topic Re: EVA 4400 space calculations in Disk Enclosures

EVA 4400 space calculations

eltawansy — Wed, 15 Jun 2011 10:06:59 GMT

My company has EVA4400 with 8 FATA 1TB and 10 FC 450GB
i made 5 virtual disks
2 for the FATA disk group with size 1600 and 2048 GB
3 for the FC disk group with size 200,100 and 1000 GB
i m using RAID5 for all of them

i want to know what remaining space on both the two disk group with calculations please

i m using single protection level
and the alarm is set to 90%

i m confused cuz wen i tried to calculate it i got different numbers that i can see on my command view

thanks for the help in advance

Re: EVA 4400 space calculations

Johan Guldmyr — Wed, 15 Jun 2011 10:55:43 GMT

Hey, let's see if I get it right:

For the FATA:

with 8 disks of 1 TB , that will get you one disk for parity.

So 7TB. And then with single protection that will take away two disks, so 5TB.

Something around 5TB is what you should have available with no disks. Minus the 1.6 and 2.048 that's 1.3TB free. In that area anyway, around 1.2TB is what you should have free in the FATA disk group.

The alarm % is just for alarm.

What is your occupancy/total space now?

Sometimes it's different if there is reconstruction, levelling going on. It can also get wrong with some versions of the code/command view, but I haven't seen that much on the 4400.

Re: EVA 4400 space calculations

eltawansy — Wed, 15 Jun 2011 11:13:00 GMT

the space available for me wen i try to create new Vdisk is 1019 GB Vraid0 and 815 GB Vraid5

i want to know how i got 815 GB only ?

so please if u can tell me the calculations for this issue

another thing is wen i try to see available space on the disk group i find only 716 not 815 !!!
can u explain this please

Re: EVA 4400 space calculations

Johan Guldmyr — Wed, 15 Jun 2011 11:25:30 GMT

If you could attach the controller configuration dump to the post - maybe somebody (with access to an HP tool) can get you an explanation.

Re: EVA 4400 space calculations

Uwe Zessin — Wed, 15 Jun 2011 18:21:25 GMT

Disk sizes printed on the disk drive are in HardWare GigaBytes while Command View EVA shows SoftWare GigaBytes.

I don't know if a "1TB" disk has exactly 1000 Gigabytes or a 450GB disk has exactly 450 GigaBytes, so the following calculations are not exact and there is always a bit overhead that I don't have in the formula. But you could open the disk properties pages and show us the SWGB values from CV-EVA.

FATA disk group:
(6*1000/1.024/1.024/1.024)- ((1600+2048)*1.25) = 1027.9354

FC Disk Group
(8*450/1.024/1.024/1.024)- ((200+100+1000)*1.25) = 1727.7612

I have removed two disk drives from the calculation to account for the so-called "protection level".
That gives 6 or 8

"/1.024/1.024/1.024" converts from HWGB to SWGB

"*1.25" accounts for the VRAID-5 overhead
(it is 4D+1P, NOT one disk drive)

> the alarm is set to 90%

The occupany alarm is just a level after which a warning is given out. You could set it to 100% and the EVA will keep on working fine. Or set it now to 1% and the EVA will keep on working fine.

Re: EVA 4400 space calculations

Johan Guldmyr — Thu, 16 Jun 2011 04:02:30 GMT

>>This:

FATA disk group:
(6*1000/1.024/1.024/1.024)- ((1600+2048)*1.25) = 1027.9354

Is very close to the 1019GB eltawansy has, so looks very plausible. Rest is probably metadata.

Re: EVA 4400 space calculations

eltawansy — Thu, 16 Jun 2011 06:42:51 GMT

ya it seems that there is a little loss in the size of the FATA disk group

but wen u see for the FC disk group the space available is 1188 (i have one HDD of them failed) where the space should be 1308
(around 120 GB loss) is there any explaination for this ??

and about the issue that there is difference between the space i see on each disk group and the space available for me wen i create new VDisk
Is there any explaination??

one last thing wat is the way to get the controller hardware dump ??
i will attach the reports abt Vdisks,Disk groups and disk status

Re: EVA 4400 space calculations

eltawansy — Sun, 19 Jun 2011 10:06:29 GMT

i guess i found the controller configuration dump