topic Re: disk on RAID in Disk Enclosures

disk on RAID

H4Dy — Wed, 10 Jun 2009 06:20:27 GMT

Hi all,

When i create a new vdisk, can i see the disk that is used on EVA 4400?
How can i make sure the pair of RAID 1 using different disk at EVA?
FYI, i only create 1 disk group.

Thanks,

Re: disk on RAID

Patrick Terlisten — Wed, 10 Jun 2009 07:06:19 GMT

Hello,

this is done by the controller firmware. The process is much more complex, but the controller will pair two disks together to store VRAID 1 data. The data on a VRAID 1 disks is definitely stored on two different disks. Depending on the number of enclosures and disks, those two disks are located in different enclosures, but in one disk group.

Hope this helps.

Best regards,
Patrick

Re: disk on RAID

Uwe Zessin — Wed, 10 Jun 2009 11:00:11 GMT

The data for a virtual disk is distributed across ALL physical disk drives in a group. The VRAID-level defines how the redundancy is layed out. As Patrick already wrote, this is a quite complex. In case of VRAID-1, the controller firmware indeed makes sure that two copies are stored on two different physical disk drives.

And please note that there is NO redundancy for VRAID-0! No matter what you get told about virtualization, the so-called 'protection level', RSS, RSTORE, bla bla bla...

Re: disk on RAID

Wickedsunny — Thu, 11 Jun 2009 02:41:30 GMT

The RAID concepts in terms of virtual raids are somewhat different than the normal RAID world. Hence, I would suggest you a few reads before you start working on this BOX. If these features are used efficiently then you can get much more out of the EVA.

I have attached a White Paper on this. Please go through it and you will have a better idea on how things work on EVA's

Regards,
Sunny

Re: disk on RAID

H4Dy — Thu, 11 Jun 2009 04:16:47 GMT

Hi all,

thanks for your responses.

Btw, what is purpose for disk drive failure protection at EVA? Is it used to for redundancy too?

Thanks,

Re: disk on RAID

Uwe Zessin — Thu, 11 Jun 2009 05:33:10 GMT

Not at all - think of it as a virtualization of spare disks. The idea is to put data on all available disks so all disk can be used for I/O, but still have disk space available to rebuild redundancy after a disk drive has failed.

Re: disk on RAID

H4Dy — Thu, 11 Jun 2009 08:10:05 GMT

thanks