Why Use Minicopy?
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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.
Table 7-1 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 Table 7-1 and Table 7-2 should be used only as an indication of the performance gain you may experience using minicopy.
Table 7-1 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% |
Table 7-2 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 7-2 Comparison of Minicopy and Hardware-Assist (DCD) Copy Performance