Re: Dump Vs Tar tradeoffs (if any)

2003-12-23 Thread Andrew Hall 
George,

It's not the only reason I'm sure, but if you wish to exclude files from
your archive you must use tar.  Dump does not allow this. 

Drew

On Tue, 2003-12-23 at 11:42, Henson, George Mr JMLFDC wrote:
 All,
 
 We are still new to Amanda and would greatly appreciate some advise on
 how to best configure  the system
 
 What are the advantages or disadvantages to using tar instead of dump?
 Is there a difference in restoring a single file? a file system? or
 the whole system? (other then changing restore to tar x)
 
 If it helps, we are using HP/UX 11i (on an N class system) to backup
 about 10 client (HP/UX 11, HP/UX 11i, and Linux) onto LTO media using
 a C7200 silo/changer.
 
 Thank you,
 George Henson

RE: Dump Vs Tar tradeoffs (if any)

2003-12-23 Thread Mark_Conty 
Yes, one of the big differences is that 'tar' lets you break up larger 
filesystems into smaller, more manageable DLEs, as well as excluding 
specific files or file patterns.

Be sure that you use 'tar' version 1.13.25 -- nothing older, and nothing 
newer, until you hear that someone has certified it to be compatible 
with Amanda.  (The latest version, 1.13.92, causes indexing not to 
work.)

Also, I've found that 'tar' seems to take longer in the estimate phase 
than do 'dump' (and 'vxdump'), but for all I know, that could be due to 
local influences (e.g., disk traffic).  Or has anyone else also found it 
to be the case that 'tar' estimates take longer than those from 'dump'?

-- Mark

RE: Dump Vs Tar tradeoffs (if any)

2003-12-23 Thread Mitch Collinsworth 

On Tue, 23 Dec 2003 [EMAIL PROTECTED] wrote:

 Also, I've found that 'tar' seems to take longer in the estimate phase
 than do 'dump' (and 'vxdump'), but for all I know, that could be due to
 local influences (e.g., disk traffic).  Or has anyone else also found it
 to be the case that 'tar' estimates take longer than those from 'dump'?

Tar has to stat every file to find out how much is going to be backed
up.  Dump just has to look at the filesystem as a whole.  Far less
work involved.

-Mitch

Re: Dump Vs Tar tradeoffs (if any)

2003-12-23 Thread Eric Siegerman 
On Tue, Dec 23, 2003 at 11:42:14AM -0500, Henson, George Mr JMLFDC wrote:
 What are the advantages or disadvantages to using tar instead
 of dump?

(This is partially brief repetition, but also contains new
points.)

In dump's favour:
  - The estimate phase is faster

  - It doesn't change any of the timestamps of files it's backing
up (tar doesn't change mtime either of course, but can't
avoid changing either atime or ctime (actually, I recently
read that Solaris provides a way, if you're root, but I don't
know whether GNU tar takes advantage of it)

  - You can do interactive restores natively.  (amrecover gives
you the same functionality, regardless of dump vs. tar, so
this difference *only* applies if Amanda isn't in the loop at
restore time, or if you don't have the index files, which
amrecover requires.)

  - Dump programs are customized to the local file system's
idiosyncracies.  I'm guessing (but don't know) that this
means that dump can back up system-dependent metadata that
tar has no clue about (ACLs, Linux ext2 chattr flags,
FreeBSD's chflags variant thereof, and the like)

In tar's favour:
  - You can exclude files

  - You can split a partition into multiple DLE's.  This is
necessary if you have partitions larger than will fit on a
single tape, since Amanda can't split a single dump onto
multiple tapes (not yet anyway; work is in progress,
hooray!).

  - Dump is reported to be undependable on Linux -- Linus says
so, anyway.  (He has a thing against dump, so doesn't see
that as a problem, but IMO it's because Linux has deviated
from standard UNIX in undesirable ways.  Regardless of blame,
though, it's an issue to be dealt with.)

  - Backups are portable.  The downside of every dump being
customized to its file system is that you very likely can't
restore a dump from platform X using platform Y's restore.
I've never tried cross-file-system restores on the same box
(restoring from a Solaris VXFS dump onto a Solaris ufs
partition, for example), but I imagine that whether you can
get away with it depends on the specific combination and the
specific platform.

--

|  | /\
|-_|/ Eric Siegerman, Toronto, Ont.[EMAIL PROTECTED]
|  |  /
It must be said that they would have sounded better if the singer
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- Patrick Lenneau