tape rotation ppt

TAPE ROTATIONSCHEME

Presentation By : S.A Adewale OloyiDate : April 2015

TAPES A tape is a storage device where information

is stored on. It’s an arguably better option to disk.

Why? Life cycleDurability

Ease of UseReliability

Disadvantage Speed !!!

Uncertainty of data integrityShoe-Shinning Effect

Types Of Tapes

Tape Data Cartridge

Tape Cleaning Cartridge

HP MSL 8096

HP MSL 4048

HP MSL2024

Tape Library

Tape Library

IBM Tape Library

Dell PowerVault TL4000

Tape Library

Dell PowerVault

TL2000

Tape Backup Technology

LTO3 LTO4 LTO5 LTO6

Linear Tape-Open (or LTO)

Tape Management Tapes have a long life cycle and durability nonetheless, they should still be managed appropriately for the sake of its contents- Hence, an effective management policyHow?By rotating the tapes

Tape Rotation Strategy Things to consider R.P.O (Recovery point Objective) Number of Tapes Available Off-site Storage Retention

StrategiesFor this presentation, 3 strategies will be discussed. G.F.S (Grandfather- Father- Son) Tower of Hanoi Round Robin

G.F.S Tape Rotation Scheme This is an explanation of the industry-standard Grandfather-Father-Son tape rotation schedule. This backup schedule is appropriate for most small businesses. It is a compromise of protection, convenience and performance

The total number of tapes you will require is based on your desired "restore window". A typical business with a 5-day work week will use a 20-tape rotation that will give them a one-year restore window.

Many, if not most businesses will also keep yearly tapes which can come in

handy for tax reporting purposes. For a 6-day work week ,you will need 22 tapes.

This will allow you to restore files as recent as yesterday and as old as one

year. A 6-month restore window requires 14 tapes

Number of Tapes Required

Tape LabelsDaily Tapes 4 tapes will be used every Monday through Thursday. These tapes will be used every week and will experience the most wear and tear. It is recommended the daily tapes be shifted to the monthly group once in a while so they don't wear out prematurely...like rotating the tires on your car.MondayTuesdayWednesdayThursday

Tape LabelsWeekly Tapes 4 more of your tapes will be used once a month on Fridays. (or Saturdays, depending on whether or not you are backing up a six-day workweek). Whenever it appears you need a Friday Week 5 tape, you should just use the EOM (End of Month) tape.Friday Week 1Friday Week 2Friday Week 3Friday Week 4

Tape LabelsMonthly Tapes Twelve of your tapes will be used on the last business day of each month. January EOM February EOM March EOM etc

Quantity of Tapes

Daily Tapes + Weekly Tapes + Monthly Tapes 4 + 4 + 12

Total = 20 Tapes

A 5-day work week = 20 Tapes

A 6-day work week = 22 Tapes Daily Tapes + Weekly Tapes + Monthly Tapes 5 + 5 + 12

Total = 22 Tapes

Tower of Hanoi

The Tower of Hanoi rotation schedule is widely used.

This schedule can be used in either a daily or weekly rotation scheme. The decision

regarding the frequency of rotation should be based on the volume of data traffic. To

maintain the required history of file versions, a minimum of 5 tape sets should be used in the weekly rotation schedule, or

8 for a daily rotation scheme. . As with the G.F.S rotation scheme, tapes

should be periodically removed from the rotation for archive purposes.

Tower of Hanoi

Tower of Hanoi The Tower of Hanoi rotation

method is more complex. It is based on the mathematics of the

Tower of Hanoi , using a recursive method to

optimize the back-up cycle. So the 1st tape is used every other

day (1, 3, 5, 7, 9,...),

the 2nd tape is used every 4th day (2, 6, 10, ...),

the 3rd tape is used every 8th day (4, 12, 20, ...).

Tower of HanoiA set of n tapes (or other

media) will allow backups for 2 ^n-1 days before the last set is recycled. So, 3 tapes will give 4 days' worth of backups and on

the 5th day it will be overwritten; 4 tapes will give 8 days, and it is overwritten on

the 9th day; 5 tapes will give 16 days, etc. Files can be restored from 1, 2, 4, 8, 16, ..., 2 ^n-1

days ago.

Tower of Hanoi

Tower of HanoiN= NUMBER OF TAPES

WORTH OF BACKUP IN DAYS2** (N-1)

N=3 4 DAYSN = 4 8 DAYSN = 5 16 DAYSN = 6 32 DAYS

N= NUMBER OF TAPES

WORTH OF RETENTION

IN DAYS (2**N) -1

N=3 7 DAYSN = 4 15 DAYSN = 5 31 DAYSN = 6 63 DAYS

Tower of HanoiIn this method, a set of numbered media is used until the end of the cycle. Then the cycle is repeated using media numbered the same

as the previous cycle, but incremented by one. The lowest

numbered tape from the previous cycle is retired and kept

permanently. Thus, one has access to every backup for one cycle, and one backup per cycle

before that.

