Better backup and recovery with snapshots.Go back fifteen years and poll IT managers on their number one problem and they'd say "backup and recovery." Ask them the same question today, and the answer is the same. This reigning champ of IT problems has a new challenger that is promising to upset traditional thinking and finally put the issue of backup and recovery to rest. The challenger is snapshots. On their own, snapshots offer an efficient quick-restore capability, but when combined with networked storage and the best practices in today's backup systems Noun 1. backup system - a computer system for making backups ADP system, ADPS, automatic data processing system, computer system, computing system - a system of one or more computers and associated software with common storage , the result is a revolution of elegance. What is a Snapshot (1) A saved copy of memory including the contents of all memory bytes, hardware registers and status indicators. It is periodically taken in order to restore the system in the event of failure. (2) A saved copy of a file before it is updated. ? Snapshot is the user-friendly word for point-in-time copy (the terms are interchange-able). A point-in-time copy represents an exact duplicate of a data volume at the moment the copy was created. Subsequent changes to the data volume do not affect the point-in-time copy. At any future date, one can restore the data from the point-in-time copy. The clever part is that these duplicates don't actually take up any additional hard-drive space. Only the changes that occur after you take the snapshot are stored. Data that remains unchanged is only stored in one place and is referenced by both the baseline volume and the point-in-time copy. The granularity The degree of modularity of a system. More granularity implies more flexibility in customizing a system, because there are more, smaller increments (granules) from which to choose. of the stored changes is at the block level (the smallest chunk of data that a disk system can work with), so this results in a very space-efficient method for creating restorable copies of data. The principal application of snapshots is to provide a quick backup-and-restore option. Any given volume can have multiple snapshots representing different time slices A short interval of time allotted to each user or program in a multitasking or timesharing system. Time slices are typically in milliseconds. (operating system) time slice in the history of the data volume, and the taking of snapshots is a nearly instantaneous in·stan·ta·ne·ous adj. 1. Occurring or completed without perceptible delay: Relief was instantaneous. 2. procedure. If a problem occurs that requires a recovery operation, the system can be restored to a previous snapshot. The restoration procedure is also very quick, as the volume is brought offline and the snapshot brought online--a process often referred to as rollback A DBMS feature that reverses the current transaction out of the database, returning the data to its former state. A rollback is performed when processing a transaction fails at some point, and it is necessary to start over. See two-phase commit. . Unlike traditional tape or disk-to-disk backup restorations, snapshot rollback does not require that the data be "unpacked" from a special backup format by being run through a backup server A computer in a network used to store copies of files from client machines or other servers. Such servers typically have their disks set up in a RAID configuration to provide fault tolerance. See backup program, RAID, SAN and LAN free backup. . The snapshot image is the original disk image--what the operating system operating system (OS) Software that controls the operation of a computer, directs the input and output of data, keeps track of files, and controls the processing of computer programs. expects to see. This greatly improves recovery times. Snapshots are co-located with baseline volumes, meaning they reside in the same storage system and are protected with the same data-protection features such as RAID and redundant controllers. However, the snapshots also are vulnerable if the primary storage systems should somehow fail. As they stand alone, snapshots cannot replace traditional tape backup Using magnetic tape for storing duplicate copies of hard disk files. Users can add an internal or external tape drive to their desktop computers for backup purposes, and files are typically copied to the tapes using a backup utility that updates on a periodic schedule. and recovery; however, they can vastly improve them. [ILLUSTRATION OMITTED] Backup Windows The "backup window" problem results from the traditional approach to backup. Application servers traditionally stream data to a tape device. For many applications, this backup operation can take many hours. During the backup, the application might not be able to provide normal service. In cases where the application is still providing service, its performance will be degraded de·grad·ed adj. 1. Reduced in rank, dignity, or esteem. 2. Having been corrupted or depraved. 3. Having been reduced in quality or value. , as the backup involves moving a large amount of data to the tape device. This period during the backup is referred to as the backup window. Most businesses have constraints CONSTRAINTS - A language for solving constraints using value inference. ["CONSTRAINTS: A Language for Expressing Almost-Hierarchical Descriptions", G.J. Sussman et al, Artif Intell 14(1):1-39 (Aug 1980)]. on how long the backup time can last. This varies from a few hours in the early morning to only a few minutes. In addition, this small window of opportunity reduces the frequency of backups, which in turn reduces the recovery options. How Snapshots and Networked Storage Work Together Networked storage decouples the storage devices from the servers and interconnects them over a storage area network (SAN). SANs allow the application servers and backup servers to see the same disk storage systems. When coupled with snapshots, this visibility into the storage enables a new form of backup and recovery. Here's how it works: The application server takes snapshots of its volumes. The backup server then mounts the snapshots and copies them over the SAN to tape devices. The tapes can then be moved offsite to a secure location. In the end, the application server operates uninterrupted during the backup process. The application server is completely unhindered unhindered Adjective not prevented or obstructed: unhindered access Adverb without being prevented or obstructed: he was able to go about his work unhindered during the backup operation. In addition, the backup server and tape libraries can operate all of the time, eliminating the backup window problem. Understanding Snapshots and Application Interactions Applications play with their data like children play with their toys. The application starts and opens up its data files and then throws the data all over the place in memory and on disk. When the application is finished (unlike children) it puts the data away in a nice clean format, so that it can quickly resume work once restarted. With snapshots, the data is captured in a disordered state. Application recoveries from this state are not always successful. This concept is called "snapshot consistency", and a snapshot that is taken in this way is considered an inconsistent snapshot. The solution is to make the application aware of the snapshot process. In this case, the application briefly flushes dirty buffers of data to disk before the snapshot is taken. Some coordination occurs between the application and the storage device, such that the snapshot is taken at the right moment. The application remains online and continues its normal services while this process is underway. All of this happens in a matter of a few seconds and then the snapshot is taken. The result of this coordination with the application is an application-consistent snapshot. This snapshot image is good as gold and can be copied to tape for safe keeping. A New Paradigm New Paradigm In the investing world, a totally new way of doing things that has a huge effect on business. Notes: The word "paradigm" is defined as a pattern or model, and it has been used in science to refer to a theoretical framework. Today's operating systems Operating systems can be categorized by technology, ownership, licensing, working state, usage, and by many other characteristics. In practice, many of these groupings may overlap. , applications and storage arrays are integrating more and more snapshot coordination capabilities, simplifying the deployment and management of snapshots with backup and recovery. The promise of snapshot technology and better backup and recovery is here, as it finds its way into every storage management toolkit and becomes established as a standard data center function. Peter Hunter Peter Hunter (1746 – 21 August 1805) was a British Army officer and colonial administrator. Hunter was born to a landed gentry family in Perthshire, Scotland. In 1767 he entered the British Army by purchasing an Ensign's commission. is product marketing manager at EqualLogic, Inc. (Nashua, NH) www.equallogic.com |
|
||||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion