topic Re: Disk Sparing in MSA Storage

Disk Sparing

Simon Powell — Wed, 22 Mar 2006 11:32:48 GMT

I'm leaving my current role and the person who is taking over from me doesn't understand disk sparing, I've tried explaining but they are having trouble understanding it. Is there any documentation on the HP website that explains disk sparing on an EVA 5000.

Re: Disk Sparing

Steven Clementi — Wed, 22 Mar 2006 12:09:37 GMT

Simon:

How did you explain it? (just curious)

Make sure your replacement understands that the storage is ALL virtualized. It is NOT like traditional storage.

Single Sparring = the amount of space of 2 drives in a Disk Group is "reserved" and set aside for usage when disks fail. If the disk group is a mix of disk sizes, the LARGER of the sizes is used to calculate the "reserved space". The reserved space is just like a virtual disk in the sense that it is spread across all the available drives in the group. It is not any particular disk that "gets swapped" during a failure.

Double Sparring is the same except that it is the amount of 4 disks, not 2.

I believe there is a doc somewhere, but am unsure of the link at the momemt. Someone will probably post one.

Steven

Re: Disk Sparing

Sameer_Nirmal — Wed, 22 Mar 2006 15:29:18 GMT

Hi Simon,

The Disk Sparing in EVA is documented in the best practices document at
http://h71028.www7.hp.com/ERC/downloads/5982-9140EN.pdf

Re: Disk Sparing

Arch_Muthiah — Wed, 22 Mar 2006 16:54:29 GMT

Simon,

A brief intro on disk sparing:

The EVA3000 utilizes active sparing for data protection. The spare space for disk failure protection is actually spread across the virtual disk. This provides instant availability to the EVA to transfer data from an ailing drive and insures that there is no possibility that the disk spare could go bad, leaving you without spare protection.

Archunan

Re: Disk Sparing

Arch_Muthiah — Wed, 22 Mar 2006 16:57:50 GMT

Simon,

And
EVA disk sparing determines the amount of spare space that is reserved to rebuild a failed drive.
There are three sparing levels:
1. Zero â No space is reserved for the drive rebuild process.
2. Single â Capacity is reserved to rebuild a single failed drive.
3. Double â Capacity is reserved to rebuild two failed drives.

Archunan

Re: Disk Sparing

Uwe Zessin — Thu, 23 Mar 2006 00:49:56 GMT

> The EVA3000 utilizes active sparing for data protection.

And what is that supposed to mean?

> The spare space for disk failure protection is actually spread across the virtual disk.

Wrong - the 'protection space' is spread across the 'disk group'.