e s u y n a r o f e l b i s n o p s e r d l e h e b t o n n a c n o i s s i m m o C e h t d n a , r o h t u a e h t f o y l n o s w e i v e h t s t c e HOGSKOLAN ISKOVDE(HIS) Content createdby: see theIMSdeployedinourMoodle platform. the sources in ELP format (ExeLearning) or enjoy this cisoss.eu content. to Visit download Remember: This is not the best format to l f e r n o i t a c i l b u p . ) s / i 0 h . T 4 / . a n s o - i y s s b i / s m e s PILOT VERSION PILOT m n o e c C i l / n a g r e o p . o s r n u o E m e m h t o c m e o v r i t f a t e r r o c p / / p : s u s p t t h t h i ( w ” l d a e n d o . i n t n u i a f e n r r n e e e t h e t n b I d s e 0 a . n i h 4 a ) t e 8 n k i 5 o l 8 c A 5 n e 1 r o 0 i a - t h a 2 S 0 - m 2 r n o o A f i t n K i u - b 1 e i 0 r h t t S t f E A o - s 1 e - n d 5 o a 1 m 0 m 2 m e ( o b t c C y e a e j v o m i r t p h a c e s i i r h h C T w “ e s u y n a r o f e l b i s n o Backup systems p s e r d l Backup systems e h e b t Content created by: o n n a c HOGSKOLAN I SKOVDE (HIS) n o i s s i m 1. Introduction m o C e Information can be considered more valuable than the hardware that generated it and in many h t d cases irreplaceable. n a , r It is therefore important that it is possible to recover information in case of hardware failure o h t or if files and data gets lost or corrupted for other reasons. u a It can also be the case that there is a need to recover data from some earlier point in time e h t according to an established data retention policy. f o y For these reasons it is important to perform backup on systems. l n o The primary purpose of a backup system is to copy and archive data from computers so that data s w can be recovered. e i v e h t s t c 2. Components of a backup strategy e l f e r The list below shows the essential components of a backup strategy. n o i t a c i Storage l b u Model for data repositories p . ) s / i Storage media 0 h . T 4 / . Processing of data repositories a n s o - i y Choice, extraction, and manipulation of data s s b i / s Management of the backup process m e s m n Goals o e c C i l / Limitations n a g r e o p Implementation . o s r n u Evaluation of the backup-process o E m e m h t o c m e 2.1 Storage o v r i t f a t 2.1.1 Model for data repositories e r r o c p / / p : s u The list below describes different aspects of a model for data repositories. s p t t h t h i ( w ” The model explicates how data are stored during backup l d a e n d Unstructured backup o . i n t n u i a f e For example a number of CDs or DVDs accompanied with some documentation about n r r n e e e t h what was backed up and when the backup was done e t n b I d s e This approach may be the easiest to implement 0 a . n i h 4 a ) It can, however, be difficult to recreate the data in the same way it was stored t e 8 n k i 5 o l Full and incremental backup 8 c A 5 n e 1 r o This approach avoids copying all data every time a backup operation is performed 0 i a - t h a 2 S First, a full backup is performed, thereafter a number of smaller incremental backups are 0 - m 2 r n o o A performed f i t n K i u - b To recover information at a certain point in time: 1 e i 0 r h t t S t Localise the latest full backup taken before the certain point in time, and thereafter f E A o - s 1 e the incremental backups until the certain point in time - n d 5 o a 1 m Continuous backup 0 m 2 m e ( o b Logs every change at the local host at byte level rather than at file level as for full and t c C y e a e j incremental backup v o m i r t p h a Rollback is possible in order to recover information c e s i i r h h C T w “ Writing is performed to another disk (a different computer on the network) when writing to e the "primary" disk s u y n a 2.1.2 Storage media r o f e l The list below describes different relevant storage media used for backup purposes. b i s n o p Magnetic tapes s e r Traditionally the most used medium for backup d l e Offers a good capacity/price quota h e b There are many different variants of magnetic tapes t o It is a sequential medium which implies slow (random) access n n a c Usually writing and reading is fast n o Hard disk i s s i Continuously improved capacity/price quota m m fast access and often easy to use o C External interfaces available (SCSI, USB, Firewire, etc.) e h t Optical disk d n CD/DVD/Blu-Ray etc. a , r o Can be restored from all computers with a compatible reading device h t u Relatively cheap and easy to handle a e May sustain data for 20-100 years (according to the Optical Storage Technology h t f o Association) y l Flash memory n o s USB-sticks, SD, memory stick, etc. w e i Relatively low capacity/price quota v e Good portability between different operating systems and are often considered easy to use h t s t Remote backup c e l Backup to a different storage location via Internet f e r It may be considered an advantage that the backup will be physically separated from the n o i t local disk that was backed up a c i l Potential disadvantages: b u p Internet transmission may become a bottleneck compared to local storage . ) s / i 0 h alternatives . T 4 / . a There may be security issues when transmitting information over the Internet n s o - i y s s b i / s m 2.1.3 Processing of data repositories e s m n o e c C i The list below describes different methods for processing of data repositories. l / n a g r e o p . o s On-line data repository r n u o E This is the most accessible type of data repository m e m h t Information can be recovered within milliseconds (or less) o c m e o Example: hard disk v r i t f a t There is a risk of unintentionally overwriting or deleting information or being subjected to e r r o c p / / virus attacks p : s u s p Near-line data repository t t h t h i ( This type of repository is less accessible compared to on-line data repository w ” l d a Example: Library of magnetic tapes e n d o . i n t n Information can be recovered within seconds or minutes u i a f e n r r n A tape robot can exchange tapes in the recorder e e e t h e t n b I Off-line data repository d s e 0 a . n i Resembles near-line data repository, but requires human interaction in order to make h 4 a ) t e 8 n k storage media accessible i 5 o l 8 c A 5 Information may be recovered within seconds to hours n e 1 r o 0 i a - t h Off-site vault data repository a 2 S 0 - m 2 r n Useful in case of a disaster o o A f i t n K Information is stored at backup media at a different geographical location i u - b 1 e i 0 r h Example: the local office of the system administrator, or a bunker below ground level t t S t f E A o - Backup site data repository s 1 e - n d 5 o Useful in case of a major disaster a 1 m 0 m 2 Information is stored at backup media at a different geographical location m e ( o b t c C y Equipment for recovering the information is kept at the same backup site e a e j v o m i r There is a specific building for the purpose t p h a c e s i i r This is an expensive method for processing of data repositories h h C T w “ 2.2 Choice, extraction, and manipulation of data e s u 2.2.1 Choice and extraction of file data y n a r A central aspect is what information that should be backed up.