High availability storage : raid1 of iSCSI or iSCSI + hast

[Solène Rapenne]

Hello,

I am building a high availability cluster with FreeBSD, to make it 
simple, we have 2 master/slave server called Web1 and Web2 and 2 
master/slave file server called iSCSI1 and iSCSI2.

I have been thinking about 2 options and I would like to have some 
feedback if you run one of the option (or something else) :
     - the first is to create a raid1 of both iSCSI target and mount it 
on the webserver who is the master.
     - the second is mounting the iSCSI target from the master iSCSI 
server and the master iSCSI server will replicates the data to the slave


1st option : MASTER Web connects to both iSCSI server and make
              a raid1 of the iSCSI

pros : in case of failure of iSCSI 1 or 2, Web isn't affected
cons : slow ? network bottleneck ?

    +---------+   CARP   +---------+
    |  Web1   |  <---->  |   Web2  |
    +---------+          +---------+
        |raid1\
        |      \__________
        |                 \
    +---------+          +---------+
    | iSCSI 1 |          | iSCSI 2 |
    +---------+          +---------+


2nd option : MASTER Web connects to MASTER iSCSI server,
             which replicates to slave iSCSI server with HAST

pros : no idea
cons : if we want to switch the iSCSI server we have to stop everything

    +---------+   CARP   +---------+
    |  Web1   | <----->  |   Web2  |
    +---------+          +---------+
        |
        |
    +---------+  CARP +  +---------+
    | iSCSI 1 |   HAST   | iSCSI 2 |
    +---------+  <---->  +---------+


Thank you for reading