topic Re: EVA 5000 raw capacity in Disk Enclosures

EVA 5000 raw capacity

Peter Hrzic — Thu, 03 Jun 2004 07:23:43 GMT

Hello,
can anybody please explain this to me:
I have an EVA5000 with 38 72GB disks and 11 146GB disks in one disk group with double spare capacity. Total storage space, shown in Command View, is 2982.53GB.
So if I do some simple calculation:
38x72GB disks (2736GB)
+ 11x146GB disks (1606GB)
= 4342GB total by disk cap.
- 584GB (4x 146GB double spare)
---------------------
= 3758GB (this, with metadata subtracted is capacity I beleive I should have)

There is, of course, capacity used for metadata, but how come, that I'm "short" for more than 700 gigs? Is it possible, that the metadata overhead is so big?

Does anybody know for a formula, how to calculate, how much raw storage you get with various upgrades (different disk sizes, etc..).

Thanks,
Peter

Re: EVA 5000 raw capacity

Sheldon Smith — Fri, 04 Jun 2004 13:59:09 GMT

While unsupported, the attached Excel spreadsheet provides a fairly good approximation of storage usage....

Re: EVA 5000 raw capacity

Mike Naime — Sat, 05 Jun 2004 00:55:11 GMT

As a general rule of thumb, figure that you are going to loose 30% of your raw capacity to overhead and sparing.

Actual practice shows that an EVA5000 with 240 146GB disks, and RAID-5 for VDISK selection, you are actually loosing about 26% to overhead/redundancy/sparing... Etc.

In the above configuration, I have 35TB of "RAW" SPACE if you do the math. I have 31TB reported as total space after turning on the EVA and initializing(formatting) the system. This is before I create any Vdisks at all. So, it looks like I loose 11% to formatting the drives. This might be explained by the 90% occupancy level that I have set on the system.

What is your occupancy level set to? This is also additional "Overhead" space that is reserved by the EVA for it's processing.

Mike Naime

Re: EVA 5000 raw capacity

Uwe Zessin — Sat, 05 Jun 2004 14:16:42 GMT

> What is your occupancy level set to? This is also additional "Overhead" space that is reserved by the EVA for it's processing.

It sounds like you are talking about the occupancy alarm level of a disk group. According to the online documentation it does not reserve any space - it specifies when an event code is generated. If you have a disk group with a total capacity of 100 GBytes and the level is 80%, then the code is generated when the group is filled with 80 or more GBytes of data.