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My disk arrays amount

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rustam_2
Super Advisor

My disk arrays amount

Hi all,
i would like to determine how much is my disk arrays size on EVA. I have 10 disks on my disk controller and each one's size is 146 GB.
So total disk amount is 10*146= 1460 Gb
But on EVA in Storage Capacity area i see:
Total: 1365 Gb
Used: 1184Gb
Available: 181 Gb

Q:
1. I think total amount should be 1460 Gb but why VA shows me 1365Gb?

Before redundancy size were 300Gb but now is 181Gb. Will it become lower and lower?

Regards,
Rustam
9 REPLIES
DeafFrog
Valued Contributor
Solution

Re: My disk arrays amount

Rustam ,
you should post this in relevant sub segment of this forum.
this disk capacity that you see in available capacity is influenced by the spare disk "single" or "dual" protection that you have set.
Also your 146 gb disk are actually 135.9G, if you have kept say double protection for the virtual disk group , then further take out approx 2.5 % from each of your disk,and not to forget the space reduction with the chossen raid level.

check if that add out/ rounds off to what you see.

Regards,
FrogIsDeaf
Rita C Workman
Honored Contributor

Re: My disk arrays amount

146Gb is the 'actual' size of the disk.

But that physical disk is then carved up to size you want to see presented into logical disks.
Configuring the physical disk to become multiple logical disks requires a measure of overhead. And what the total impact that has against the size used for overhead depends on how you "carve" it up.
Generally if you carve up into smaller sized logical disks to get more disks it takes more overhead.
By reverse, if you carved up into larger logical disk size resulting in less amount of disk it takes less overhead.

Regards,
Rita
Rita C Workman
Honored Contributor

Re: My disk arrays amount

Sorry, I forgot to mention the next impact is the RAID you selected.
For example RAID5 will take at least (3+1), so you will see as usable the 3 disks, but you lose the 1 disk to parity.
If you went for mirrored disk, then you just half of your disk as usable storage to mirroring.

/rcw
P Arumugavel
Respected Contributor

Re: My disk arrays amount

hi rustam,

Always the disk will not have the full capacity for usage.
As DeafFrog said, the disk will have the real value to less than 146GB (app 136GB)...
So for 10 Disks, it is around 95GB less value from the actual value...

Rgds..
Uwe Zessin
Honored Contributor

Re: My disk arrays amount

No, this difference in numbers has *nothing* to do with 'metadata' or 'VRAID' overhead or the EVA's so-called "protection level".


That is just the difference between "HardWare GigaBytes": what is written on the disk drive: 146GB (if you look at the number of blocks, you'll see that it is a bit larger - see below)

and "SoftWare GigaBytes": what is shown in Command View EVA. You see that on other storage arrays or on operating systems as well.


From a real-life EVA:
according to SSSU, a BF1465A693 disk drive has 286749488 blocks of 512 byte each.

That makes 286,749,488 Blocks * 512 Bytes/Block
= 146,815,737,856 Bytes

Most humans calculate
146815737856/1000/1000/1000 = 146.815
which gives about 146.8 HWGB

(1000 is 10^3)

The EVA does not calculate with base10.
It calculates: 146815737856/1024/1024/1024
(1024 is 2^10)

Which gives about 136.7324 SWGB per disk drive.


There is no capacity lost!
It is the same as when I write: 5 = 101

Oh, I meant:
5(10) = 101(2)
;-)
.
Maxitaly_1
Advisor

Re: My disk arrays amount

Hi all

I think that the Total in Storage Capacity is the sum of the Total of all the disk groups.
But the total of a disk group (in CV: specific disk group, TAB General, section Capacity) I think that includes the spare level.

My example: EVA 4100, CV 9.01.00.090604, FATA disk group, 8 x 500GB FATA.
In Disk Group: Total=2793 GB - spare level=1 (2 disks reserved)
So: 2793/(8-2)=465.5 GB each disk
And (see Uwe post): 465.5*1024*1024*1024=499826819072 bytes
OK HD is 500 GB

Rustam: do you see 1365 GB in Total ? But your spare level ? Maybe is 0...

Max
rustam_2
Super Advisor

Re: My disk arrays amount

How i can determine my spare level? and raid for EVA? because here are 3 raid levels shows EVA - vraid0 - 117 Gb, vraid1 - 58 Gb, vraid5 - 94Gb and vraid6 - not available

Now a bit confusing is here also. My disk arrays' is used by 2 servers. First server has 3 presentationed disks (mounted points) and second server has 4 presentationed disks(mounted points). The sum of first servers mounted pointed is 330 Gb and second server's 540Gb.
So 540Gb+330Gb=870Gb values are used from EVA. But my EVA capacity is 1365GB.where are other Gbs?

Sorry if i'm asking stupid question. But i need make report and then if we will see whole problem , buy new disks or ...

Regards,
Rustam
Maxitaly_1
Advisor

Re: My disk arrays amount

Hi

CV has an online help...

The essential informations are in CV, specific disk group.
The spare level is "Disk drive failure protection".

The raid level is specific for each LUN.

Capacity: see attach. In my example, 2793 GB (spare level 1, see my previous post). The row vraid5=593 GB states that I can create a LUN of 593GB (max) in vraid5. But if I create a LUN in vraid0 the LUN is 741 GB. Obviously the raid uses storage space for redundancy...

Max
rustam_2
Super Advisor

Re: My disk arrays amount

Hi all,
Now i understood why my EVA shows me 1366 GB. Coz each my disk's actual size is 146.7 Gb but software size is 136.73 Gb. As Uwe mentioned above it's software gigabyte. My protection level is 'Single'. So 2 disks are reserved but why i see 1366 Gb - (2 disks)= instead 1366 - 273.46 = 1092.54 Gb?
I also determined that my LUN's raid is RAID5.


Regards,
Rustam