Requested level: single hids 2 drives

[Jeffrey S. Jalbert]

Having just installed 10 1 Tb drives on an EVA4100 and configuring them into a single disk group, I was suprised to seee that the avaliable capacity was about 7.5 Tb with no vdisks assigned.

The disk group is configured with drive failure protection level "single" and occupancy alarm at 90%.

This combination of factors seem strange to me. When I change the requested level to "none" I immediately get back almost 2 Tb (2 disks) worth of space.

So what gives here? If I configure raid 5 AND I have an occupancy alarm level of 10%, why does command view ALSO hide 2 drives from me?

Also, what is wrong with making the requested level none if I am careful to observe occupancy levels?

thanks

[IBaltay]

Hi,
single disk protection means 2 virtual spares, it is not a good idea not having them (none) because then immediately after the disk failure the whole disk group becomes into the degraded state. If you have 2 virtual spares, the controller firmware automaticaly ungroup the failed disk from the disk group and the disk group is again ready to survive the one disk failure....

[marsh_1]

hi,

take a look at this thread , it should help explain those numbers.

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1263523&admit=109447626+1245284945476+28353475

hth

[Jeffrey S. Jalbert]

O.K. I understrand the idea of spares, but with the spares being reserved, why should I be concerned about occupancy levels? Why not just run it up to close to 100%?

[IBaltay]

to have space for the metadata operations like the leveling, group/ungroup, etc.