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Old 12-10-2007, 11:45 AM
 
Default Raid 1

We put Raid 1 (software) on an IBM server.* I installed some software and made sure everything
worked.* Then we realized we needed to set up grub so the machine would boot from either disk.
So under Linux Rescue we went into grub and did

**** device (hd0)* /dev/sda
**** root (hd0,0)
**** setup (hd0)

**** device (hd1)* /dev/sdb

**** root (hd1,0)

**** setup (hd1)

But then when we booted, everything failed.* I noticed a commone
message "initlog not found" so I looked on another machine and
foiund it under /sbin but not on this one.* So I copied it to /sbin and
rebooted.* It got a lot farther this time, but then got stuck on not being
able to find a default theme.

I also noticed that linux rescue puts the linux under /mnt/sysimage
(so /etc is /mnt/sysimage/etc, /home is /mnt/sysimage/home, etc)
but in addition to those there was still a /etc, /home, etc.* I suppose
one was the mirrored disk.

So it sounds like we might not have done something correctly.* Anyone
have any idea?* We did set up the whole raid system correctly during
Linux installation on a different machine, and then used that anaconda-ks.cfg
file for this one (removing the "#"'s where the raid stuff was commented out
in the config file).

Thanks


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Old 12-10-2007, 02:19 PM
Sean Bruno
 
Default Raid 1

On Mon, 2007-12-10 at 12:45 +0000, tony.chamberlain@lemko.com wrote:
>
>
> We put Raid 1 (software) on an IBM server. I installed some software
> and made sure everything
> worked. Then we realized we needed to set up grub so the machine
> would boot from either disk.
> So under Linux Rescue we went into grub and did
>
> device (hd0) /dev/sda
> root (hd0,0)
> setup (hd0)
>
> device (hd1) /dev/sdb
> root (hd1,0)
> setup (hd1)
>
> But then when we booted, everything failed. I noticed a commone
> message "initlog not found" so I looked on another machine and
> foiund it under /sbin but not on this one. So I copied it to /sbin
> and
> rebooted. It got a lot farther this time, but then got stuck on not
> being
> able to find a default theme.
>
> I also noticed that linux rescue puts the linux under /mnt/sysimage
> (so /etc is /mnt/sysimage/etc, /home is /mnt/sysimage/home, etc)
> but in addition to those there was still a /etc, /home, etc. I
> suppose
> one was the mirrored disk.
>
> So it sounds like we might not have done something correctly. Anyone
> have any idea? We did set up the whole raid system correctly during
> Linux installation on a different machine, and then used that
> anaconda-ks.cfg
> file for this one (removing the "#"'s where the raid stuff was
> commented out
> in the config file).

Can you post the output of "mdadm --detail /dev/mdX" for each raid
device on your machine? It almost sounds like the RAID isn't working
for you.

Sean

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Old 12-10-2007, 05:58 PM
"Jeffrey Ross"
 
Default Raid 1

>
>
> We put Raid 1 (software) on an IBM server. I installed some software and
> made sure everything
> worked. Then we realized we needed to set up grub so the machine would
> boot from either disk.
> So under Linux Rescue we went into grub and did
>
> device (hd0) /dev/sda
> root (hd0,0)
> setup (hd0)
>
> device (hd1) /dev/sdb
> root (hd1,0)
> setup (hd1)
>
> But then when we booted, everything failed. I noticed a commone
> message "initlog not found" so I looked on another machine and
> foiund it under /sbin but not on this one. So I copied it to /sbin and
> rebooted. It got a lot farther this time, but then got stuck on not being
> able to find a default theme.
>
> I also noticed that linux rescue puts the linux under /mnt/sysimage
> (so /etc is /mnt/sysimage/etc, /home is /mnt/sysimage/home, etc)
> but in addition to those there was still a /etc, /home, etc. I suppose
> one was the mirrored disk.
>
> So it sounds like we might not have done something correctly. Anyone
> have any idea? We did set up the whole raid system correctly during
> Linux installation on a different machine, and then used that
> anaconda-ks.cfg
> file for this one (removing the "#"'s where the raid stuff was commented
> out
> in the config file).
>

Tony,

Check out a post I made about 6 months or so ago...
https://www.redhat.com/archives/fedora-list/2007-June/msg06369.html

I converted a system from a non-raid system to a raid1 system

Jeff


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Old 12-12-2007, 11:11 AM
 
Default rAID 1

Here's a question.
If it weren't correct, when you
boot would it stop at the grub prompt?



