Re: [gentoo-user] Safeguarding strategies against SSD data loss

[Pandu Poluan <pandu@poluan.info>]

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On Oct 28, 2014 12:38 AM, "Rich Freeman" <rich0@gentoo.org> wrote:
>
> On Mon, Oct 27, 2014 at 1:23 PM, Volker Armin Hemmann
> <volkerarmin@googlemail.com> wrote:
> > Am 27.10.2014 um 16:36 schrieb Rich Freeman:
> >>  and a boot
> >> partition as I don't think grub supports it - it could be a bit of a
> >> PITA for a single-drive system.
> >
> > nope. But I don't see any reason to use zfs with a single drive either.
>
> True, not needing to use FUSE does simplify things, but I don't
> believe that grub supports zfs, so you would need a boot partition.
> Granted, a newer laptop would need that for EFI anyway.
>
> >
> >>  However, it is probably more mature
> >> than btrfs overall, and it certainly supports send.
> >
> > and if your send stream is corrupted, your data is gone. That is why I
> > prefer cp&tar to backup my zfs data tank.
> >
>
> If you ONLY save the send stream without checking it, then you're
> right that you're depending on its integrity.  I'd certainly be
> nervous about doing that with btrfs, probably less so with zfs but I
> can't really vouch for it.  I don't know what ability either
> filesystem gives you to verify a send stream in isolation.
>
> Now, what you could do is receive the send stream into a replica
> filesystem on the far end, and not consider the backup successful
> until this is done.  That would look like a btrfs-to-btrfs rsync
> operation, but it would be much more efficient in terms of IO.  It
> would require a daemon on the far end to run the receive operation and
> report back status, vs just dumping the files via scp, etc.
>
> Does anybody know if either btrfs or zfs send includes checksums?  I
> know the data is checksummed on disk, but I have no idea if it is
> protected in this way while serialized.
>

zfs has checksum for the send stream. That's why you can send the stream to
a file, and fail to import the file sometime later if something changes in
that file.

So, always do a filesystem replication. Don't just save the send stream.
Have the replica make the snapshots visible in poolroot/.zfs, and backup
the whole filesystem using a deduping backup system.

Rgds,
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