[Linux-HA] Raid and drdb

[Claus Denk]

Hi all,

we have now almost configured our hardware for a HA cluster. We will use 
two IBM 3550 M2 servers, and I would like to ask you if you could share 
some experience about different disk configurations.

1) Using drdb, is having some hardware RAID on both machines good 
practice (for example 3 disks with RAID 5) or is it not necessary to do 
so as drdb is our network raid? I guess in case of failure of the drdb 
communication it would be good to have some additional raid security on 
each server. Does it affect the write performance a lot?

2) This machine has a maximum of 4 SAS slots, what would be good 
practice to install OS and data (2+2 disks with raid 1, or everything on 
3 disks raid 5, o 4 disks raid 10?) Of course disk price is an issue, we 
would like to have 500 GB of data, which requires 3 300 Gb disks for raid 5.

Thank you very much for any experience you can share!

regards, Claus