How low disk space is calculated?

Updated: 14 Dec 2011 | 4 comments

hgcs

0 0 Votes

This issue has been solved. See solution.

Hi!

I have a NAS (RAID5) device with a few backup-to-disk folders on it. The backup-to-disk folders are shared folders from the NAS. For every folder I can define the low disk space on its advanced property page. What does 0 value mean? What do a greater than 0 but different values for each folders mean?

Discussion Filed Under:

Backup and Recovery, Backup Exec - 2010, Backup Exec, Backing Up, Basics

Comments RSS Feed

Comments

Dec

2011

3 Votes +1

Striker 303

Symantec Employee

Backup Exec will use all available space

Backup Exec will use all available space on the drive and would

leave the amount of space you would select as "low space threshold"

In a windows system if you want to reserve 10 GB space for OS

and want BE to use rest, you would select 10 gb as ur low space threshold.

Dec

2011

3 Votes -1

VJware

Symantec Employee

Accredited

If 0Gb is specified, then BE

If 0Gb is specified, then BE never checks for a low disk space threshold & it does not reserve any amount of disk space...if you set other values such as 1Gb, it means, if BE would not submit new jobs for processing when this threshold is reached

EDIT*** http://www.symantec.com/docs/TECH55778

Dec

2011

1 Vote +1

RahulG

refer the following

refer the following document

http://www.symantec.com/business/support/index?page=content&id=TECH50329

Following lines from the document

It's important to distinguish the concept of a "disk space reserve" from the concept of "specifying how much space a B2D device can occupy". A disk space reserve tells Backup Exec how much "total free space" must be available on the volume where the B2D device resides at any give time. If the "total free space" of the volume falls below the prescribed "disk space reserve" threshold at any time for any reason, then job processing will be affected.

Example:

The D: volume has a 100 GB capacity.

There is a single B2D device located on D: with a disk space reserve of 30 GB.

If no other data resides on D: then the B2D device can grow up to 70 GB.

This can be illustrated with the following formula:

Capacity of 100 GB - disk space reserve of 30 GB = the maximum space the B2D device can occupy of 70 GB.

But if "other" data is copied to D: then the maximum space the B2D device can occupy is reduced by the size of the "other" data.

Example:

The D: volume has a 100 GB capacity.

There is a single B2D device located on D: with a disk space reserve of 30 GB.

The D: volume also contains a shared folder to which users can copy data which occupies 10 GB of disk space (this shared folder represents "other" data).

Now the B2D device can grow to only 60 GB.

This can be illustrated with the following formula:

Capacity of 100 GB - disk space reserve of 30 GB - shared folder of 10 GB = the maximum space the B2D device can occupy of 60 GB

So the disk space reserve tells Backup Exec how much free space must be available on the volume, not how much disk space the B2D device is allowed to occupy.

Each B2D folder has its own disk space reserve setting so if more than one B2D device resides on a volume it is necessary to account for the space occupied by the additional B2D devices. In such a scenario it is best to calculate the "maximum space the B2D device can occupy" of each B2D device independently and consider the additional B2D devices as part of "other" data. So as the additional B2D devices grow, the "other" data will grow and affect the "maximum space the B2D device can occupy" of all other B2D devices on the same volume.

Example:

The D: volume has a 100 GB capacity.

There are two B2D devices: B2D-Data and B2D-GRT

B2D-Data has a disk space reserve of 15 GB and has backup data occupying 20 GB of disk space.

B2D-GRT has a disk space reserve of 10 GB and has backup data occupying 25 GB of disk space.

The D: volume also contains a shared folder to which users can copy data which occupies 10 GB of disk space (this shared folder represents "other" data).

We must now calculate the size to which each B2D device can occupy independent of the other. We first start with B2D-Data and use the formula already established in the previous examples.

Capacity of 100GB - disk space reserve of 15 GB - shared folder of 10 GB - B2D-GRT of 25 GB = the maximum space that B2D-Data can occupy of 50 GB.

We now calculate the formula for B2D-GRT using the same formula.

Capacity of 100GB - disk space reserve of 10 GB - shared folder of 10 GB - B2D-Data of 20 GB = the maximum space that B2D-GRT can occupy of 60 GB.

From the examples above it can be seen that:

As "other" data grows the "maximum space a B2D device can occupy" shrinks.

As "other" B2D devices on the same volume grow the "maximum space a B2D device can occupy" shrinks.

If this response answers your concern, please mark it as a "solution"

Dec

2011

1 Vote +1

pkh

Trusted Advisor

Rahulg got it right, whereas

Rahulg got it right, whereas the other two previous answers are off the mark. If you have a couple of B2D folders on the disk and a couple of jobs are writing to these folders, you would not know which job will hit the low disk space threshold first.

You cannot set the low disk space threshold to either 0 GB or 0 MB. You need at least 1 GB or 1 MB. If you want to use the full disk, then don't enable the low disk space threshold. However, if you do not set a low disk space threshold and your disk is full, your job would just fail due to a lack of space. When you set a low disk space threshold and the threshold is reached, you would be prompted to free space on the disk so that the job can continue. If you managed to free enough disk space, then your job can complete. This is the advantage of setting the low disk space threshold. Also, if you are using a device pool for your B2D folders, you can enable the disk spanning option.

SOLUTION

How low disk space is calculated?

Comments

Backup Exec will use all available space

If 0Gb is specified, then BE

refer the following

Rahulg got it right, whereas

Would you like to reply?

Links

Technical Support

Symantec.com

Store

Community Stats