Discussions specific to tape backups
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jfnk1ng
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LTO8 Capacity

Post by jfnk1ng » Mar 14, 2018 12:17 pm

Hi

Just installed an LTO-8 drive and starting the process of inventorying and cataloguing tapes. I notice the tape capacity is shown as 10.4TB, as compared to the quoted LTO-8 raw capacity of 12.8TB. Is this expected, or is there something I can do within Veeam to increase the available capacity?

Thanks

DGrinev
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Re: LTO8 Capacity

Post by DGrinev » Mar 14, 2018 1:02 pm

Hi Jeremy,

Can you check what capacity is shown in the tape library interface?
I am almost sure that Veeam B&R shows you the value from the library and there is nothing we can do to increase the capacity. Thanks!

v.Eremin
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Re: LTO8 Capacity

Post by v.Eremin » Mar 16, 2018 6:04 pm

Indeed, while estimating tape free space, backup server relies on information provided by drive or library.

So, if free space value is not reflected correctly, then, it might be worth checking tape device firmware, patches, etc.

Thanks.

jfnk1ng
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Re: LTO8 Capacity

Post by jfnk1ng » Mar 19, 2018 10:52 am

Thanks Dmitry and Vladimir

I have had a look at the vendor-provided dashboard on the server and it reports that the inserted tape has the full 12TB capacity. This still points to your suggested cause of either the info that the server is passing to Veeam, or perhaps how Veeam is interpreting that info. LTO-8 is still pretty new (the Quantum drive we are using was the first we could find that was commercially available) so I can understand that vendor and/or Veeam software may need tweaking, but hard to know where/how to escalate this.

Thanks
Jeremy

DGrinev
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Re: LTO8 Capacity

Post by DGrinev » Mar 19, 2018 4:26 pm

Hi Jeremy,

I did some research and according to the IBM knowledge base capacity of LTO-8 is 12TB, but only 11TB are usable.
Thus, I believe you see the real value of 10.8TB. Thanks!

jfnk1ng
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Re: LTO8 Capacity

Post by jfnk1ng » Mar 19, 2018 11:22 pm

Thanks Dmitry

Not 100% convinced by this. I can certainly believe you don't get the full 12TB (in spite of what the dashboard tells me), but the actual figure quoted in the Knowledgebase article is 11.18TB and Veeam is telling me 10.4TB. That's still a fair chunk missing, so there must be something else at work too.

Thanks
Jeremy

Dima P.
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Re: LTO8 Capacity

Post by Dima P. » Mar 20, 2018 10:42 am

Hello Jeremy.

Veeam B&R uses the metrics received from tape media (we read it’s chip). This information is used to estimate the tape size, free space, end of media etc. If you have an option, please open a case with your device vendor regarding the tape media capacity and let us know if you need any assistance from our side. Thank you.

jfnk1ng
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Re: LTO8 Capacity

Post by jfnk1ng » Mar 20, 2018 11:17 am

Thanks Dmitry

Not experienced Quantum support before, but I'll see what I can do...

Lunatic Magnet
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Re: LTO8 Capacity

Post by Lunatic Magnet » Apr 14, 2018 12:30 am

DGrinev wrote:Hi Jeremy,

I did some research and according to the IBM knowledge base capacity of LTO-8 is 12TB, but only 11TB are usable.
Thus, I believe you see the real value of 10.8TB. Thanks!
I have a Dell TL1000 LTO-8 library with the latest firmware (April 10 2018) and tapes are showing 10.9TB capacity. Looking at some older LTO-6 tapes which have 2.5TB raw, they come up as 2.3TB in Veeam. 2.3TB is 88.46% of the raw capacity. 10.9TB is 90.83% of the raw capacity.

I'd say that's pretty close, but unfortunately like the usable size of hard drives, the larger the tape capacity the more you lose. :x

tsightler
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Re: LTO8 Capacity

Post by tsightler » Apr 14, 2018 4:39 pm 2 people like this post

Lunatic Magnet wrote:I have a Dell TL1000 LTO-8 library with the latest firmware (April 10 2018) and tapes are showing 10.9TB capacity. Looking at some older LTO-6 tapes which have 2.5TB raw, they come up as 2.3TB in Veeam. 2.3TB is 88.46% of the raw capacity. 10.9TB is 90.83% of the raw capacity.

I'd say that's pretty close, but unfortunately like the usable size of hard drives, the larger the tape capacity the more you lose. :x
You're not really losing anything, it's just the conversion from terabytes, which is used by storage vendors to advertise capacity, to tebibytes, which is used by the OS (and Veeam as far as I know) to display capacity. The confusion comes in that they both use the same abbreviation of TB to refer to these two different things. Technically, I'd say it's the OS that is "wrong" since the abbreviation for tebibyte is TiB, but would anyone know what that is? Even if they did, technically it's the JEDEC 100B.01 standard that defines the "common usage" of KB/MB/GB uses power of 2 values, so it's not really wrong per-se. Basically, in common computer usage people know that a KB=1024 bytes, but storage manufacturers use KB=1000 bytes.

2.5 Terabytes = 2.27375 Tebibytes which rounded is 2.3 and thus is displayed by the OS as 2.3TB. For LTO8, that 12 terabytes = 10.9139 tebibytes which, when rounded, is displayed as 10.9 TB.

For a little deeper dive into the math, the LTO8 capacity is 12,000,000,000,000 (12 trillion) bytes. If you divide by 1,000,000,000,000 (one terabyte) then that's 12 terabytes. However, the computer uses 2^40 bytes which is 1,099,511,627,776 bytes (1024*1024*1024*1024 instead of 1000*1000*1000*1000). 12,000,000,000,000/1,099,511,627,776 = 10.91393642127514 tebibytes. Note that you still have all 12 trillion bytes, it's just the OS is displaying tebibytes instead of terabytes.

It's probably easier to just use Google to convert between them, 12 terabytes is equal to 10.9 tebibytes.

jfnk1ng
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Re: LTO8 Capacity

Post by jfnk1ng » Apr 24, 2018 8:03 am

Thanks all for your replies in this. Quantum support didn't really add to the conversation - just sent links to the specs and user guide which reiterated 12TB as the capacity.

The terabyte v tebibyte thing is interesting. I know there is an increasing tendency to use trillions rather than 1024^4 when quoting TB so that definitely rings true.

Cheers
Jeremy

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