Tower of Hanoi1ST CYCLE 2ND CYCLE 3RD CYCLE 4TH CYCLETAPE 1 TAPE 2 TAPE 3 TAPE 4

TAPE 2 TAPE 3 TAPE 4 TAPE 5







Observation As you can see, the lower numbered tapes get used far more frequently than higher numbered tapes. This means

that the Tower of Hanoi scheme won't retain daily backups for a

week like the other tape rotation schemes, but it does

give you exponential retention periods.

ObservationFor example, in the 5 tape rotation

scheme, Tape 1 is used 16 times (every other

day). Tape 2 is used 8 times (every 4 days). Tape 3 is used 4 times (with 7 days in

between). Tapes 4 and Tapes 5 are each used 2

times. In essence, this gives you daily and monthly backups like the other tape rotation schemes do, but you use far

fewer tapes in the long run.

Disadvantages of Tower of Hanoi The downside to this rotation

scheme is its complexity and the fact that not all backup applications support

it. This method also has a tendency to

wear out lower numbered tapes because they are used so much more frequently

than higher numbered tapes. Another disadvantage of the method is

that (short retention period)

half the backups are overwritten after only

2 days.

Round RobinRound-Robin is the simplest of tape rotations to understand. This type of cycle uses a single tape set for a set period of time, but only keeps the information for the length of that time period. However, it forces the

Administrator to frequently re-use the tapes over and over again.

Due to wear and tear, these tapes would be replace frequently. Another

con to this type of rotation is that there is no long-term storage

solution.

Round RobinExample: A weekly Round-Robin

tape rotation would mean that there are tapes marked "Monday",

"Tuesday", "Wednesday", etc. Each day’s tapes are used on that

specified day of the week, and then re-used 7 days later

Round RobinOne other simple scheme is to have 5 backup tapes (one for each day of the

work week) and to use each one in succession. This way, you use the same tape every day of the week. For extra

protection, you can use more than one tape for one day of the week, say Friday, and rotate the Friday tape offsite every week. This system pretty much requires that you do a full backup every day. This may be fine for a small business

without a lot of data to preserve, but it can mean a good-sized backup window

every day.

Limitations of Round Robin The biggest problem with the Round Robin variations is that it doesn’t support long-

term data retention, which is very important to have in a data backup plan.

To see why this is important, imagine that an organization uses a 4-week tape

rotation scheme. Now suppose that an organization finds that a critical file has been corrupted. If the corruption occurred more than four

weeks ago, then there are no good copies of

the file that can be retrieved from backup. For this reason, most of the organizations

that use Round Robin also use data archiving.

Recommendations: Small organizations There are many small organizations who can fit all of their data files onto a single tape. Since backing up this small amount

of data does not take much time, many small organizations prefer to do full

backups on a daily basis, and to rotate their tapes in a round-robin strategy.

Assuming there are no actual IT personnel staffed by the company, this

method of daily full backups puts everyone’s mind at ease and does not

require a large collection of tapes. However, keep a couple of spare tapes on-

hand in the event one of them breaks.

Recommendations: Medium organizationsCompanies of this size usually prefer to

implement a G.F.S rotation method. Since this size of organization probably has a

small IT staff, they should all be made aware of how the backup jobs and tape rotations

are implemented. To prevent confusion, the dates of the backups and their associated

tapes should be documented for future reference. The actual backup methods

depends on your needs, but a minimum of the following is recommend… Monthly Full backups, Weekly Incremental backups, and

Daily Differential backups.

Recommendations: Large organizations It is assumed that large organizations will

have a large IT staff. Backup Administrators will be responsible for

managing to a large amount of data which will no doubt be changing very fast. To that end, they will most likely prefer to tighten up the backup jobs to require Differential backups to be performed every couple of

hours, Incremental backups every evening, and Full backups a minimum of once per week. The tape rotation would also be at the Backup Administrators discretion.

Note that any backup system absolutely depends on daily attention and periodic

maintenance. Every backup system requires a

"backup administrator" to change the tapes every day, to store them in the

proper location and to monitor the backup logs for any errors.

Periodically, every backup system needs to be tested in order to be sure data

is actually being backed up and can be restored when needed. Tape drives also need to be periodically cleaned. With most tape drives, this generally means occasionally inserting a cleaning tape.

Reliability

In the end, there is no one single backup tape rotation scheme that

is clearly superior. Each tape data backup scheme has

inherent advantages and disadvantages. It is ultimately up

to you to choose the scheme that is the best fit for your organization's

needs.

Conclusion

THANK YOU

FOR

LISTENING!

tape rotation ppt

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