-----Original Message-----




Message: 3

Date: Tue, 11 Dec 2007 08:05:13 -0800

From: Sean Bruno <sean.bruno@dsl-only.net>

Subject: Re: raid1

To: For users of Fedora <fedora-list@redhat.com>

Message-ID: <1197389113.32026.1.camel@home-desk>

Content-Type: text/plain





On Tue, 2007-12-11 at 12:49 +0000, tony.chamberlain@lemko.com wrote:

> This is of course a more recent installation.

>

> I just found that in /etc/cron.daily there is a file with a script

> (directory name changed for confidentiality)

>

> cd /a/b/c/d

> find . -name '*log*' -exec rm -f {} ;

>

> So if there is no /a/b/c/d it will stay in whatever directory it is in

> (probably root). That is why like initlog, login_pam,so etc.

> have been removed. I just don't know why the stuff in cron.daily

> ran in the afternoon when in /etc/crontabit is set to go at like

> 4:00 AM and this was installed much after 4:00 AM, so the

> cron.daily really shouldn't have run until the next day.

>

>

> Here is the output of the raid commands:

>

> /dev/md0:

> Version : 00.90.01

> Creation Time : Mon Dec 3 11:12:48 2007

> Raid Level : raid1

> Array Size : 104320 (101.89 MiB 106.82 MB)

> Device Size : 104320 (101.89 MiB 106.82 MB)

> Raid Devices : 2

> Total Devices : 2

> Preferred Minor : 0

> Persistence : Superblock is persistent

>

> Update Time : Mon Dec 10 16:30:59 2007

> State : clean

> Active Devices : 2

> Working Devices : 2

> Failed Devices : 0

> Spare Devices : 0

>

> UUID : 45d9ab4a:fc74db66:3a595fea:7e2afbdd

> Events : 0.335920

>

> Number Major Minor RaidDevice State

> 0 8 1 0 active

> sync /dev/sda1

> 1 8 17 1 active

> sync /dev/sdb1

>

>

> /dev/md1:

> Version : 00.90.01

> Creation Time : Mon Dec 10 09:58:53 2007

> Raid Level : raid1

> Array Size : 69537280 (66.32 GiB 71.21 GB)

> Device Size : 69537280 (66.32 GiB 71.21 GB)

> Raid Devices : 2

> Total Devices : 2

> Preferred Minor : 1

> Persistence : Superblock is persistent

>

> Update Time : Tue Dec 11 06:36:51 2007

> State : clean

> Active Devices : 2

> Working Devices : 2

> Failed Devices : 0

> Spare Devices : 0

>

> UUID : c44f476d:a1f38eb3:b74e1d2d:66efa904

> Events : 0.21479

>

> Number Major Minor RaidDevice State

> 0 8 2 0 active

> sync /dev/sda2

> 1 8 18 1 active

> sync /dev/sdb2

>

>

>

>

>

>

> ------------------------------

>

> Message: 5

> Date: Mon, 10 Dec 2007 07:19:55 -0800

> From: Sean Bruno <sean.bruno@dsl-only.net>

> Subject: Re: Raid 1

> To: For users of Fedora <fedora-list@redhat.com>

> Message-ID: <1197299995.25236.3.camel@home-desk>

> Content-Type: text/plain

>

>

> On Mon, 2007-12-10 at 12:45 +0000, tony.chamberlain@lemko.com wrote:

> >

> >

> > We put Raid 1 (software) on an IBM server. I installed some software

> > and made sure everything

> > worked. Then we realized we needed to set up grub so the machine

> > would boot from either disk.

