RAID1 hardware

[marmellata]

Hi, sorry but I'm still a new user of VB and virtualization in general, so I have a doubt if VB fits RAID1 hardware. I have 2 hot-swap HDD - SAS, RAID should be hardware not software.
SERVER: HP ProLiant ML310 G4 - Server - tower - 5U - 1 via - 1 x Pentium D 945 / 3.4 GHz - RAM 1 GB - SAS - hot-swap 3.5" - HDD 2 x 72 GB - CD - ATI ES1000 - Gigabit Ethernet.

[vbox4me2]

A Guest VM harddisk sits in a Host real harddisk, that one can be anything including raid. Guests can not use direct raid access from the Host.

[marmellata]

I see, so it means that if one HDD fails VM works on the other one, right?

[vbox4me2]

Correct, the Host 'hosts' the VM files on the Host raid.

[marmellata]

ok, new problem.. hope you can help me, last time I installed VM on a IDE HDD and it was fine, now what should I use? VBoxManage addiscsidis ? actually I have SAS HDD - Serial Attached SCSI. How can I build it? ..if it is possible

[vbox4me2]

You have to understand how a Host works, the underlaying storage solutions are only accesseble by the Host, remote storage can be used by Guests. The VM HDD sits above any storage layer. If you want something else you need to be more specific.

[marmellata]

last time with IDE HDD in my headless server I used:
VBoxManage createhd --filename "srv2.vdi" --size 30000 --remember
VBoxManage modifyvm "server2" --hda "srv2.vdi"

but now I have SAS HDD.. I think it is why now I get this error:
VirtualBox Headless Interface 2.2.4
(C) 2008-2009 Sun Microsystems, Inc.
All rights reserved.

Listening on port 3389
Segmentation fault

Reading the manual I found three different hard disk controllers: http://www.virtualbox.org/manual/UserMa ... ontrollers

[marmellata]

but I have no idea if it is possible to set up SAS controller, shall I use SATA or SCSI controller..

[vbox4me2]

Since its all emulated it makes little difference what you choose, sata works fastest as far as I've seen given the proper Guest drivers.

[HolgerB]

@marmellata:
It seems to me that you have a problem with the general understanding of a way a RAID/SATA/SCSI drive (or set of drives) is attached to a system.

The host system itself controls the access to the attached harddisks. So unless we use iSCSI targets as VBox harddisks it really doesn´t matter which underlying system you use to store the VBox harddisk files on it.

No matter if it´s a
- software raid
- NFS share from a NAS mounted to a specific path
- SAMBA share mounted to a specific path
- iSCSI target mounted to a specific path via Linux iSCSI initiator and formated with a filesystem

Is this understandable for you ?

So if you have two SAS drives (2x 72 GB in your case) attached to a hardware RAID1 controller,
they will be most likely visible to the installed Linux as on 72 GB HDD (at least for my understanding).
So if one HDD will fail your RAID1 controller should be able to reconstruct the disk as soon as you replace
it by a working HDD. For such purposes hot-swap HDDs work perfect

All this is done at hardware level without any OS involved.

>I see, so it means that if one HDD fails VM works on the other one, right?
Well, not shure. The RAID implementations I know (RAID5) would allow such a behaviour. Not shure what sort
of reconstruction your RAID1 controller allows ?!?

[marmellata]

Ok I see the difference in levels from hardware to OS, the problem was I got that error so I thought maybe there was something wrong the way I managed the hosted server's configuration. I was curious to understand why, so I installed xorg and tried with GUI, actually now it works. I just have to understand why it didnt work before, after that I will remove xorg.

thanks