Network RIAD 10+2 (2-way or 4-way mirroring)

[alfa2008]

Hi,

We are installing 4 HP StoreVirtual 4000 in multi-site setup (2 remote sites), 2 storages per site. While configuring volumes, regarding Network RAID we can see few options, but I want to know:

1. Difference between 2-way or 4-way mirroring in Network RAID 10+2 (to use for multi-site HA)

2. Is it possible to configure some volumes only for intrasite mirroring (mirroring only 2 storages Network  RAID 10) while keeping other volumes mirroring between 4 nodes across sites. This configuration would be great to use for replication using application built-in tools.

Thank you

[oikjn]

you can change the protection level at the LUN level so you can have some LUNs at NR10 and others at NR10+1/2/3/ect, but unfortunately you cannot have LUNs on only one site, so best case, for LUNs you don't need 4 copies of the data on, you can do NR10, but that would mean you get one copy on one site and one on the other.  You would need at least one additional cluster if you wanted data only at one site :-/

BTW, multi-site setups are tough.  Just because the feature is there and you are licensed to do it doesn't mean you actually should do it.  Make sure to read the HP guides and follow the suggestions or you won't be happy.  In perticular, make sure you have the FOM at a THIRD site or there is little point in doing a true multi-site cluster.

[alfa2008]

If cross-site replication works with NR10, then what is the difference between NR10 and NR20 (in the scenario with 2 nodes per site), and what's the difference between 2-way or 4-way mirroring.

Thank you

[oikjn · Accepted solution]

NR10 gives you one copy of the data and NR10+2 gives you 4 copies.  The CMC help does a good job of explaining how it works (search "how data protection levels work" in CMC help).  Basically, in a multi-site cluster, NR10 will let any one node on either site go down or even a single site can go down, but if a site goes down and then one additional node goes down, your data avaiulability is lost.  This is considered site redundancy.  NR10+2 will let you lose a complete site AND additionally a node before you lose data availability.  This is known as Site+node availability.  It takes up a LOT of room as you have four copies of your data, but basically you get a NR10 group at each site for maximum protection.