Re: big dump compare to tape size

2004-03-26 Thread Eric Siegerman
On Fri, Mar 26, 2004 at 04:04:05PM +0100, BRINER Cedric wrote:
 the tapes are 70Gb

Is that 70 GB native, or with hardware compression taken into
account?  (If the latter, it can only be approximate; depends how
compressible the data is.)

Do you in fact have hardware compression enabled?  (See the list
archives for discussions as to (a) why that's usually considered
a bad thing, and (b) the difficulty in turning it off and making
it *stay* turned off when reusing tapes that were initially
written with it turned on.)

 and some dumps are about 30Gb
 
 +   These dumps were to tape WeeklySet076. 
 +   *** A TAPE ERROR OCCURRED: [[writing file: short write]].
 
 so the tape have for example 45Gb already on it, when it tries to flush the 30Gb. So 
 I end up that:
  the 30Gb is not flushed
  the others dumps (40 dumps of 1Gb) are not dump to the tape. When a lot of them 
 could be dumped
  
 So:
 -is amanda able to maximise the amount on data that it stores or does it only flush 
 without any algorithm. 
 -or my config file which is uncorrect
 -or Is there a way to breaks into smaller pieces the big dumps 
 
 my config file for the tape configuration
 
 define tapetype DLT4000 {
 length 4 mbytes # 40 Gig tapes
 filemark 8 kbytes   # 16 also works, 32 doesn't
 speed 1536 kbytes   # 6 Mb/s accd to Compaq   ??? see bellow def of DLT
 }
 
 thanks in advance
 
 Cédric Briner
 
--

|  | /\
|-_|/ Eric Siegerman, Toronto, Ont.[EMAIL PROTECTED]
|  |  /
It must be said that they would have sounded better if the singer
wouldn't throw his fellow band members to the ground and toss the
drum kit around during songs.
- Patrick Lenneau


Re: big dump compare to tape size

2004-03-26 Thread Eric Siegerman
[sorry about that half-a-reply, folks; clumsy fingers...]

On Fri, Mar 26, 2004 at 04:04:05PM +0100, BRINER Cedric wrote:
 +   These dumps were to tape WeeklySet076. 
 +   *** A TAPE ERROR OCCURRED: [[writing file: short write]].
 
 so the tape have for example 45Gb already on it, when it tries to flush the 30Gb. So 
 I end up that:
  the 30Gb is not flushed
  the others dumps (40 dumps of 1Gb) are not dump to the tape. When a lot of them 
 could be dumped
  
 So:
 -is amanda able to maximise the amount on data that it stores or does it only flush 
 without any algorithm. 

There are a number of algorithms it can use.  See the description
of taperalgo in amanda(8).

 -or Is there a way to breaks into smaller pieces the big dumps 

It's not yet possible to split a single DLE across multiple
tapes.  John Stange (and others?) are working on it (hooray!), so
stay tuned.

You can, however, split one DLE into a number of smaller DLEs, by
using gnutar instead of dump, and using exclude and include
directives for each one.  There are a couple of disadvantages to
this:
  - if your clients have non-standard metadata, gnutar might not
be able to back it up
  - the file-access times get munged by your backup procedure
  - gnutar can be slower at some things than dump is, especially
at getting estimates
These (especially the second), plus lack of pressing need, are
enough to keep me from using this approach myself, but a lot of
people here swear by it.

 the tapes are 70Gb
 [...]
 my config file for the tape configuration
 
 define tapetype DLT4000 {
 length 4 mbytes # 40 Gig tapes
 filemark 8 kbytes   # 16 also works, 32 doesn't
 speed 1536 kbytes   # 6 Mb/s accd to Compaq   ??? see bellow def of DLT
 }

I've never worked with DLT drives, but judging by the specs, I
think there's some confusion here.
http://www.quantum.com/am/products/dlt/dlt4000/specifications.htm
says that DLT 4000 is 20 GB native, and 40 GB (estimated) with
hardware compression taken into account.  So if you in fact have
a DLT 4000, I don't think the 70 GB is realistic at all, and
even 40 GB is a bit dubious.

--

|  | /\
|-_|/ Eric Siegerman, Toronto, Ont.[EMAIL PROTECTED]
|  |  /
It must be said that they would have sounded better if the singer
wouldn't throw his fellow band members to the ground and toss the
drum kit around during songs.
- Patrick Lenneau