Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
1995-12-29
2002-06-11
Yoo, Do Hyun (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C714S005110
Reexamination Certificate
active
06405294
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to data center migration, and more specifically to a platform for migrating computer mainframe applications and volumes of data from a source Direct Access Storage Device (DASD) to a remote target DASD.
2. Related Art
Businesses that offer technology, such as telecommunications, must deal with the necessity of collecting, storing, and managing large volumes of data on a daily basis. It is common for such companies to utilize several mainframe computers located in various facilities known as data centers.
These data centers are strategically placed in geographical locations, taking into consideration such aspects as data network topology, user proximity, local real estate markets and economy, local employment base, and survivability of natural disasters. Often, strategic direction requires a company to move a data center from one location to another, which consists of moving all data of a source mainframe to another remote target mainframe. Data to be moved includes system configuration, operating system, applications, support, and user data. Sometimes an entire mainframe is to be moved, while other situations dictate that only certain applications be moved.
In essence, moving a mainframe from one location to another consists of migrating data from a source Direct Access Storage Device (DASD) to a target DASD. These DASD units are physical devices used for permanent storage on mainframe computers. They store all data that are used by a mainframe computer, and, thus all data that must be moved as part of a data center migration. Therefore, a data center migration is essentially a migration of data from one DASD to another.
Migrating such large volumes of data requires several provisions to minimize business impact. Some aspects that must be considered are:
(i) Data integrity: Moving large volumes of mission-critical data exposes the business to data corruption. In addition to exposures due to the physical transfer of data, updates and changes made to data during the move may not be reflected at the target location;
(ii) Minimal application downtime: A business cannot be put on hold for the extended periods of time required for traditional data migrations. Minimizing application downtime during the move is critical for the users of the data center;
(iii) Cost: The cost of resources needed for a data center migration is a fundamental business concern. Minimizing the cost of resources such as data center equipment, transportation vehicle, and data transfer network is essential;
(iv) Manpower: People resources represent another cost of a data center migration. Minimizing the headcount needed is always a concern; and
(v) Time: Reducing the amount of time needed for a data center migration reduces such liabilities as resource/manpower costs, application downtime, and data integrity exposures.
There are three (3) traditional methods of data center migration: Tape Backup and Ship, Tape Drive Channel Extension, and Physically Moving DASD Units.
a. Tape Backup and Ship
The Tape Backup and Ship method consists of backing up to tape all data on the source DASD. This is also known as tape dump-and-restore. All data on the source DASD are downloaded to magnetic tapes. The tapes are then shipped by truck, rail, or air to the site of the target DASD. When received, the tapes are loaded onto the tape drive of the target mainframe and all data are uploaded to the target DASD.
This method obviously requires a large number of magnetic tapes. For every one gigabyte (G.B.) of data to be migrated, approximately two (2) tapes are needed. This means for a typical migration of 2500 G.B., 5000 magnetic tapes are required.
Another major disadvantage of this method is the fact that customer applications must be down for the entire time it takes to download the data to tape, ship the tapes, and then upload the data to the target DASD. Table 1 below shows the approximate time (in minutes) it takes to backup data from a source DASD to tape, transport the tapes, and then restore the data to a target DASD. Time is indicated as a function of gigabytes to be migrated, and assumes eight (8) tape drives are used. An estimate of twelve (12) hours is used for transport time, assuming cross country air freight is used.
TABLE 1
Total
Total
Gbs
Backup
Transport
Restore
Minutes
Hours
100
200
720
200
1120
18.67
500
1000
720
1000
2720
45.33
1000
2000
720
2000
4720
78.67
1500
3000
720
3000
3000
112.00
2000
4000
720
4000
4000
145.33
2500
5000
720
5000
5000
178.67
One important disadvantage of this method is that all customer applications are inaccessible during this time. For example, during the migration of a data center consisting of 1000 G.B. using the Tape Backup and Ship method, all applications are down for approximately 3.28 days.
Another disadvantage of this method is the resources and associated costs needed to conduct the migration. Extra manpower is needed to perform the tape download and upload, and to physically move the tapes. Transportation of the tapes may incur significant costs, especially if it is over great distances and requires expedited delivery. Also, as indicated in Table 1 above, the cost of tapes may be high if a large amount of data is to be migrated.
Another disadvantage of this method is its exposure to data corruption. Due to the fact that the tapes serve as an intermediate medium, data may be corrupted during the downloading or uploading of data to and from the tapes. There also exists the possibility of tapes being lost or damaged during transportation and many exchanges of hands, or at least of tapes being placed out of sequence. Finally, unplanned application updates that are made during or after the source DASD download may not be reflected at the target DASD.
b. Tape Drive Channel Extension
The Tape Drive Channel Extension method consists of connecting a channel extender unit to the source mainframe tape backup system. The source mainframe treats the channel extender as a tape drive and writes data to the extender as data is being read from the source DASD. The channel extender unit then sends this data over a DS-3 Data Link connected to the target tape drive which writes the data to tapes at the target data center. The tapes must then be manually uploaded to the target DASD.
As with the Tape Backup and Ship method, this method obviously requires a large number of magnetic tapes. For every one (1) gigabyte (G.B.) of data to be migrated, approximately two (2) tapes are needed. This means for a typical migration of 2500 G.B., 5000 magnetic tapes are required.
Also as with the Tape Backup and Ship method, customers applications must be down and inaccessible for a significant period of time. Applications must be down during the backup (source mainframe writes DASD data to a channel extender unit,) and restore (tapes are uploaded to a target DASD) processes. However, there is no tape transport time needed, and the restore process may begin approximately one (1) hour after the backup process begins. Table 2 below shows the approximate time (in minutes) it takes to backup data at the source data center, and to restore data at the target data center. Time is indicated as a function of gigabytes to be migrated, and assumes eight (8) tape drives are used.
TABLE 2
Total
Total
Gbs
Backup
Transport
Restore
Minutes
Hours
100
250
—
60
310
5.17
500
1250
—
60
1310
21.83
1000
2500
—
60
2560
42.67
1500
2750
—
60
3810
63.50
2000
5000
—
60
5060
84.33
2500
6250
—
60
6310
105.17
As with the Tape Backup and Ship method, all customer applications are inaccessible during this time.
Another disadvantage of this method is the resources and associated costs needed to conduct the migration. Extra manpower is needed to perform the restore process at the target site. Also, as indicated in Table 2 above, the cost of tapes can be high if a large amount of data is migrated.
Finally, due to the fact that both tapes and channel extender units are serving as intermediate media, data may be corrupt
MCI Communications Corporation
Portka Gary J.
Yoo Do Hyun
LandOfFree
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