FAQ:Should I use a holdingdisk when the final destination of the backup is a virtual tape?: Difference between revisions

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(Created page with '{{FAQ Header}} Usually the answer is "yes"! Holding disks and vtapes serve a complete different purpose: holding disk allows different clients to backup simultaneously …')
 
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{{FAQ Header}}
{{FAQ Header}}
Usually the answer is "yes"!


[[Holding disk]]s and [[vtape]]s serve a complete different purpose:  holding disk allows different clients to backup simultaneously and the server collects the incomplete images in the holding disk.
[[Holding disk]]s and [[vtape]]s serve a complete different purpose:  holding disk allows different clients to backup simultaneously and the server collects the incomplete images in the holding disk.
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(e.g. when you want to burn the backups to a DVD later).
(e.g. when you want to burn the backups to a DVD later).


When you do not specify a holding disk, then only one [[DLE]] can be dumped at once. No parallelism is possible. And taper cannot use any of its algorithms either. This is true even when using vtapes.
* [[Holding disk]]s allow paralellism and [[vtape]]s do not allow it by default (It can be configured to do paralellism).
* [[Holding disk]]s and [[vtape]]s should never be on the same hard disk.
* Use [[Holding disk]]s if it is faster than the [[vtape]]s , eg. [[Holding disk]]s on SSD or [[vtape]]s on USB.
 
To get parallel dump to vtape, add the following in the storage section:
taper-parallel-write 10
  max-dle-by-volume 1


In the case where you have only one client (e.g. your home PC),
then avoiding a holding disk could indeed be a reasonable decision. 
But if your vtapes live on a slow USB-1 connected device, then a holding disk might
still be faster.
In case there are problems with your vtapes (e.g. the external disk with vtapes
In case there are problems with your vtapes (e.g. the external disk with vtapes
is full, or got disconnected), then Amanda can still fall back to degraded mode,  
is full, or got disconnected), then Amanda can still fall back to degraded mode,  
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= Credit =
= Credit =
Based on text by Stefan G. Weichinger, November - December, 2003, with updates in April, 2005.
Based on text by Stefan G. Weichinger, November - December, 2003, with updates in April, 2005.
Updates in January, 2018 by Jean-Louis Martineau
{{Languages}}
{{Languages}}

Latest revision as of 14:29, 29 January 2018

This article answers a FAQ (frequently asked question).

Holding disks and vtapes serve a complete different purpose: holding disk allows different clients to backup simultaneously and the server collects the incomplete images in the holding disk. When a backup image is complete, the server then adds it to the tape queue. The taper can choose the best file, depending on the criteria you set in "taperalgo". Especially "taperalgo largestfit" is helpful fitting as much as possible on a vtape. (e.g. when you want to burn the backups to a DVD later).

To get parallel dump to vtape, add the following in the storage section: 

taper-parallel-write 10
max-dle-by-volume 1

In case there are problems with your vtapes (e.g. the external disk with vtapes is full, or got disconnected), then Amanda can still fall back to degraded mode, and dump only incrementals to the holding disk.

Credit

Based on text by Stefan G. Weichinger, November - December, 2003, with updates in April, 2005. Updates in January, 2018 by Jean-Louis Martineau

Other languages: [[::FAQ:Should I use a holdingdisk when the final destination of the backup is a virtual tape?|English]] {{#ifexist: {{#if: | | {{#if: | :}}FAQ:Should I use a holdingdisk when the final destination of the backup is a virtual tape?}}/Fr |  • {{#if: |français| [[::FAQ:Should I use a holdingdisk when the final destination of the backup is a virtual tape?/Fr|français]]}}|}}

{{#ifexist: {{#if: | | {{#if: | :}}FAQ:Should I use a holdingdisk when the final destination of the backup is a virtual tape?}}/Zh-cn |  • {{#if: |中文（中国大陆）| [[::FAQ:Should I use a holdingdisk when the final destination of the backup is a virtual tape?/Zh-cn|中文（中国大陆）]]}}|}}


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