Migration Data Volume Calculator
Find out how much data you really transfer once daily change, waves, validation and retries are counted.
Each one fills in the fields below for a typical workload of that kind. You can change any of them.
Your link
Extra copies
- Into the cloud
- 513 TB
- Back to the data center
- 32 TB
- Added to the dataset
- +14%
- Sync keeps up
- Yes
To land 450 TB.
Into the cloud
| First copy3 waves of 150 TB, over the network | 450 TB |
| Changes during the first copyData that changes after it was copied is sent again; on average half of each wave is already across | 32 TB |
| Sync before each cutover0.50% a day of each wave, for 7 days | 16 TB |
| Validation copies0% of the data copied a second time | 0 TB |
| Resent after failures3% of what crosses the network | 15 TB |
| Total | 513 TB |
Back to the data center
| Reverse sync for rollbackChanges made in the cloud, sent back for 14 days after cutover, with resends | 32 TB |
| Total | 32 TB |
Can the sync keep up?
What this means
- Change and retries add 14%
You move 513 TB to land 450 TB. A plan that sizes the network or the transfer service fee from the dataset alone is short by that much.
- Rollback traffic is billed egress
32 TB flows back to the data center after cutover. Ingress is free on every cloud; this direction is not. Price it in the egress calculator.
What this model assumes
Show
- Waves are equal and go one after another. Each wave is copied, kept in sync for the days above, then cut over; waves already cut over stop changing on the source.
- Change during the first copy is halved. Data that changes before it is copied goes across in its new state; only change to data already sent is sent again, and on average half of a wave is across while it copies.
- The change rate is new data a day. Rewriting the same block twice in one day counts once; every day’s changes are sent.
- The link figure includes 92% protocol efficiency, the same default as the transfer time calculator.
- Retries cost time even when they are not billed. Google’s Storage Transfer Service does not bill failed attempts; the bytes still cross the link again.
Planning the target architecture?
Cloud Cost Audit: We review placement, network design and egress before the first bill arrives, so the migration does not carry avoidable transfer costs into the cloud. From $1,500, fixed. Nothing paid upfront.
Questions
Why do I transfer more data than I have?
Because the data keeps changing while you copy it. Changes to data already sent are sent again, every wave is synchronized until it cuts over, some data is copied twice to validate it, and failed transfers are resent. On a busy system that can add a fifth or more to the dataset.
What happens if the data changes faster than the link can copy it?
Incremental sync never catches up, so the cutover never comes. The page checks the daily change in the wave being moved against what the link moves a day. The fixes are more waves, more bandwidth, or a first copy on an appliance with a short, planned write freeze.
How long will the cutover window be?
As long as the last sync takes: the changes since the previous sync, at the link's rate. A 150 TB wave changing 0.5% a day, synced daily over 1 Gbps at 70%, needs about two and a half hours of frozen writes. More frequent syncs or smaller waves shorten it.
Is sending data back to the data center free?
No. Ingress into AWS, Google Cloud and Azure is free, but data leaving the cloud is billed egress. Reverse sync for a rollback plan, and any hybrid traffic after it, is charged every month at internet or private connection rates. Price it in the egress calculator.
What daily change rate should I use?
Measure it: the daily size of incremental backups is the best figure most teams already have. As a starting point, file shares often change under 0.5% a day and transactional databases can pass 2%. Snapshot deltas from the storage array are another good source.
Related tools
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OpenCloud Egress Cost Calculator
The move is one bill. Your new architecture's traffic is every month's bill.
OpenMore tools for: Network and data transfer
The migration ends. The traffic pattern stays.
Once you are in the cloud, Finitizer shows which workloads send data across zones, regions and back to your data center, and what each path costs a month.
See how Finitizer works