Choice of file system for external backup hard disk

[janpeter1]

Hi,

I have used my ReayNAS 314 for a few years and run the latest OS on it. Regularly I make backup on an external HD of the important part of what is stored on the NAS. I have two external backup HD and swithc between the two. The first one is with EXT3 file system and for the second one I use BTRFS.  One of the HD are alway at anontjher location. So I follow the school book.

I consider now to make the full backup from scratch on the EXT3 disk and I consider to swith to BTRFS here too. I am just curious what you would recommend. Is BTRFS "stable" enough to use for both my backup? Other reasons to actually continue with EXT3?

Also when I make a full backup we are talking about 3 GB and that will take some time. Is it good too divde the backup in parts so that the NAS can "rest" for some time or it is just to run it all. I suspect it will take more than 24 hours. The hard disk I use are Wester Digital and bought a few years back and was on the compliance list for the NAS when I bought it. I hope they still are. 

Appreciate some input here. Thanks / Jan Peter

[StephenB]

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@janpeter1 wrote:

I consider now to make the full backup from scratch on the EXT3 disk and I consider to swith to BTRFS here too. I am just curious what you would recommend. Is BTRFS "stable" enough to use for both my backup? Other reasons to actually continue with EXT3?

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I think it's stable enough (and if it weren't then you shouldn't use it for either backup).  The main thing is that you want to be able to access the files using something other than the NAS.  If you have a linux PC, then you should install btrfs, and make sure you can read both back up drives.  If you don't have a linux PC, then you should be using NTFS.

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@janpeter1 wrote:

Is it good too divde the backup in parts so that the NAS can "rest" for some time or it is just to run it all. 

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I think it's fine to just run it all.  Also, if you are making incremental backups, then it's a good idea to occasionally make a full one (just to make sure there are no underlying disk errors).

[Hopchen]

I use BTRFS on my USB devices. I like that because I can snapshot by data on the USBs. It is fantastic for backup versioning, for example.

[StephenB]

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@Hopchen wrote:

I use BTRFS on my USB devices. I like that because I can snapshot by data on the USBs. It is fantastic for backup versioning, for example.

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I assume you are doing that yourself (from ssh), since the built-in backup jobs don't have that facility.  Is that correct?

[Hopchen]

Yup that is correct. I wish that was a feature in the NAS admin panel. I have a cronjob that does this for me 🙂

[janpeter1]

Thanks for the comments but I like to sharpen my questions.

The reason for me to make both external HD to be BTRFS is that I "imagine" that since the NAS is on BTRFS then if backup is also on BTRFS then I get a slightly higher degree of safety of data integrity, compared to having the external HD as EXT3 (or EXT4)

The drawback is you put all eggs in the same basket, so to speak. But I guess by now BTRFS on ReadyNAS has matured and I have had no problems these years I have used it. But I have not tested it much though.  

So is here a gain in data integrity by having the external HD in BTRFS, however small? Or there is too many other sources of corruption anyway so it does not matter. After all I have an ordinary NAS and not the one with special RAM-memory to protext agains data corruption there. 

What do you think?

[StephenB]

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@janpeter1 wrote:

So is here a gain in data integrity by having the external HD in BTRFS, however small? Or there is too many other sources of corruption anyway so it does not matter.

The only gain I see is that if BTRFS checksums are enabled on the external hard drive, then you could detect that files stored on the drive became corrupted later on.  I'm not convinced that happens often enough to worry about - it's certainly not something I've ever seen on my own NAS.

[janpeter1]

I understand that bit-corruption etc is a small effect and my stuff is not that incredible valueable. But since I now have the tehcnology here, why not use it?

So how do I turn on checksums on my external Western Digital external disk?

Must be some setting when I format the disk from the NAS right?

Or is this technology only possible if the backup is made by another Netgear NAS?

[StephenB]

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@janpeter1 wrote:

So how do I turn on checksums on my external Western Digital external disk?

Must be some setting when I format the disk from the NAS right?

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Actually it's an option when the file system is mounted.  I don't know how the NAS normally mounts btrfs volumes on external drives - you would sort this out with ssh, and if necessary remount the hard drive to enable COW and DATASUM.

[Hopchen]

Hey both

Here is the default mount when using BTRFS USB in the NAS.

/dev/sdc1 on /media/USB_HDD_1 type btrfs (rw,noatime,nodiratime,nospace_cache,commit=604800,subvolid=5,subvol=/)

It mounts with both CoW and Checksumming enabled by default 🙂

[StephenB]

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@Hopchen wrote:

Here is the default mount when using BTRFS USB in the NAS.

/dev/sdc1 on /media/USB_HDD_1 type btrfs (rw,noatime,nodiratime,nospace_cache,commit=604800,subvolid=5,subvol=/)

It mounts with both CoW and Checksumming enabled by default 🙂

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Great, thx for looking into that.