evenly balanced.
3.   “System Purge Space” (SYSTEM_PURGE_SPACE), not represented here is required for internal PURGE activities by the RA is managed internally with not user control capability. The storage needs are generally very small.

RED BOX (Figure 1-2): Per-Database, Allocated & Used Space/Storage is assigned for each key attribute starting from Recovery window Goal to Reserved Space and Disk Retention.  

1.  “Recovery Window Goal” (RWG) is a Goal defined as Seconds/Minutes/Hours/Days enabling Point In Time (PIT) recovery to any point within the defined Window. The underlying storage required varies according to the backup volume/size (L0, L1 and Realtime Redo/Archive Loags) received and factors like deduplication & compression. This attribute is defined within a PROTECTION POLICY on the RA.

2.   “Max Disk Reserved Space” (MDRS) also referenced to as “Disk Reserved Space” or “Reserved Space” is the physical storage in GB set aside or allocated for a single database to meet the RWG. If not set this defaults to 2.5x Database Size. It is a good practice to set this above the RWG storage needs i.e. 10-20% above RWG storage. The Sum Total of Reserved Space cannot exceed the Usable Capacity of the RA.

3.    “Max Disk Retention Window” (MDR) is the total number of Days (RWG + Retention) that a backup will be retained on Storage within the RA i.e. 7 days of RWG + 7 days of Retention = 14 Days of MAX Retention Window. MDR is based on storage availability outside of RWG. If not set this defaults to 2x RWG. Ideally you want to have 1.5 x or minimum of 5 days between RWG and MDR. It is essential to keep in mind that MDR can be purged down to RWG to reclaim storage for Free Space or Freespace Goal.  

4.      “Guaranteed Copy” is an RA attribute that controls how the RA manages deletion of existing (oldest/earliest) Backups to release/free up storage for incoming/new backups. Ideally best to leave this unset. Setting this attribute to (For more details refer to Oracle ZDLRA Admin Guide):

a.      “YES” – Never purges a backup before it has been copied to tape or replicated
b.      “NO” -- RA can purge backups before they have been copied to tape or replicated

Summary:


Hopefully after reading this blog you have some understanding of the various attributes that are available to identify how Oracle Database Backup Storage is managed.

Going through the Next blogs in this series hopefully may help identify and better manage some of the storage and capacity planning outside of  what the RA already does and help the RA better manage user recovery requirements.    

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