[BUGS] Remote backups, imap too

[Peter Jeremy]

Hi Jerahmy,

On Sat, Dec 08, 2007 at 05:29:02AM +1100, Jerahmy Pocott wrote:
>Just looking for some options/suggestions on remote backup tools,
>I was thinking of using rsync, but then I was thinking maybe it's not
>really good for backups?

I'd say the first thing you need to decide on is what you want from
your backups.  When I think "backup", I think of keeping a mixture of
full and incremental backups (probably multiple copies from different
dates) so that I can recover accidently lost/corrupted files from some
time in the past as well as recovering from a dead HDD.  OTOH, rsync
is intended to replicate a directory tree so you have a second copy of
your directory tree at some point in time.

Issues that you might want to consider when choosing between different
tools include:
- How many backups do you want to keep?
  It's easier to manage individual files than complete directory trees.
- Do you need to compress backups to reduce storage requirements?
  If yes, then directory trees are probably unsuitable.
- Do you use any fancy metadata options (ACLs, chflags etc)?
  These may not be replicated using rsync.
- Do you need to accurately reproduce sparse files?
  Only dump(8) can do this, though tar/cpio/rsync can handle sparse files,
- Do you need to access your backups as a filesystem?
  If yes, then rsync is the better option
- Do your backups need to be accessible/restorable from a different OS?
  If yes, then dump(8) is probably not a good option.
- What security issues do you need to consider for both storage of the
  backups and transfer of data between the host and backup server?
  You may need to consider encryption.

>but then if the source file has been removed I may not want the remote
>file to also be removed..

You can't easily express "may not want" with rsync - you have a choice
of either deleting or keeping removed files.  With tar/cpio/dump, you
decide when you restore.

>have some of these 'lacie ethernet disk mini' things, they support
>smb, afp, ftp, bonjour. I had considered using samba to mount them

Of these, FreeBSD can only natively support SMB or FTP, though you can
probably find an AFP client in ports.  I'm not sure about the other
*BSD. I've successfully used smbfs (see mount_smbfs) at work, though
only to read files from a SMB server.  AFAIK, SAMBA does not include a
filesystem client, only an FTP-like client.

Note that SMB was designed for use over a LAN and I'm not sure how
well it behaves across a WAN.

> The file permissions might be an issue?

SMB file permissions don't map cleanly onto Unix file permissions so
this may be an issue depending on your requirements (though LaCie are
using Linux ext2 or ext3 as the underlying FS).

>You can also download the source for these drives os, it looks
>to be based on a linux kernel. I suppose it might be possible to
>build a version with rsync in it..

Almost all of these SOHO SAN/NAS boxes are based on embedded Linux.
Keep in mind that the embedded CPU is probably not x86 - it's more
likely to be PPC or ARM.  And replacing the firmware would void any
warranty.

My personal approach would be to use compressed dumps - either via SMB
or by hacking tool to stream over FTP.  You may come to different
decision based on your requirements.

>And totally unrelated to this, anyone care to recommend an imap
>mail server for bsd? I'v only ever used sendmail..

Sorry, no.  Though one data point here is how much traffic will the
mail server be handling?  Something to manage your personal mail has a
different set of trade-offs to something that a major ISP might need.

-- 
Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.
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