Keep the following considerations in mind when creating ShadowImage pairs:
- The P-VOL and S-VOL must be the same size.
- Caution: You can copy an encrypted volume to an unencrypted volume. There is no guard logic to enforce copying encrypted P-VOLs only to encrypted S-VOLs. Unless there is a specific reason for the data to become unencrypted, make sure you maintain the encryption by using encrypted S-VOLs.
- If you are concerned with host I/O performance, make sure that the I/O load is light before creating pairs.
- (VSP One Block 85) If you create a ShadowImage pair during Write Same or Unmap command processing, the pair create operation might fail. In this case, wait until the Write Same or Unmap command processing finishes and then create the pair.
- The larger the volume capacity, the longer the time from creation of a pair until it transitions to PAIR status. For virtual volumes, the more pages allocated to a virtual volume, the longer the time from pair creation to PAIR status. Even when no pages are allocated to a virtual volume, if the volume capacity is 256 TB, it takes at least an hour for the status to change to PAIR.
- The value of the T10 PI attribute must be the same for the P-VOL and the S-VOL.
- When you simultaneously create an L1 pair and an L2 pair, if you specify the -split option in CCI, the L2 pair split begins before the L1 pair status changes to PSUS. Because of this, the pair create operation might fail.
- When you create multiple pairs at the same time, the initial copy operations are performed concurrently for up to 24 pairs for VSP One B20 series and 48 pairs for VSP One B85.
If the -split option is specified in the paircreate command, the maximum number of concurrent initial copy operations is 1. If you want multiple pairs to reach PAIR/DUPLEX status, do not specify the -split option.
If the Quick/Steady Split Multiplexing local replica option is enabled, the maximum number of concurrent initial copy operations is 24 pairs for VSP One B20 series and 48 pairs for VSP One B85, even when the -split option is specified.
- For initial copy, the maximum copying multiplicity (the number of jobs used for concurrent copy processing) for each pair is 48, but the number might change to 1 if you specify the -split option for the paircreate command. As the result, copy processing might take longer than when the -split option is not specified. Additionally, if you enable the Quick/Steady Split Multiplexing local replica option, the maximum copying multiplicity is 48 even when the -split option is specified.
- If only the P-VOL capacity of an L1 pair has been expanded, an L2 pair cannot be created. Make sure to create the L2 pair after expanding all of the volume capacities used in the L1 pairs.