# Backup an external driver that is not always connected

**URL:** https://forum.duplicati.com/t/backup-an-external-driver-that-is-not-always-connected/14083
**Category:** Support
**Created:** [March 13, 2022, 7:49am UTC](https://forum.duplicati.com/t/backup-an-external-driver-that-is-not-always-connected/14083 "2022-03-13T07:49:24Z")
**Posts on this page:** 1
**Showing post:** 2

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### Author: ![drwtsn32](https://forum.duplicati.com/user_avatar/forum.duplicati.com/drwtsn32/32/2591_2.png) [@drwtsn32](https://forum.duplicati.com/u/drwtsn32)
#### Post date: [March 14, 2022, 3:53am UTC](https://forum.duplicati.com/t/backup-an-external-driver-that-is-not-always-connected/14083/2 "2022-03-14T03:53:37Z")

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There’s a lot to unpack here, and many of these are interdependent.

> [@AnnyClair](#):
>
> The first problem is, this HD is not always connected

I think you have a couple options here. If the external HD was in its own backup job, you could use run-script-before to decide if the backup should run or not. (It could test for the presence of the external hard drive.)

But in question 2 you say that you also want files on C: in the same backup. Must it be in the same backup?

> [@AnnyClair](#):
>
> … Duplicati considers that the files have been deleted, and deletes the files on S3.

This depends on your retention policy. What do you intend to use?

> [@AnnyClair](#):
>
> If at some point I manually remove folders from the backup folder list, will they be deleted from S3?

They will be if dictated by your retention policy. Also, you can use the [PURGE](https://duplicati.readthedocs.io/en/latest/04-using-duplicati-from-the-command-line/#the-purge-command) command to delete files from the backup data.

> [@AnnyClair](#):
>
> I currently have 1TB of files (but it can go up to 2TB)

Then I would recommend setting `--block-size` to 1 or 2MB. This is the deduplication block size and must be set before the first backup is performed – it cannot be changed later. (See [Choosing sizes in Duplicati](https://duplicati.readthedocs.io/en/latest/appendix-c-choosing-sizes-in-duplicati/) for more info.)

> [@AnnyClair](#):
>
> I intend to create a Rule in S3 to move the files to Glacier

Archive-class storage with most providers can cause issues with Duplicati. If you insist on using it, you probably need to set a couple options as mentioned in [this post](https://forum.duplicati.com/t/amazon-glacier-best-practices/13330/6). Also you probably should use unlimited retention.

If you use unlimited retention, then your earlier concerns may be irrelevant (except the PURGE-ing of data).

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