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I have two servers (attached disks have been set up as hardware RAID1 for disk device level failure resilience).

Here is the setup in my mind:

1) Install ESXi on each of the physical server, M1, M2;

2) Start one VM on each of the ESXi virtualized physical server V1, V2;

3) Install the DRDB drivers within V1 and V2.

Essentially, this is a "virtualizing machine running DRBD in the VM's instead of bare metal hardware" idea.

My question is whether the above setup can achieve the same "networked RAID1" goal that DRDB can achieve in the bare-metal physical machines (http://www.drbd.org/).

Thanks.

[EDIT] I found this (http://serverfault.com/questions/49305/drbd-experimentation-and-virtualization) is a similar question, but the answer does not seem to be firmative enough for me to follow.

[EDIT 2] One thing I need to understand is whether the DRBD driver inside the VM got the "Ok, data flushed to local disk" echo means "the data has been flushed to underlining physical disk". Because I want to consider corner situations like 'split brain problems'

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2 Answers 2

up vote 2 down vote accepted

My question is whether the above setup can achieve the same "networked RAID1" goal that DRDB can achieve in the bare-metal physical machines.

Yes, very easily, just forget that they're VMs, it makes no difference (other than a slight performance drop) whether they are or not.

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Thanks for the prompt answer. Are you saying the ESXi virtualization layer impose a write-through policy? i.e., the DRBD driver inside the VM got the "Ok, data flushed to local disk" echo means "the data has been flushed to physical disk"? –  chen Sep 18 '12 at 21:38
    
Yep, that's right. –  Chopper3 Sep 18 '12 at 21:51

We do it here quite often. There's no difference. The fact that you're using virtual machines is incidental.

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"... is incidental" what does this mean? One thing I need to understand is whether the DRBD driver inside the VM got the "Ok, data flushed to local disk" echo means "the data has been flushed to physical disk". Because I want to consider corner situations like 'split brain problems' –  chen Sep 18 '12 at 21:42
    
Time to pull out this one: i.stack.imgur.com/HDDKa.jpg –  Mark Henderson Sep 18 '12 at 21:55

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