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Why Use Minicopy?  



The minicopy operation can be used at the discretion of the system manager and at a time chosen by the system manager.

Because minicopy can significantly reduce the time it takes to return a member to a shadow set, it gives system managers greater flexibility in scheduling the removal and return of a shadow set member, and it improves availability.

The time needed to perform a minicopy is proportional to the amount of change that occurred to a shadow set in the disk's absence. A shorter copy time gives sites more flexibility in managing backups.

Comparison of Minicopy and Full Copy Performance shows the results from one series of tests, comparing full copy and minicopy times for shadow sets over a spectrum of write activity. The results presented in Comparison of Minicopy and Full Copy Performance and Comparison of Minicopy and Hardware-Assist (DCD) Copy Performance should be used only as an indication of the performance gain you may experience using minicopy.

Table 1   Comparison of Minicopy and Full Copy Performance
Percentage of Bits Set Time for Full Copy (seconds) Time for Minicopy (seconds) Minicopy Time as Percentage of Full Copy Time
100%
4196.09
3540.21
84.4%
90%
3881.95
3175.92
81.8%
80%
3480.50
2830.47
81.3%
75%
3290.67
2614.87
79.5%
70%
3194.05
2414.03
75.6%
60%
2809.06
2196.60
78.2%
50%
2448.39
1759.67
71.9%
40%
2076.52
1443.44
69.5%
30%
1691.51
1039.90
61.5%
25%
1545.94
775.35
50.2%
20%
1401.21
682.67
48.7%
15%
1198.80
554.06
46.2%
10%
1044.33
345.78
33.1%
5%
905.88
196.32
21.7%
2%
712.77
82.79
11.6%
1%
695.83
44.90
6.5%

Comparison of Minicopy and Hardware-Assist (DCD) Copy Performance shows the results from another series of tests, comparing performance times of a hardware assisted copy (using MSCP disk copy data (DCD) commands on an HSJ controller) with a minicopy over a spectrum of write activity.

Table 2   Comparison of Minicopy and Hardware-Assist (DCD) Copy Performance
Percentage of Bits Set DCD Copy Time (seconds) Time for Minicopy (seconds) Minicopy Time as Percentage of DCD Copy Time
100%
1192.18
1181.61
99.1%
90%
1192.18
1097.03
92.0%
80%
1192.18
979.06
82.1%
70%
1192.18
862.66
72.4%
60%
1192.18
724.61
60.8%
50%
1192.18
627.24
52.6%
40%
1192.18
490.70
41.2%
30%
1192.18
384.45
32.3%
20%
1192.18
251.53
21.1%
10%
1192.18
128.11
10.7%
5%
1192.18
71.00
6.0%
0%
1192.18
8.32
0.7%


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