> > So under Linux Rescue we went into grub and did

> >

> > device (hd0) /dev/sda

> > root (hd0,0)

> > setup (hd0)

> >

> > device (hd1) /dev/sdb

> > root (hd1,0)

> > setup (hd1)

> >

> > But then when we booted, everything failed. I noticed a commone

> > message "initlog not found" so I looked on another machine and

> > foiund it under /sbin but not on this one. So I copied it to /sbin

> > and

> > rebooted. It got a lot farther this time, but then got stuck on not

> > being

> > able to find a default theme.

> >

> > I also noticed that linux rescue puts the linux under /mnt/sysimage

> > (so /etc is /mnt/sysimage/etc, /home is /mnt/sysimage/home, etc)

> > but in addition to those there was still a /etc, /home, etc. I

> > suppose

> > one was the mirrored disk.

> >

> > So it sounds like we might not have done something correctly. Anyone

> > have any idea? We did set up the whole raid system correctly during

> > Linux installation on a different machine, and then used that

> > anaconda-ks.cfg

> > file for this one (removing the "#"'s where the raid stuff was

> > commented out

> > in the config file).

>

> Can you post the output of "mdadm --detail /dev/mdX" for each raid

> device on your machine? It almost sounds like the RAID isn't working

> for you.

>

> Sean



So, does your system boot at all? Or does it fail when you try to boot

off of one drive vs. another?



Sean







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Old 12-12-2007, 08:41 PM
"Erik P. Olsen"
 
Default rAID 1

Please keep the original thread instead of creating new threads for the same issue.

--
Erik.

tony.chamberlain@lemko.com wrote:

Here's a question.
If it weren't correct, when you
boot would it stop at the grub prompt?

-----Original Message-----


Message: 3
Date: Tue, 11 Dec 2007 08:05:13 -0800
From: Sean Bruno <sean.bruno@dsl-only.net>
Subject: Re: raid1
To: For users of Fedora <fedora-list@redhat.com>
Message-ID: <1197389113.32026.1.camel@home-desk>
Content-Type: text/plain


