Exam Professional Cloud Database Engineer topic 1 question 87 discussion

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, 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

At 1 Gbps, transferring 100 TB of data could take much longer than 48 hours, so this is not a viable option.

A and C

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.

1 minutes = 60 seconds 1 hour = 60 minutes = 60 * 60 = 3_600 seconds 1 day = 24 hours = 24 * 3_600 = 86_400 seconds 48 hours = 2 days = 86_400 * 2 = 172_800 seconds Network link 1 Gbps, 48 hours transfer 172_800 Gb = 172_800/8 GB = 21_600 GB < 100 TB Network link 2 Gbps, 48 hours transfer 43_200 GB < 100 TB Network link 10 Gbps, 48 hours transfer 210_600 GB = 205.66 TB > 100 TB.

I think the question tricks you into thinking that you need more bandwidth. For offline, you don't need bandwidth. So answers is A and C.

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 and C for me

Correct answer is A & D.

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.

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

I confirm pk349 calculations