12-18-2012 08:51 PM
Hi guys,
Is there any way to check how much free space left in a tape?
I am using NB 7.5
Thanks,
Joseph
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12-18-2012 09:14 PM
hi
you can see the how much of data written using the below command, or from the GUI-> medias(under Kilobytes tab)
bpmedialist -m <mediaid> -U
so based on the media size that you use, you can caulcate the amount of free space left for future jobs..
lets say if you are using the LTO-5 tapes.. with capacity of 1.5 TB.
and bpmedialist is showing KBwritten as 700GB... so free space is 1.5 - 700 = 800GB.
Generally EMM server will take care all this behalf of us... :)
hope this helps.
12-18-2012 09:14 PM
hi
you can see the how much of data written using the below command, or from the GUI-> medias(under Kilobytes tab)
bpmedialist -m <mediaid> -U
so based on the media size that you use, you can caulcate the amount of free space left for future jobs..
lets say if you are using the LTO-5 tapes.. with capacity of 1.5 TB.
and bpmedialist is showing KBwritten as 700GB... so free space is 1.5 - 700 = 800GB.
Generally EMM server will take care all this behalf of us... :)
hope this helps.
12-18-2012 09:31 PM
Maximum tape capacity depends on tendency of data you when hardware compression is enabled because compression ratio of data affect amount of space required on tape. Some sort of data - especially already compressed ones like jpeg, mpeg or so - has low compression ratio, on the other hand, some sort of data like text file has high compression ratio.
So it is hard to estimate free space on tape exacty. But you can guess it by amount of data the tape which contains similar data become full with.
12-18-2012 09:40 PM
Thanks guys,
All your advice which I already aware of.
We are also using Networker which shows the function of the usage percentage of a tape.
I know it is not precise but looks goood. :)
12-18-2012 09:54 PM
There is NO WAY any backup application can know that.
An application that is displaying this, is merely guessing based on averages. How does any backup application know if you hcart tape is LTO1 or LTO4? And what kind of data you are backing up?
12-19-2012 12:31 AM
Just to show how difficult this could be to determine:
Using Nagallas example of bpmedialist -
# bpmedialist -m 300714 -U Server Host = server1 id rl images allocated last updated density kbytes restores vimages expiration last read <------- STATUS -------> -------------------------------------------------------------------------------- 300714 8 182 07/28/2012 06:00 07/28/2012 06:00 hcart3 1277324207 0 MPX 07/28/2013 06:00 N/A
So this media *still* has writeable capacity (there is no FULL status) & it has written 1277324207Kb (over 1Tb). Now the density is HCART3 - this could be *anything* as essentially it is just a label - however, I can confirm that this is an LTO3 which are advertised as 400/800 i.e. 400Gb native/800Gb compressed capacity.
So, how do I work out how much more I can write to this tape? The *closest* would probably be what Yasuhisa has stated:
guess it by amount of data the tape which contains similar data become full with.
12-19-2012 04:18 AM
I am not sure if i can write all this here, but proceeding...
It does show but it actually calculates against the native capacity of the tape. That is why you can see huge amount of data being written to tape between 100% - FULL. The thing here is you can define the capacity of the tape that is being used . If you say my LTO4 tape is of capacity 10TB, Networker starts dispalying 10% used after writng 1 TB of data to tape .
12-19-2012 04:55 AM
The overiding factor in all of this is that any 'calculation' will only be an estimate.
NBU has no understanding of tape capacity, and would in fact 'write' data quite happily to the same tape for ever.
What actually happens is that when the tape becomes full, this is detected by the firmware of the tape drive, and a 'flag' is set in the tape driver. The tape driver then informs NBU that the tape needs to be changed as it is full.
Martin