EVA5000 Presentable net space

[A.W.R]

Hi,

We have an EVA5000 that we have just filled with 250GB of FATA drives, i.e. 60TB of raw storage.

Deep in the EVA5000 help we have now discovered the following comment:-

The other, and more important space, is the Presentable or Net Space. This is the address space that can actually be used to address blocks on the system

and is used for LUN and Vdisk addresses.

For EVA3000/5000 this space is limited to

- 32TB (when base 2 is used ---> 1TB = 1024 GB = 1024 MB.....) or

- 35TB (when base 10 is used ---> 1TB=1000GB = 1000 MB....)

Can anybody clarify if this comment refers to per disk group, or per the total EVA?

Thanks
Andrew

[Mark Poeschl_2]

That figure is total for the EVA.

[Uwe Zessin]

Right. It is an upper limit constrained by the size of the physical 'policy memory' in the controllers which holds the mapping tables.

[chris callihan]

the key word there is PRESENTABLE. if you use raid-1, you would stay under that limit. the other part to watch out for is that snapshots and snapclones could make you go over that threshold even if you do use raid-1.

[Alzhy · Accepted solution]

As we've painfully found out, the MAXIMUM space you can carve out of your EVA 5000 regardless of how large of RAW space (total sum of all your Physical Disks) you have -- is ~32TB of Vdisks of whatever VRAID type.

HP Sales is not always aware of this fact and there've been several cases I know (including us) that bought additional enclosures/disks

[Alzhy]

cont:

only to find out we'll not be able to carve VDISKS anymore out of the capacity we bought because we already carved out 32TB worth of Vdisks.

I would think we're/the customer is partly to blame but HP Sales/Tech assessment team I think should make sure the customer is aware BEFORE agreeing with the purchase of additional capacity.

As an example:
Before our last purchase of 2 Shelves to max out our EVA5K to be a fully loaded 240 disk system - we already had about 40+TB of raw disk capacity with about 30 TB of VDISKS carved/presented (mostly VRAID5s). So we ut in our order for 2 shelves (24) of 500GB FATA Drives hoping we'll gain about 9TB of Space.

TO our surprise, we were only able to carve out an addiional 2TB of Vdisks and it won't allow us to carve our new Vdisks anymore!

It took a while for HP to figure out and acknowledge this limit -- desptite us having sent them our current configuration before the purchase and during the troubleshooting that followed...

The resolution was we'll possibly just buy a new EVA4000 chassis to house these 2 shelves of 500GB FATAs - hopefully for a very steep discount from HP. ;^)

[Adam Garsha]

True or False:

The EVA5000 32/35TB presentation vdisk limit doesn't care if I present the same vdisk multiple times correct? A vdisk only counts once against the limit, right?

I am asking about cluster impact here, if I have big LUNs presented multiple times that doesn't count multiple times against my 32/35TB EVA5000 addressibility limit (say it aint so).