Vdisk Size and Disk Spindles underneath on EVA 5000

[rccmum]

Guys,

I do appretiate all your replies here.

So far I have understand that...
Vdisk - Virual Disk is logical structure/concept. Being virtual , a Vdisk is not limited to a group of physical Disk or spindles like DG does. Hence when we create a Vdisk , a space would be allocated from bunch of disks virtually. Now when you actually start using Vdisk space, EVA will always try to put data across all spindles it can have in a DG using the fixed Vdisk chunk size.
Thats why they say having 1 DG is always recommended for good performance so that there are many spindles available to EVA
( EVA is hungry for Disk spindles!!!! )

Uwe has said it rightly...

Now with all above , I still wonder about "sweet spot" ( 56 disks ) and "bad spot" ( 168 Disks ) for EVA (both marked by
HP) ???

Peter , can you comment on this pls?

[Bill Costigan]

Just one minor point...

A vdisk is created in a disk group and therefore the number of spindles the vdisk spans is the same number of spindles in the disk group. (A vdisk cannot span disk groups) So creating a big disk group also leads to giving all the vdisks created in it lots of spindles to use,

[Uwe Zessin]

Isn't it interesting that 'sweet spot' #1 (56 disks) is the maximum disk number supported by EVA3000/4000 and #2 (168 disks) is an EVA 5000/8000 2C12D that still fits into one cabinet?

[Ivan Ferreira]

As far i know the RSS is used for parity calculations.

Redundant Storage Sets are subgroupings of drives, usually from 6 to 11, within a disk group to provide failure separation.

For example, if a disk group has two RSSs, a drive can fail in both RSSs and we will till have VRAID5 and VRAID1 availability.

So, theorically, if you have luck enough, you can have two disks lost in a VRAID5, if the failed disks are in a different RSS.

[rccmum]

Thanks Everyone for your time replying to the thread, appretiated...

[rccmum]

Thanks