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 Post subject: TiB vs TB
PostPosted: Wed Jul 25, 2018 5:43 am 

Joined: Mon Apr 14, 2014 9:07 am
Posts: 165
Guys,

I'm hoping someone on here has a little more insight.

I've recently been making datastores of lets say 1TiB as the 3par works in TiB but i've recently been flagged up that we are billing a customer on what VMWare shows, which is in TB.

I'm sure i read somewhere before that a TiB on 3par is actually the same as a TB in VMWare, but i can't find that information.


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 Post subject: Re: TiB vs TB
PostPosted: Wed Jul 25, 2018 6:10 am 

Joined: Wed Nov 09, 2011 12:01 pm
Posts: 329
I don't look on VMware very often (since I lost my semi-admin rights and hence can't configure new LUNs for them anymore :roll: ) but generally most systems are rather lazy in the use of TB/TiB. I've seen tools/software on a single OS use both but only say "GB" so the only way to be sure is to look at the total size of the LUNs in that particular tool and just hope that it's consistent in that one tool at least.
I'm guessing you're using some VMware costing addon, I'd hope at least it would clarify which in the help docs if it's meant to be used for charging. ;)

Obviously used space is pointless as never the same between guest OS/VMware/LUN/raw, so can't really compare direct. We tend to lump all the differences under the term of VM Tax and add about 10% extra to charged LUNs for free if not RDM (we're moving away from these) however we almost never charge for 3PAR as no one here can afford it but do have other cheaper arrays for 'customers' needing TiBs of data (we are a Uni).


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 Post subject: Re: TiB vs TB
PostPosted: Wed Jul 25, 2018 9:16 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 917
Location: Europe
TiB is Base2, TB is Base10 and is a SI unit.

kiB = 2^10 = 1.024
MiB = 2^20 = 1.048.576
GiB = 2^30 = 1.073.741.824
TiB = 2^40 = 1.099.511.627.776

kB = 10^3 = 1.000
MB = 10^6 = 1.000.000
GB = 10^9 = 1.000.000.000
TB = 10^12 = 1.000.000.000.000

So the difference between TiB and TB is about 10%, so if you give them 1 TiB and invoice 1 TB you're giving them ~10% more than they're paying for.... But again if you're doing some form for thin provisioning it is only the Vmware numbers that seem to count for you. I would have your Vmware guy provide usage in bytes so there is no confusion :)

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 Post subject: Re: TiB vs TB
PostPosted: Thu Jul 26, 2018 3:08 am 

Joined: Mon Apr 14, 2014 9:07 am
Posts: 165
So as example, I've created a 2TiB volume from the 3par. It shows as 2097152 MiB but from an RV Tools export i see the size on the datastore as 2096896 MB so its not a huge amount of difference but it is different. If it was possible to create to the volumes in bytes then i could get it exactly right.

So basically want to look at billing the customer for exactly what vmware sees as the datastore size.


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 Post subject: Re: TiB vs TB
PostPosted: Thu Jul 26, 2018 4:48 am 

Joined: Wed Nov 09, 2011 12:01 pm
Posts: 329
That looks like a formatting difference, i.e. VMFS has absorbed a little space for admin reasons/block alignment etc. They appear to be both MiB at least in those examples.

Charging can get tricky, you can't use 100% of the VMFS volume as it needs space for VM snapshots etc. Then if you are considering used space charging you have a lot of factors, VMFS used vs OS used vs 3PAR thin used vs 3PAR compressed used vs 3PAR dedupe used vs 3PAR raw used etc.

Throw AO in there too... :?

I tend to just use an average to come up with a basic figure and apply that on a VV size but as I say we've don't charge out 3PAR, it's just for internal tracking and putting a usable figure for that odd occasion when someone wants 10TiB and has the cash. ;)


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