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USB External Dirve Incremental Backkup Much Slower than Full Backup

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I have an external drive (WD Easystore 5TB) connected via USB 3.0. When ACPHO does a full backup to that drive, the transfer rate is reported at 200-300 Mb/s. However, when ACPHO does an incremental backup to that drive, the reported transfer rate is 3-10Mb/s. Why the big difference? Is it due to the read-write and other processing it takes to make an incremental backup, or what?

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Is it due to the read-write and other processing it takes to make an incremental backup, or what?

Doing an initial backup is relatively simple but still involves Acronis doing things to both the source and target drives. With incremental backup it has to identify the segments (disk + partitions) or bits (files and folders) that are different, and then copy them; this may mean that Acronis has to check not only the original backup but subsequent incremental backups. If the backup is encrypted (as is recommended) then there will be overhead for the encryption. The data transfer rate is decreased because data is being processed more extensively with incremental backups.

Ian

Thanks. That is what I thought, but I didn't think it would be such a big difference. I would conclude that also explains why backups to the cloud, being incremental, are only done at about 25% of the available upload speed.

Yes, it explains the speed of Cloud backups. I find the speed highly variable; the best I can recall getting was 26Mbps on a 100/40 Mbps cable connection; but that was extraordinary. I am now on a 100/20 connection which is not so flash, but in practice makes no difference to cloud backup times. I think server load balancing is also a factor in the relatively low backup rate.

Ian

My cable ISP rate is 200/10, with SpeedTest measured upload speeds often at 11Mbps, but the overall Cloud backup speed is reported by Acronis in the 2Mbps range. During the actual Cloud backup, Task Manager will show uploads of up to 4Mbps, but the overall lower average is obviously due the overhead factors. That means that if my ISP should offer a faster upload speed plan, it probably wouldn't affect my Cloud backups much.

Thanks for the input, Ian. I have marked the thread as solved.