CentOS

Hello everybody.
If anybody has this server, could you, please, tell me:
In my situation i set up onboard raid to mirroring (raid 1) and when server is running i am trying to take one hdd out and server stoppes responding. Stick it back into the bay and after 20 secs it starts responding again.
Whats wrong with raid 1 on this supermicro? Mirroring suppose to keep one hdd running and responding but it doesnt do so.
Did anybody ran into this kind of error before?

Server info: http://www.supermicro.com/Aplus/system/1U/1011/AS-1011M-T2.cfm
Motherboard info: http://www.supermicro.com/Aplus/motherboard/Opteron1000/MCP55/H8SMi-2.cfm
On-Board Devices

SATA nVidia MCP55 Pro SATA2 3.0Gbps Controller
6 SATA Ports
nVidia RAID 2.0
SATA RAID 0, 1, 0+1, 5, JBOD Support


Beforehand thanks

The raid of mcp55 does depend on 'dmraid', doesn't it? Thus, your question should be: "Why dmraid-based software raid fails to fail gracefully?"

We have run into this type of thing where I work. We don't have that specific model server, but we use SuperMicro and found that the on board RAID controllers for some of the lower end servers are actually BIOS RAID or "Fake" RAID. Essentially, this type of RAID does not have a true RAID chip and requires software drivers to assist the OS in performing RAID operations. Windows Server performs this task just fine, Linux does not. See the Firmware/driver based RAID section of http://en.wikipedia.org/wiki/RAID#Firmware.2Fdriver_based_RAID

There are 2 ways to address this issue.

1. Do not use the RAID on the controller, rather let the system detect it as 2 separate disks and use the RAID capabilities of the OS
2. Purchase a true hardware RAID card and put it into the system.

Hope this helps.

Actually this "fake raid" works perfectly fine for me. It writes down the same data on separate disks and reads it as fast as hardware raid. But! Yes, when i take one hdd out whole server stops responding. Its ok with me cose i have kvm switch in dc. Here comes the next question. Whats the easiest way to copy data from one hdd to another, make an absolute mirror copy of data on the hard drive.
Why im asking this is because lets say one hard drive dies. We reboot the server, turn off the onboard fake raid and we have one hard drive running. We put new hard drive into the bay reboot the server turn on the oboard fake raid and it asks to rebuild the whole massive which means loosing of all data. But one hard drive contains data.
Any way to do it from bios?

Thanks.

Instead of turning off the RAID, you should have replaced the drive.

I try replacing it. In console it appears that system trying to recover second hard drive but it says:
scsi 0:0:0:0: rejecting I/O to dead device and stops ..
I did try rebooting the machine and while rebooting it it says multiple times the same this: scsi 0:0:0:0: rejecting I/O to dead device
And after reboot only one hard drive is functioning. Did i miss some set up in Bios?

Thanks

Doesn't your BIOS have a reconstruct option for the RAID?

It has rebuild option in raid set up but if i apply this option it will erase all the data.
But it doesnt seem to have a reconstruct option, but ill keep on looking.

[quote]styx wrote:
It has rebuild option in raid set up but if i apply this option it will erase all the data.[/quote]
Unintuitive. If true, then the nvidia raid depends entirely on the software portion (ie OS driver) for the rebuild. And 'dmraid' in Linux assumes that the firmware does the work.

But "RAID is not a Backup". So you want a backup? Many options. Obviously, you cannot just copy files on live system, as files do change while you copy.

1. Go offline (boot to LiveCD/USB, etc) and 'dd if=/dev/source of=/dev/backup'. Bit hard remotely.

2. Build the system over LVM2. Make a LVM Snapshot, and then copy that. With sufficient space for snapshot, you should be able to finish copy in time.

3. Have the system on software raid (mdadm). 'mdadm' can remove and add disks to mirror and rebuild them online. Essentially same as your fakeraid solution, but we know the tools a bit better.

let it finish mirroring before playing around...make both bootable