SAN/iQ 9.0 NR-5 - cluster of 12 nodes

[RemyZ]

Hi,

I understand how data is striped across nodes in a NR-5 volume, when 4 nodes are used. (SAN/iQ 9.0 manual, november 2010, page 195).

Did I understand correctly that when using a 12-node cluster (for that sake: a cluster with 7 of more nodes), there is 1 parity stripe per 4 data stripes? Or am I missing something here?

When looking at the latest HP P4000 SAN Solutions user guide (november 2010), I really think it presents incorrect information. It states on page 191 that one can use NR-5 with at least 4 nodes. According to this, one can use NR-5 with only 3 nodes.

On page 194 it's also stated that when creating a NR-5 volume, a basic snapshot schedule is created as well. This is not true either right? Starting SAN/iQ 9.0 snapshots are not needed anymore?

-Remy

[Emilo]

The new release notes touch on both these points

P4000 SAN Solution software release notes

http://bizsupport2.austin.hp.com/bc/docs/support/SupportManual/c01886197/c01886197.pdf

Look on page 4

Enhancements
The 9.0 release is a comprehensive release that includes enhancements in the following areas:

• Network RAID 5 and 6 enhancements — No longer require snapshots, Network RAID 5 on clusters
of three or more, Network RAID 6 on clusters of five or more

[RemyZ]

The release notes only show that the manual indeed containts false information; it should be updated.

I still would still like to know though how data and parity blocks are divided over the nodes in a >= 7 node cluster. I think I know, but if someone could confirm my idea it would be nice.

[gdubjr]

Hi Remy,

It looks like the manual contains artifacts from SAN/iQ 8.5, when 4 node were required for NR5.  With SAN/iQ 9.0, only 3 nodes are requred for NR5.  It is a variable stripe and parity up to 5 nodes.  i.e. 3 nodes is 2+1, 4 nodes is 3+1 and 5 or more nodes is 4+1.

Snapshots are no longer required with 9.0.  A hidden snapshot is generated and deleted automatically by SAN/iQ when needed to encode all but the latest 10GB or 10% of the volume.

Good catch. I will make the documentation team aware of the concern.

Best regards,

George