You want to migrate an on-premises 100 TB Microsoft SQL Server database to Google Cloud over a 1 Gbps network link. You have 48 hours allowed downtime to migrate this database. What should you do? (Choose two.)
A.
Use a change data capture (CDC) migration strategy.
B.
Move the physical database servers from on-premises to Google Cloud.
C.
Keep the network bandwidth at 1 Gbps, and then perform an offline data migration.
D.
Increase the network bandwidth to 2 Gbps, and then perform an offline data migration.
E.
Increase the network bandwidth to 10 Gbps, and then perform an offline data migration.
AUse a change data capture ***** (CDC) migration strategy.
BMove the physical database servers from on-premises to Google Cloud.
CKeep the network bandwidth at 1 Gbps, and then perform an offline data migration.
1 Gbps = 1*24*60*60/8 = 10,800 GB = 10 TB per 24 hrs So, 20 TB per 48 hrs
DIncrease the network bandwidth to 2 Gbps, and then perform an offline data migration.
So, 40 TB per 48 hrs
EIncrease the network bandwidth to 10 ***** Gbps, and then perform an offline data migration.
So, 200 TB per 48 hrs
Answer: A E
A, C
The question doesn't tell you that you have to move the database within 48 hours from right now - it says you're allow 48 hours of downtime. i.e. You can schedule it. C, D, and E all require an offline transfer, so increasing bandwidth wouldn't help. 1 Gbps should be enough to handle CDC updates within 48 hours after the initial offline transfer is complete, and it minimizes cost.
C. As per data transfer documentation, 1G should be sufficient to transfer 10TB in 30 hours (required is 48 hours) https://cloud.google.com/architecture/migration-to-google-cloud-transferring-your-large-datasets#online_versus_offline_transfer
No need to upgrade bandwidth.
Option A & E is correct:
The questions and the option tell us two scenarios:
First Scenario: Option A: CDC
Setup CDC and replication. Within 48 hours this can be completed using 1 GB network bandwidth. Database is required restart to change configuration and the rest is online during replication
Second scenario: offline migration (offline database migration)
Database need to be shutdown and take a full backup and transfer it to GCP.
At this points we can eliminate option C and D because option C transfer 100 TB over 1 GB network bandwidth required 12 days (above allowed downtime 48 hours) and option D transfer 100 TB over network bandwidth 4,74 days (113,78 hours) which is above allowed downtime 48 hours
A, E.
According to Google’s data transfer chart, 100 TB across a 1 Gbps link would take 12 days. I don’t think you can physically move your own equipment into a Google DC. Eliminate B. Increasing the bandwidth to 2 Gbps and doing an offline migration anyway wouldn’t help. The Google Transfer Appliance comes in 7 TB, 40 TB and 300 TB sizes. However, the turnaround time (Google ships the appliance to you, you load it with data, you ship it back, Google unloads it to a Cloud Storage bucket) is approximately 3 weeks. Eliminate C and D. That leaves A and E. A 10 Gbps link would transfer 100 TB in 30 hours. That leaves 18 hours for a CDC solution to sync the data.
https://cloud.google.com/architecture/migration-to-google-cloud-transferring-your-large-datasets#online_versus_offline_transfer
Ideally, you can transfer 1 GB in eight seconds over a 1 Gbps network.
https://cloud.google.com/architecture/migration-to-google-cloud-transferring-your-large-datasets
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