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
| 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% |
