Background
Most of cloud service providers support archive storage, and some even support deep archive storage to help users reduce storage costs. Archive and deep archive objects cannot be accessed directly and must be restored before being migrated.
Validity Period
After archive or deep archive objects are restored, they can be accessed directly for a specified validity period. Beyond this period, restored objects will automatically return to the archive or deep archive status.
By default,
- Archive objects restored by RDA are valid for three days.
- Deep archiveobjects restored by RDA are valid for five days.
Restoration Time
It takes some time to restore archive and deep archive objects.
The following table lists the time required by different cloud service providers for restoring archive and deep archive objects. This is for reference only. The actual restoration time is also affected by the constraints of cloud service providers.
Cloud service provider |
Archive Data Restoration Supported |
Time for Archive Data Restoration |
Deep Archive Data Restoration Supported |
Time for Deep Archive Data Restoration |
Description |
|---|---|---|---|---|---|
Microsoft Azure |
Yes |
1 hour |
No |
N/A |
|
UCloud |
Yes |
≤ 15 minutes |
No |
N/A |
N/A |
QingCloud |
No |
N/A |
No |
N/A |
N/A |
AWS |
Yes |
1 to 5 minutes |
Yes |
≤ 12 hours |
For all but the largest archived objects (250+ MB), data that is accessed by using expedited retrievals is typically made available within 1 to 5 minutes. |
Baidu Cloud |
Yes |
≤ 30 minutes |
No |
N/A |
N/A |
Kingsoft Cloud |
Yes |
1 to 10 minutes |
No |
N/A |
N/A |
Huawei Cloud |
Yes |
1 to 5 minutes |
In OBT |
3 to 5 hours |
The restoration time of deep archive objects is affected by the size and amount of data to be restored. |
Qiniu Cloud |
Yes |
5 minutes |
Yes |
12 hours |
The restoration time may vary depending on the object size. |
Tencent Cloud |
Yes |
1 to 5 minutes |
Yes |
12 to 24 hours |
A maximum of 100 QPS can be made for data restoration. |
Alibaba Cloud |
Yes |
Several minutes |
Yes |
|
|
Precautions
- The preset restoration time displayed on the migration task page is based on the longest possible time required by cloud service providers, as displayed in Table 1. It is for reference only.
- The restoration time of ultra-large objects may exceed the longest possible time. As a result, these ultra-large objects may fail to be migrated because they may not have been restored when the migration starts. You are advised to use the restoration tools provided by the source cloud service provider to restore these objects before migrating them using RDA.
Exceptions
The following are the possible reasons for migration failures of archive or deep archive objects when the automatic restoration function of RDA is enabled.
- Archive or deep archive objects to be migrated have not been restored after the preset restoration time is used up.
- Restored objects return to the archive or deep archive status during the migration because their validity periods of restoration have expired.
Solution:
Click Restart, and RDA will automatically restore the archive or deep archive objects that failed to be migrated and migrate them again.
Billing
The fees of archive data restoration depend on:
- Restoration speed
Most cloud service providers offer quick and standard restoration. Quick restoration is faster but more expensive, while standard restoration is slower but less expensive. RDA uses quick restoration by default. You can choose not to enable the automatic restoration function of RDA. But you will need to restore archive data manually using the restoration tools provided by the source cloud service provider before the migration.
- Validity period of restored objects
Cloud service providers charges users based on the validity period of restored data. In RDA, restored archive and deep archive objects are valid for three and five days respectively by default.
- Number of requests
Cloud service providers charges users based on the number of requests. If you enable archive data restoration when creating a migration task, RDA requests to restore each archive object before migrating it. When an archive object fails to be migrated and needs to be remigrated, RDA will request to restore the object again if it is not restored. But if the object is restored, RDA will migrate it directly.
For the detailed prices of cloud service providers, visit their websites.
Best Practices
RDA preferentially migrates restored archive objects during the migration to prevent migration failures due to the expiration of validity periods of these objects.
Since the network speed and the number of nodes are limited, restored archive objects may still fail to be migrated even when they are valid. You are advised to evaluate the network speed and the number of nodes before creating a migration task. You can create multiple tasks to ensure that restored archive objects can all be migrated before their validity period expires.
Restoring Archive Objects in Azure Blob Storage
Archive objects in Azure Blob Storage can be restored by either copying them to the online tier or changing their storage class to the online tier. RDA uses the second method by default. With this method:
- Archive objects will be restored to the hot tier and will be stored in this tier for a long time.
- Changing the storage class of objects in Azure Blob Storage does not affect their last modified time. If the tierToArchive policy is configured for these objects, add the daysAfterLastTierChangeGreaterThan condition. Otherwise, these objects may be moved back to archive tier after restoration.
- The hot tier in Microsoft Azure corresponds to the standard storage on the destination cloud. If you choose Reserve source storage type for the destination storage policy, archive objects from Microsoft Azure will be stored as standard objects after being migrated.