I'm looking into RAID, and as such I started to read the suse manual and the raid howto on the web. I still have some questions that someone on this list can answer. 1) Is it possible to add a soft raid after installation? The system I want to extend with raid (raid 1) is already up and running on single disk system (it has 2 disks). 2) How does one enable hardware raid. The motherboard has an onboard hardware raid controller. The controller does not really seem to be supported by linux (Promise 378). Anyway, I ask this out of interest ;) In case of hardware should it be done via the bios or completely different? -- Richard Bos Without a home the journey is endless
On Mon, 2005-02-28 at 06:06, Richard Bos wrote:
I'm looking into RAID, and as such I started to read the suse manual and the raid howto on the web. I still have some questions that someone on this list can answer.
1) Is it possible to add a soft raid after installation? The system I want to extend with raid (raid 1) is already up and running on single disk system (it has 2 disks).
Cannot help with this one.
2) How does one enable hardware raid. The motherboard has an onboard hardware raid controller. The controller does not really seem to be supported by linux (Promise 378). Anyway, I ask this out of interest ;) In case of hardware should it be done via the bios or completely different?
Since the controller is not supported it really is not an issue with this MB. If you purchase another controller make sure it has true hardware raid onboard and does not use software to do the work otherwise you would be just as well off using software raid. If you find a driver for this controller and want to use the current install drive, make sure you backup all of your work as adding this drive to the raid set will destroy any data on the disk. -- Ken Schneider UNIX since 1989, linux since 1994, SuSE since 1998 * Only reply to the list please* "The day Microsoft makes something that doesn't suck is probably the day they start making vacuum cleaners." -Ernst Jan Plugge
On Mon, 28 Feb 2005 12:06:23 +0100, Richard Bos
I'm looking into RAID, and as such I started to read the suse manual and the raid howto on the web. I still have some questions that someone on this list can answer.
1) Is it possible to add a soft raid after installation? The system I want to extend with raid (raid 1) is already up and running on single disk system (it has 2 disks).
Don't know.
2) How does one enable hardware raid. The motherboard has an onboard hardware raid controller. The controller does not really seem to be supported by linux (Promise 378). Anyway, I ask this out of interest ;) In case of hardware should it be done via the bios or completely different?
Typically hardware raid has the initial setup performed at the BIOS level. Ongoing maintenance etc. is typically handled by the OS (kernel driver + userspace). For instance, to create a RAID 5 set you typically have to access the bios. Then later if you have a disk failure and you need to swap it out, the notification and swap-out management have to be handled without having to reboot the server, thus the driver / user space apps have to manage this process. Greg -- Greg Freemyer
On Monday 28 February 2005 02:06 am, Richard Bos wrote:
I'm looking into RAID, and as such I started to read the suse manual and the raid howto on the web. I still have some questions that someone on this list can answer.
1) Is it possible to add a soft raid after installation? The system I want to extend with raid (raid 1) is already up and running on single disk system (it has 2 disks).
Yes. But... I would recommend you avoid putting your boot device on a software raid for your first go-around. It can be done, but it requires more learning. Most raids I setup are software raids, and the root drive (with boot partition and linux software) are all non-raided, as is swap. All mission data files, is on the raid. I have a batch job copy certain files from /etc to a backup location on the raid nightly. That way, I can upgrade the OS, without having to involve the raid. Yes, my OS drive is not protected, but it is fairly easy to rebuild, and I keep copies of critical files. Converting a single partition to raid after the fact is fairly easy, sort of like what happens should one raid drive fail. Put both partitions in the raid (man mdadm ) but put the empty drive in as a spare. As soon as the raid fires up it will replicate the data from the live drive to the empty.
2) How does one enable hardware raid. The motherboard has an onboard hardware raid controller. The controller does not really seem to be supported by linux (Promise 378). Anyway, I ask this out of interest ;) In case of hardware should it be done via the bios or completely different?
If drivers are not present in your distro, I would consider software raid instead. Hardware raid always has to fight the driver wars, and it never gets any better than the day it was first installed. Software raid benefits from every processor/memory upgrade along the way, and gets better. Some raid controllers can be jumper-ed to be regular dual channel ide controllers. That's the way I've been using mine. -- _____________________________________ John Andersen
Op dinsdag 1 maart 2005 04:02, schreef John Andersen:
Converting a single partition to raid after the fact is fairly easy, sort of like what happens should one raid drive fail. Put both partitions in the raid (man mdadm ) but put the empty drive in as a spare. As soon as the raid fires up it will replicate the data from the live drive to the empty.
