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Question 6 node network raid 10

Ivanbre
Frequent Advisor

Question 6 node network raid 10

Hi,

I got the following question:

Say i'm running a 6 node cluster of p4000.

I'm using raid 5 vor hardware level and network raid 10 for my volumes.

1st question:

Does it mean when i have network raid 10 my data only is written twice on two nodes? If so what happens if these 2 nodes in my 6 nodes cluster fail both at same time?

2nd question:

if i wont to expand my p4000 cluster. Do i have to have the same capacity as rest or doesn't it matter what capacity i purchase?
3 REPLIES
Mark...
Honored Contributor

Re: Question 6 node network raid 10

Hi,
1: 6 node cluster using N-10 then the same data blocks are written twice but it is written across all the nodes in the cluster:
1= AF
2= AB
3= CB
4= CD
5= ED
6= EF

2: If you add another node into your cluster then it should be the same or greater capacity. Can you add a smaller node? Well maybe depending on how much capacity has been used in the existing capacity.
For example:
3 nodes of 10TB = 30TB total
1 node of 10TB and 2 nodes of 20TB = 30TB total. The reason for this is that in a cluster the SAN/iQ s/w will default down to the size of the smallest node in a cluster. The rest of the space will be "lost" until all the nodes in the cluster are the same capacity.

Mark...
if you have nothing useful to say, say nothing...
Ivanbre
Frequent Advisor

Re: Question 6 node network raid 10

Hi Mark,

So what happens if node 1 and node 2 both fail.

I lose the written block A and A on both nodes? so i lose data right?
teledata
Respected Contributor

Re: Question 6 node network raid 10

True, in Network RAID 10 you could sustain data loss with the failure of 2 or more nodes.

As redundancy, and availability demands increase you can change the replication level (on a per volume basis).

You can go to Network RAID 10 +1 like this:

1= AD
2= AB
3= AB
4= CB
5= CD
6= CD

Now you can sustain a 3 node failure. You can go as high as Network RAID 10 +2.

Of course you are trading higher availability for storage usage/efficiency, but the nice option is that this choice can be made on a volume by volume basis..
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