topic Re: Difference between VA and EVA in Disk Enclosures

Difference between VA and EVA

Vipul_2 — Tue, 10 Aug 2004 06:12:14 GMT

Hi Guys ,

Other than RAID levels and max storage capacity .. whats the major difference between ..say VA7xxx and EVA series(Say EVA3000) of products?

both are end-to-end Fibre

Regards ,
Vipul Bhadra

Re: Difference between VA and EVA

Slawomir Gora — Tue, 10 Aug 2004 10:01:03 GMT

Hi,

1. In VA74xx you have one (VA7110) or two (7410) redundancy group and one raid level for all of them - EVA has disk groups which can have different raid level-s
2. EVA has Continuous Access
3. EVA has Snapshots and Snapclones

etc...

Re: Difference between VA and EVA

Uwe Zessin — Tue, 10 Aug 2004 11:50:45 GMT

No, sorry. A disk group on the EVA does not have a VRAID level associated with it. VRAID is a characteristic of an individual virtual disk, which is the container for the user's data. You can have multiple virtual disks with different VRAID levels in the same disk group.

Re: Difference between VA and EVA

Steven Clementi — Tue, 10 Aug 2004 16:06:27 GMT

But the EVA has RSS athe the Disk Group level, which is sort of like RAID5 protection in theory, but not exactly the same.

Not sure if the VA has RSS.

Steven

Re: Difference between VA and EVA

Vipul_2 — Tue, 10 Aug 2004 22:53:05 GMT

Sorry .. but i could not understand what was being said. From what was said i assume the difference is that EVA has virtual raid.

IBM fastt groups disks in arrays out of which virtual disks are made out (Each array has one raid level .. say RAID 1,0 or 5 ).. and then logical disks are created in this array. Each of this logical disk can be assigned to a controller.

Do both VA and EVA operate similarly?

Are there any document(Other than quickspecs..say userguide) which will simplify things for me?

Thanks for the help.

Regards,
Vip

Re: Difference between VA and EVA

Rithu Kumble — Tue, 10 Aug 2004 23:23:10 GMT

Hi Vipul

Access this link to view all the documents for VA
http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?contentType=SupportManual&locale=en_US&docIndexId=179911&taskId=101&prodTypeId=12169&prodSeriesId=89018.

Also, the following link will take you to additional information for VA:
http://h20000.www2.hp.com/bizsupport/TechSupport/Home.jsp?%20locale=en_US&prodTypeId=12169&prodSeriesId=89018

Access the following link for documentation on EVA 5000
http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?contentType=SupportManual&docIndexId=3124&locale=en_US&prodTypeId=12169&prodSeriesId=321347

Access the following link for documentation on EVA 3000:
http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?contentType=SupportManual&docIndexId=3124&locale=en_US&prodTypeId=12169&prodSeriesId=315127

I hope this helps.

Regards
Rithu Kumble

Re: Difference between VA and EVA

Uwe Zessin — Wed, 11 Aug 2004 00:40:26 GMT

Steven:
No, I don't think so. A RSS is used to limit a failure domain. VRAID-5 stripes (4D+P) never span two RSS I have been told. So if you have two RSS, you can withstand one disk failure per RSS = 2 disk failures per disk group.

It's been too long that I looked at the inner workings of the VA to remember if it has something like RSS. By default the VA uses striped mirrors, but it can be switched to AUTORAID mode. In that case the array decides what data to store as RAID5DP (DP = double protection, so it can tolerate the failure of two disks).

Vipul:
The EVA and the VA do not work like the IBM. From the description it sounds like you create a disk array and this one is initialized with a RAID-level. Then you partition this container into multiple logical disks.

On the EVA you bind multiple disks together to form a disk group. This is a storage pool out of which you can draw capacity for your virtual disks. I have already written above that you can have different virtual disks with different VRIAD levels in the same disk group.

Re: Difference between VA and EVA

Steven Clementi — Wed, 11 Aug 2004 06:04:40 GMT

"A RSS is used to limit a failure domain. VRAID-5 stripes (4D+P) never span two RSS I have been told. So if you have two RSS, you can withstand one disk failure per RSS = 2 disk failures per disk group."

That is exactly how I understood the technology to work, except that I did not go into detail.

Steven

Re: Difference between VA and EVA

Uwe Zessin — Wed, 11 Aug 2004 06:31:02 GMT

Hello Steven,

my apologies, but that is not what I had read from your description. You wrote that RSS 'is sort of like RAID5 protection in theory'.

RAID-5 is about redundancy, protecting data from a (single) disk failure.

RSS is about failure domains within one EVA disk group.

Re: Difference between VA and EVA

Steven Clementi — Wed, 11 Aug 2004 10:07:39 GMT

which is why I also said... "but not exactly the same."

I really need to take the time and xplain myself better. Unfortunately, I sometimes quickly answer with little time to actually post a full message.

Sorry for the confusion.

Steven