John, thanks for your info on RAID. I have the following partitions: /home /opt /usr /tmp /var /swap / To add them to a RAID, I do the following (I assume here): On the other disk I create the same sized partitions for /home /opt /usr /var Add them to the raid with mdadm, restart the raid and that's all? What's the problem to add "/" to the raid? I ask because what I would like to have is the following; if e.g. the main disk fails, I boot from the other one, which should be possible as all data has been mirrored. But that's only a valid statement in case "/" is on the raid as well... -- Richard Bos Without a home the journey is endless
On Tuesday 01 March 2005 11:10 am, Richard Bos wrote:
What's the problem to add "/" to the raid? I ask because what I would like to have is the following; if e.g. the main disk fails, I boot from the other one, which should be possible as all data has been mirrored. But that's only a valid statement in case "/" is on the raid as well...
I forget the details right now, but I believe it was something about having to place raid modules in your initrd or boot image so that the loader (grub) can get these modules loaded at boot time in order to boot from the raid. It was not an insurmountable problem and I find the docs to do it somewhere on the web with google. Got them stored somewhere at work, but not here. -- _____________________________________ John Andersen
The Monday 2005-02-28 at 18:02 -0900, John Andersen wrote:
Most raids I setup are software raids, and the root drive (with boot partition and linux software) are all non-raided, as is swap. All mission data files, is on the raid. I have a batch job copy certain files from /etc to a backup location on the raid nightly.
That way, I can upgrade the OS, without having to involve the raid. Yes, my OS drive is not protected, but it is fairly easy to rebuild, and I keep copies of critical files.
You may have / and /boot (if diferent) replicated on the other(s) disk, so that you can boot from the spare if needed. ...
If drivers are not present in your distro, I would consider software raid instead. Hardware raid always has to fight the driver wars, and it never gets any better than the day it was first installed. Software raid benefits from every processor/memory upgrade along the way, and gets better.
Some raid controllers can be jumper-ed to be regular dual channel ide controllers. That's the way I've been using mine.
It was said by somebody who knew, some time ago in this list, that so called hardware raid, on the motherboard, were not really hardware raid. I don't have the reference handy, though. -- Cheers, Carlos Robinson
On Monday 28 February 2005 13:06, Richard Bos wrote:
2) How does one enable hardware raid. The motherboard has an onboard hardware raid controller. The controller does not really seem to be supported by linux (Promise 378). Anyway, I ask this out of interest ;) In case of hardware should it be done via the bios or completely different?
That's called fakeraid, because it's not true hardware raid. You're better off with linux' software raid, if you don't dual boot with windows. http://www.linuxmafia.com/faq/Hardware/sata.html
Op woensdag 2 maart 2005 14:53, schreef Silviu Marin-Caea:
That's called fakeraid, because it's not true hardware raid. You're better off with linux' software raid, if you don't dual boot with windows.
Nice to know. -- Richard Bos Without a home the journey is endless
On Mon, 2005-02-28 at 06:06, Richard Bos wrote:
I'm looking into RAID, and as such I started to read the suse manual and the raid howto on the web. I still have some questions that someone on this list can answer.
1) Is it possible to add a soft raid after installation? The system I want to extend with raid (raid 1) is already up and running on single disk system (it has 2 disks).
I have done this many times and have posted some instructions to this list. I'm not at home right now, but basically: Install your new disk and reboot. Use fdisk to partition the new disk just like the old disk I create "broken" raid device(s) from hdb with an /etc/raidtab like this: raiddev /dev/md0 raid-level 1 nr-raid-disks 2 nr-spare-disks 0 persistent-superblock 1 device /dev/hda1 failed-disk 0 device /dev/hdb1 raid-disk 1 Add more sections to the file for each partition you want to mirror. Then mkraid /dev/md0 (and any others) and format them. Mount the new device(s) somewhere and copy to them using "cp -a". Don't copy /proc or the mount point for the new raid device. Just create the directories. Modify fstab *on the new raid device*. Create an entry in grub on *both* devices to boot it. If everything boots OK use raidhotadd to to make hda2 part of the raid system (this is the point of no return). Then use grub: grub Grub>device (hd0) /dev/hda Grub>root (hd0,0) and then: Grub>setup (hd0) Grub>device (hd0) /dev/hdb Grub>root (hd0,0) and then: Grub>setup (hd0) quit This has worked for me on several machines. I hope it helps you out. Louis Richards
participants (7)
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Carlos E. R. -
Greg Freemyer -
John Andersen -
Ken Schneider -
Louis Richards -
Richard Bos -
Silviu Marin-Caea