Create and store a snapshot on a USB drive procedure

[waves]

I got my freenas running about a month ago and got my data transferred to it from an openmedia vault using rsync. I have parts to build a 2nd freenas server as well.

I have 2 drives (8TB each) which I would like to save snapshots to periodically. They will be rotated offsite. My question is regarding exactly how to setup the usb drive and store snapshots on it.

I read usb isn't ideal for backing up over but it's what I have available currently. I plan to scrub both drives when I rotate each back onsite to verify the historical snapshots on them are still trustworthy. The usb ports on my freenas are usb 3.0 from a pcie card. The freenas contains a single pool which has 8TB of useable space. I'm currently using about 1.5TB.

I have wiped the usb drive by plugging it into the freenas and wiping it using the GUI and the disks tab. Shall I then follow the steps shown here in order to make a pool on the usb drive?

9. Storage — FreeNAS®11.2-U3 User Guide Table of Contents

www.ixsystems.com

Choosing these options:
Single vdev
Striped

Once the vdev is created I am a bit unsure of how I should setup snapshots. I would like to preserve space on the freenas for new data, if that is possible. So I'd rather not have to keep every snapshot that I am interested in preserving on the freenas. From what I read it sounds like you must take a snapshot and at least temporarily store it on the freenas before then replicating it to the usb drive then maybe you can delete the snapshot on the freenas?

I found snippets of old guides regarding how to take a snapshot and other guides for how to do replication (all the examples were remote destinations not usb and didn't explain the GUI options) but none that were recent for 11.2 of 11.3 (I updated the OS to 11.3. Didn't update the pool because I don't have a backup of the dataset currently).

I think a rough outline of what needs to happen after the usb drive has a pool on it would help me a lot. Then I'd maybe be able to understand what sections for the freenas manual I should be following. As it is now, I'm unsure of basic things like the question in italics above. Thanks!

 

[waves]

I believe I got the USB drive setup correctly. I realized the striping or raidz# options were not something the GUI wound up asking you to make a selection about probably because it was only a single disk. The guide I was following was old. I now have a pool on the usb drive called usb_backup_1.

I also setup a periodic snapshot task of the pool (media-storage) I want to backup. The status of it seems to be staying as "pending". I have the begin and end times of the snapshot set as the defaults which is 00:00 to 24:59. Does freenas run tasks every few hours? I need that periodic snapshot task to run because I noticed if I try to now setup the replication task, it says there are no snapshots of media-storage and that a snapshot will be created. I already made a snapshot tasks (the one that is stuck pending) so I don't want to setup the replication task and have it create snapshots if my periodic task is already set to run.

Is there a rule of thumb for how long to set the snapshot lifetime for? The data in this pool is all historical and doesn't change much. Small additions are made from changing word doc files or new photo uploads occasionally. I saw the default was 2 weeks. I made it 3 weeks. Will I need to manually delete snapshots from the usb drive eventually to avoid it filling up? The freenas sounds like it will take care of old snapshots by deleting them due to that 3 week lifetime limit.

 

[JaimieV]

The "Snapshot retention policy" in your replication definition will allow you to set the job to harvest old snapshots same as the source pool, or to have a custom one. If the data delta is small, no reason not to set it to longer on the USB.

There's no rule of thumb, it's how long *you* want to keep the snapshots for *your* potential recover purposes. Generally more is better for an archive destination which this basically is. If you expect to sometime have to recover a deletion made a few weeks ago, set it to long enough to do that. You can worry about hitting the 8TB HDD limit when you get there.

 

[waves]

Is it possible to scrub the external usb drive and correct errors if any are found, perhaps from bitrot? I see the option on the external drive's pool so it would seem like you could do it but it has no redundancy since it is a single drive. It would seem to me, that you would not be able to repair any incorrect bits since there are no other copies to compare them to.

The main freenas is replicating to a 2nd onsite freenas along with this external drive. The external drive is being taken offsite after replications for safe keeping. I was wondering if doing scrubs on the usb drive is useful.

 

[waves]

Additionally when ejecting my external drive it asks if I want to: "Delete Configuration of shares that used this pool?" By shares does it mean network shares? I don't have any network shares with that external drive. Or is it referencing the pool setup on that drive? I'd like to be able to plug the drive back in later so I can have the replication tasks replicate new snapshots to.

 

[subhuman]

I read usb isn't ideal for backing up over but it's what I have available currently. I plan to scrub both drives when I rotate each back onsite to verify the historical snapshots on them are still trustworthy.

Is it possible to scrub the external usb drive and correct errors if any are found, perhaps from bitrot?

Both of the above are very dependent on the USB-to-SATA adapter properly passing SMART data. Some do; most don't.
You may get lucky and have a "proper" device, but you also may have one that isn't correctly passing SMART data and instead is only giving you a false sense of safety.

 

[waves]

Both of the above are very dependent on the USB-to-SATA adapter properly passing SMART data. Some do; most don't.
You may get lucky and have a "proper" device, but you also may have one that isn't correctly passing SMART data and instead is only giving you a false sense of safety.

I do have a 2nd freenas running now and the 1st freenas is replicating snapshots to it. The usb backup is for offsite backup. I don't have another location with internet that I can keep the 2nd freenas at. The SMART data appears to be passing correctly. I can see all the same data that the 2 internal SATA drives are passing. There are also 4 SAS drives inside too. I had another adapter which didn't show the same amount of SMART data as the internal drives.