HP XP P9500 Storage - Manual (Page 48)

2. Searches for the oldest time stamp from the previous step, then restores data up to that
time to the secondary volumes.
In the example shown in figure, the oldest time stamp is 15:00. Continuous Access Journal
Z restores all data that have a time stamp 15:00 or earlier to the S-VOLs.
◦ For Journal 1, Continuous Access Journal Z restores all data up to 15:00.
◦ For Journal 2, Continuous Access Journal Z restores all data up to 14:02.
◦ For Journal 3, Continuous Access Journal Z restores all data up to 14:03.
◦ For Journal 4, Continuous Access Journal Z restores all data up to 14:04.
•
Consistency time. Remote Web Console displays the consistency times of EXCTGs, journals,
and pairs in the Continuous Access Journal Z windows.
◦ The consistency time of an EXCTG is the latest time stamp of the restored data in the
group in which consistency is guaranteed.
In the example shown above, the consistency time of the EXCTG is 15:00.
◦ The consistency time of a journal is the latest time stamp of the restored data.
In the example figure, the consistency times of journals 1 to 4 are as follows:
– The consistency time of Journal 1 is 15:00.
– The consistency time of Journal 2 is 14:02.
– The consistency time of Journal 3 is 14:03.
– The consistency time of Journal 4 is 14:04.
◦ The consistency time of a pair is the latest time stamp of the data that has been restored
when the pair becomes suspended.
In the example figure, if a pair in the journal 1, 2, 3 or 4 is suspended immediately after
data are restored, the consistency time of the pair is as follows:
– If a pair in Journal 1 is suspended, the consistency time is 15:00.
– If a pair in Journal 2 is suspended, the consistency time is 14:02.
– If a pair in Journal 3 is suspended, the consistency time is 14:03.
– If a pair in Journal 4 is suspended, the consistency time is 14:04.
If a failure occurs in a primary system, restore journal data with time stamps later than the
consistency time of the EXCTG, to the S-VOLs.
In the example figure, the consistency time of the EXCTG is 15:00; therefore, you must restore
the following data to S-VOLs:
◦ Data with the time stamp 15:02 in journal 2.
◦ Data with the time stamp 15:03 in journal 3.
◦ Data with the time stamp 15:04 in journal 4.
If a failure occurs in a secondary system, compare the consistency times of all journals in the
EXCTG, identify the oldest consistency time, then restore all data with time stamps later than
the oldest consistency time, to the S-VOL.
In the example figure above, the consistency time of journal 2 is the oldest among journals 1
to 4. Since the consistency time of journal 2 is 14:02, you must restore the following data to
S-VOLs.
◦ Data with the time stamp 15:00 in journal 1.
◦ Data with the time stamp 15:02 in journal 2.
48 Using extended consistency groups