HP Volume Shadowing for OpenVMS: OpenVMS Version 8.4 > Chapter 7 Using Minicopy for Backing Up Data (Integrity servers and Alpha)

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.

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%1192.18979.0682.1%
70%1192.18862.6672.4%
60%1192.18724.6160.8%
50%1192.18627.2452.6%
40%1192.18490.7041.2%
30%1192.18384.4532.3%
20%1192.18251.5321.1%
10%1192.18128.1110.7%
5%1192.1871.006.0%
0%1192.188.320.7%