Disk Arrays
cancel
Showing results for 
Search instead for 
Did you mean: 

EVA 5000: Vraid5 overhead

SOLVED
Go to solution
Pearl Park
Occasional Advisor

EVA 5000: Vraid5 overhead

I have a question about EVA 5000.
What is the overhead for VRAID5 redundancy ?
EVA InfoPak dated May 2003 says that Vraid5 consumes 1.25 blocks of physical capacity for every block of usable capacity.
However, when I see Command View EVA 3.1's(VCS version 3.010) report, it seems that Vraid5's overhead is 20 % of usable capacity, not 25 %.
Can anyone tell me what is correct ?
Thanks.
5 REPLIES
Uwe Zessin
Honored Contributor
Solution

Re: EVA 5000: Vraid5 overhead

Both are correct ;-)

4 data segments are combined with one parity segment: (4+1)/4 = 1.25

Assuming you have 100 'raw segments', then 80 segments will be used for data and 20 for parity: 100% / (4+1) = 20%
.
Steven Clementi
Honored Contributor

Re: EVA 5000: Vraid5 overhead

Pearl:

I can confirm that the VRAID overhead is @20%. On all the EVA's I have installed over the past 3 years, it's been @20%.


Steven
Steven Clementi
HP Master ASE, Storage and Clustering
MCSE (NT 4.0, W2K, W2K3)
VCP (ESX2, Vi3, vSphere4, vSphere5)
RHCE
NPP3 (Nutanix Platform Professional)
Pearl Park
Occasional Advisor

Re: EVA 5000: Vraid5 overhead

Thanks for replies.
Pearl Park
Occasional Advisor

Re: EVA 5000: Vraid5 overhead

Responses offer excellent explanation.
Now I have the correct formula to compute available space for Vraid5 disk.

Re: EVA 5000: Vraid5 overhead

You may have the correct formula for the RAID level but do not forget about the Hex to decimal conversion. Your 146GB harddrives actually only have 142GB or so in Hex. Hard drive maufacturers base their capacities on 1000MB=1GB not 1024MB=1GB in large RAID array's it make a big difference. Also read up on the EVA if you already haven't. Spare capacity works different and you should not exceed 95% of available capacity of leveling performance.