# EVA Calculator?

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## EVA Calculator?

Hy!
Is there any tool or document to make an exactly calculation of my eva? or is there a document or guide with informations about the internal calculations of the hsv?

for instance, i have an eva3000 with 56x72gb disks, single failure protection level. when i configure vraid5's, i get an effective useable volumespace (when i add all volumesizes as they are seen from the OS) of about 68gb per disk. 4gb is a lot of an overhead and i would like to know, WHY!

regards,
wuhte
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Trusted Contributor

## Re: EVA Calculator?

Hi,

The algorithm for reserving protected space in the EVA is to find the largest disk in your disk group (72GB), double that size (2*72=144GB) multiply the result by your protection level (1 for you) and then remove that capacity from free space and distribute it across all the disks in the disk group.

144/56=2.57GB per disk

After that you have the cost of the Vraid5 virtualization...
Trusted Contributor

## Re: EVA Calculator?

Honored Contributor

## Re: EVA Calculator?

The size that is written on the disk drive is based on 10. The size displayed in the EVA's user interfaces (CV, SSSU) is based on 2.

When you create a virtual disk with '1 GB' you don't get room for 1,000,000,000 bytes - you get room for 2**30 = 1,073,741,824 bytes.

1,000,000,000 / 1,073,741,824 = 0.9313

The EVA reports a '72GB' disk drive with 68.36GB 'formatted capacity'.

68.36GB / 0.9313 = 73.402GB

(a StorageWorks SCSI disk drive has about 72.8GB - unfortunately I don't have a way to find out the exact block number of a FC disk drive attached to the EVA to verify that calculation)

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Here is some real life data:

I had initialized an EVA-3000 with one disk group, 8*72GB disk drives, protection level 0.

It reported a capacity of 546.40GB (8*68.36 = 546.88) - looks like 480MB reserved.

After I created two '5GB' VRAID-1 virtual disks, the capacity shrank to 526.31GB. That is 20GB raw capacity (2*5GB*2) for user data and 90MB reserved.

Next I created one '15GB' VRAID-5 virtual disk. The capacity shrank to 507.51GB. That is 38.75GB raw capacity (2*5GB*2 + 1*15GB*1.25) for user data and 140MB reserved.

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Please note that you should not max-out your EVA! It needs free space in it's disk groups to 'breathe'.

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I hope I got the calculations right and didn't just look like a fool...
Corrections welcome.
.
Honored Contributor
Solution

## Re: EVA Calculator?

Find attached the EVA Sizer written by Martin Casaulta. It is an unofficial tool but can help in planning EVAs either standalone or CAed.
I use it every time I plan a configuration!

Enjoy
Peter
I love storage
New Member

## Re: EVA Calculator?

I am also interesting in your calculator. But i Can't open your file.
Honored Contributor

## Re: EVA Calculator?

First of all, it is a ZIP file without any password containing an Excel spreadsheet ready to use!

Cheers
Peter
I love storage

## Re: EVA Calculator?

Thanx for posting the new version! What changes where made to the 3.2.0? Is the new licensing model of SOM already implemented?

kind regards,
wuhte
Honored Contributor

## Re: EVA Calculator?

The changes are minor:

To fix an internationalization problem (Excel versions in french, german, etc.) in the area of the export function!

Well, under SOM LTU the sizer shows the raw space an EVA provides. You can decide yourself how you want to license!
With the new SOM licensing you can either licencse one or multiple 1TB LTUs or unlimited LTU per EVA.

Hint:
For both the EVA3000 and the EVA5000 5x 1TB LTU is the same price as the unlimited LTU.

Cheers
Peter
I love storage