Both Thin Image and Thin Image Advanced back up data by managing differential data as snapshots. Thin Image Advanced, which uses data reduction shared volumes, can provide faster backup than ShadowImage (which requires physical copy), and has lighter load on storage performance than Thin Image.
ShadowImage copies the entire volume (not only differential data). Although it is time consuming, ShadowImage has an advantage. ShadowImage is tolerant of a physical failure, such as a drive failure.
| Item | Thin Image Advanced | Thin Image | ShadowImage |
|---|---|---|---|
| Effect on storage performance | Has a low load on storage performance. Write data from a host is not overwritten to the data of when the pair was split and written to a different location. Therefore, data copy is not required. | Has a high load on storage performance because data copy is required every time data is written by a host. Write data from a host is overwritten to the data of when the pair was split. | If a host writes data to an area for which the data has not yet been copied to the S-VOL, the data needs to be copied to the S-VOL, which might cause a performance load. |
| Speed of replication | Requires a short time because meta data is copied fast during the initial copy. | Requires a short time because the initial copy is not required. | Takes time because the initial copy is required. |
| Maximum number of replications | 1,024 | 1,024 | 9 |
| Capacity efficiency of replication | The capacity efficiency is good because the difference with the P-VOL is written to the pool. (The capacity efficiency is better than Thin Image because deduplication and compression is applied to the differential data in Thin Image Advanced.) | The capacity efficiency is good because only the differential data for the P-VOL is copied. | The capacity efficiency is not good because the entire P-VOL is copied. |
| Use of replication | Cannot be used separated from the P-VOL. | Cannot be used separated from the P-VOL. | Can be used separated from the P-VOL. |
| Physical failure of the P-VOL | If a physical failure occurs in the P-VOL, data in the S-VOL cannot be guaranteed because the S-VOL shares data of the P-VOL. | If a physical failure occurs in the P-VOL, data in the S-VOL cannot be guaranteed because the S-VOL shares data of the P-VOL. | The P-VOL can be restored by the use of the S-VOL. |
| Physical failure of the S-VOL | Data in the S-VOL is not guaranteed. | Data in the S-VOL is not guaranteed. | Data in the S-VOL is not guaranteed. |
| Relationship between pair volumes and the pools | The P-VOL and S-VOL need to be created in the same pool. | The P-VOL and S-VOL can be created in different pools. The P-VOL does not need to be created in a pool. | The P-VOL and S-VOL can be created in different pools. Both the P-VOL and S-VOL do not need to be created in pools. |
| Physical failure of a pool | If a physical failure occurs in a pool, data in all P-VOLs and S-VOLs in the pool is not guaranteed. | If a physical failure occurs in a Thin Image pool, data in all S-VOLs in the pool is not guaranteed. If the pool is shared by the P-VOLs and S-VOLs, data in all P-VOLs and S-VOLs is not guaranteed. | If a physical failure occurs in a pool for P-VOLs, data in the relevant P-VOL is not guaranteed, but data in the S-VOLs is guaranteed. If a physical failure occurs in a pool for S-VOLs, data in the relevant S-VOL is not guaranteed, but data in the P-VOL is guaranteed. |
| Capacity depletion of a pool | When a pool is full, data in the P-VOLs and S-VOLs is guaranteed due to inflow control. | When a pool is full, data of all S-VOLs in the pool is not guaranteed.1 | When a pool for the S-VOLs is full, data of all S-VOLs in the pool is not guaranteed. |
| Media that can be used for a pool | Flash media2 | Flash media and HDD | Flash media and HDD |
Notes:
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