Mark A. Magumba Storage Management

What is storage An electronic place where computer may store data and instructions for retrieval The objective of storage management is to characterize, track and maintain organizational data and data resources Deals with both offline and online data repositories for the purpose of data restoration and archival

Storage Management Process 1.Start the process Data is stored according to its importance and access frequency 2.Data backup, restore and recovery operations Data backups are made on a periodic basis, also restore and recovery plans are made to guide restore and recovery operations required to bring backups online 3.Storage Resource management Involves managing and maintaining those resources on which the backed up data is stored like storage media. The immediately important data is kept in online memory whereas less urgently required data is kept in offline backups and archives and the appropriate security mechanisms are applied

Benefits of storage Management Reduces operational costs of data management and storage Guarantees consistent service levels Enhances customer satisfaction Better alignment of IT processes with business processes

Back up Involves copying information on computer drives to separate drives and can be onsite or offsite Helps to – Keep information securely to ensure minimal data loss in the event of a catastrophe – Reduces computer congestion where backed up data is not immediately important – Reduce the downtime that may result in case of relocation

Types of Backup

Data Repository Model Reflects the particular approach used to backup information – Unstructured data repository model: Here no particular design is followed for instance an individual user saving his files on CDs, external drives and cloud servers as per his convenience without necessarily following a plan. It is convenient for individual users but in a large setting it is extremely inefficient and offers poor recoverability and security – Full + incremental model: A full backup is first done followed by incremental backups. This provides better recoverability and security performance than an unstructured model and also has several restore points

Data Repository Models Continuous Data Protection – Backup is done instantaneously in real time. This is the most secure and complete backup approach but it has huge runtime requirements for instance it will require multiple write heads and real time error checking.

Types of Recovery Recovery refers to retrieving data that may otherwise be lost as a result of a failure. Types of recovery include – Instance recovery: In an environment where there are multiple database instances running if one instance crashes one of the remaining instances can detect this and use the database redo logs to automatically repair the data that had been previously saved by the failed instance – Crash Recovery: This occurs after a single instance database has crashed or every instance in a multi instance database crashes. In order to recover the data you must at least start one instance of the database which then attempts recovery operations on the database

Types of Recovery Media Recovery – This involves extracting data from failed storage media like defective hard drives or damaged tapes using recovery utilities

Space Management The amount of available space is always limited One solution is to remove inactive information from faster memory and transferring it to slower memory This transfer can be done in real time or on a need basis, this is referred to as hierarchical storage management Memory can be organized into a hierarchy depending on its speed, as the figure implies the fastest memory is on top of the pyramid and is usually also the least available

Memory hierarchy

Network Attached Storage Is a file level system data storage attached to a network providing data access to heterogeneous networks Is fundamentally similar to a file server except a file server may provide additional services like mail servers Normally contain one or more disks arranged in logical storage containers or RAID (Redundant Array of Inexpensive Disks) units NAS allows a server to be entirely dedicated to applications rather than having to split its available storage between applications and data as with traditional DAS (Direct Attached Storage) systems

Storage Area Networks Is a dedicated network that provides access to consolidated, block level data They enhance access to storage devices like hard disks, optical juke boxes e.t.c. to make them appear like local storage to the operating system File systems built on top of SANs are able to provide file level abstraction

Additional Benefits of SANs and NAS Sharing of storage simplifies storage administration They also allow more effective disaster recovery processes