Chris Siebenmann wrote:
> | I very strongly disagree. The closest ZFS equivalent to ufsdump is
> | 'zfs send'. 'zfs send' like ufsdump has initmiate awareness of the
> | the actual on disk layout and is an integrated part of the filesystem
> | implementation.
>
> I must strongly disagree in turn, at least for Solaris 10. 'zfs send'
> suffers from three significant defects:
>
> - you cannot selectively restore files from a 'zfs send' archive;
> restoring is an all or nothing affair.
>
> - incrementals can only be generated relative to a snapshot, which
> means that doing incrementals may require you to use up significant
> amounts of disk space.
>
> - it is currently explicitly documented as not being forward or backwards
> compatible. (I understand that this is not really the case and that this
> change of heart will be officially documented at some point; I hope that
> people will forgive me for not basing a backup strategy on word of future
> changes.)
>
> The first issue alone makes 'zfs send' completely unsuitable for the
> purposes that we currently use ufsdump. I don't believe that we've lost
> a complete filesystem in years, but we restore accidentally deleted
> files all the time. (And snapshots are not the answer, as it is common
> that a user doesn't notice the problem until well after the fact.)
>
> ('zfs send' to live disks is not the answer, because we cannot afford
> the space, heat, power, disks, enclosures, and servers to spin as many
> disks as we have tape space, especially if we want the fault isolation
> that separate tapes give us. most especially if we have to build a
> second, physically separate machine room in another building to put the
> backups in.)
>
It does depend on your requirements. I use ZFS send/receive to save my
stuff
to (multiple) USB drives. One is stored onsite in a fire safe and the other
is stored offsite. There is no requirement that the target device is
spinning
except when you are copying. By using this method, I can follow the
declining price of disks over time: by the time I have 500 GBytes of
pictures,
a 1TByte disk will cost $70.
I have also sent snapshots to DVDs, but in truth tape will be easier because
it can store much more. Contrary to popular belief, tapes are still the
best
long-term storage medium. The commercial backup products work with
ZFS without needing to use the send/receive interfaces.
-- richard
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