On Tue, 2007-12-11 at 12:49 +0000, tony.chamberlain@lemko.com wrote:
> This is of course a more recent installation.
>
> I just found that in /etc/cron.daily there is a file with a script
> (directory name changed for confidentiality)
>
> cd /a/b/c/d
> find . -name '*log*' -exec rm -f {} ;
>
> So if there is no /a/b/c/d it will stay in whatever directory it is in
> (probably root). That is why like initlog, login_pam,so etc.
> have been removed. I just don't know why the stuff in cron.daily
> ran in the afternoon when in /etc/crontabit is set to go at like
> 4:00 AM and this was installed much after 4:00 AM, so the
> cron.daily really shouldn't have run until the next day.
>
>
> Here is the output of the raid commands:
>
> /dev/md0:
> Version : 00.90.01
> Creation Time : Mon Dec 3 11:12:48 2007
> Raid Level : raid1
> Array Size : 104320 (101.89 MiB 106.82 MB)
> Device Size : 104320 (101.89 MiB 106.82 MB)
> Raid Devices : 2
> Total Devices : 2
> Preferred Minor : 0
> Persistence : Superblock is persistent
>
> Update Time : Mon Dec 10 16:30:59 2007
> State : clean
> Active Devices : 2
> Working Devices : 2
> Failed Devices : 0
> Spare Devices : 0
>
> UUID : 45d9ab4a:fc74db66:3a595fea:7e2afbdd
> Events : 0.335920
>
> Number Major Minor RaidDevice State
> 0 8 1 0 active
> sync /dev/sda1
> 1 8 17 1 active
> sync /dev/sdb1
>
>
> /dev/md1:
> Version : 00.90.01
> Creation Time : Mon Dec 10 09:58:53 2007
> Raid Level : raid1
> Array Size : 69537280 (66.32 GiB 71.21 GB)
> Device Size : 69537280 (66.32 GiB 71.21 GB)
> Raid Devices : 2
> Total Devices : 2
> Preferred Minor : 1
> Persistence : Superblock is persistent
>
> Update Time : Tue Dec 11 06:36:51 2007
> State : clean
> Active Devices : 2
> Working Devices : 2
> Failed Devices : 0
> Spare Devices : 0
>
> UUID : c44f476d:a1f38eb3:b74e1d2d:66efa904
> Events : 0.21479
>
> Number Major Minor RaidDevice State
> 0 8 2 0 active
> sync /dev/sda2
> 1 8 18 1 active
> sync /dev/sdb2
>
>
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Mon, 10 Dec 2007 07:19:55 -0800
> From: Sean Bruno <sean.bruno@dsl-only.net>
> Subject: Re: Raid 1
> To: For users of Fedora <fedora-list@redhat.com>
> Message-ID: <1197299995.25236.3.camel@home-desk>
> Content-Type: text/plain
>
>
> On Mon, 2007-12-10 at 12:45 +0000, tony.chamberlain@lemko.com wrote:
> >
> >
> > We put Raid 1 (software) on an IBM server. I installed some software
> > and made sure everything
> > worked. Then we realized we needed to set up grub so the machine
> > would boot from either disk.
> > So under Linux Rescue we went into grub and did
> >
> > device (hd0) /dev/sda
> > root (hd0,0)
> > setup (hd0)
> >
> > device (hd1) /dev/sdb
> > root (hd1,0)
> > setup (hd1)
> >
> > But then when we booted, everything failed. I noticed a commone
> > message "initlog not found" so I looked on another machine and
> > foiund it under /sbin but not on this one. So I copied it to /sbin
> > and
> > rebooted. It got a lot farther this time, but then got stuck on not
> > being
> > able to find a default theme.
> >
> > I also noticed that linux rescue puts the linux under /mnt/sysimage
> > (so /etc is /mnt/sysimage/etc, /home is /mnt/sysimage/home, etc)
> > but in addition to those there was still a /etc, /home, etc. I
> > suppose
> > one was the mirrored disk.
> >
> > So it sounds like we might not have done something correctly. Anyone
> > have any idea? We did set up the whole raid system correctly during
> > Linux installation on a different machine, and then used that
> > anaconda-ks.cfg
> > file for this one (removing the "#"'s where the raid stuff was
> > commented out
> > in the config file).
>
> Can you post the output of "mdadm --detail /dev/mdX" for each raid
> device on your machine? It almost sounds like the RAID isn't working
> for you.
>
> Sean

So, does your system boot at all? Or does it fail when you try to boot
off of one drive vs. another?

Sean



-



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Old 04-03-2008, 09:35 PM
Karl Larsen
 
Default Raid 1

I put things in google and it found:

http://mywheel.net/blog/index.php/software-raid-in-ubuntu/

and I copied the words to my computer for study. It is like this:



This is a small tutorial to help you getting started with Software RAID
in Ubuntu. It was tested on Ubuntu Server 6.06 but it will probably work
on Breezy or even on Debian.

Actually, it could possibly work in any GNU/Linux flavour around but I
won?t guarantee on that :-)

Please take in attention that you can loose your data! If it happens,
don?t complain to me. Follow these guidelines on your own risk.

Why I became paranoid

Five years ago I lost an IBM 80G hard drive that was full of photos,
past works and several other important stuff that really mattered to me.
I almost cried.

Since then, I became a paranoid with keeping my data safe from harm. I
have several machines and there?s a lot of files spawned among them.
Call it ?Distributed backuping?. Unfortunately, it?s not very useful so
I decided I had to have a system that was yet easily usable.

RAID 1 was the answer.

What I bought

To accomplish such, I bought 2x Seagate Barracuda 7200RPM 160GB 8MB
Cache. Seagate is well known for is fiability so I didn?t consider any
other branch.

Software RAID vs Hardware RAID

Hardware RAID is a must for servers who have a high demand and need
serious throughput. Not the case of my home server that?s acting as a
fileserver!

Plus, I didn?t have any RAID controller around and sparing ?140 on the
hard drivers was enough for one day.

I won?t stand my claims (that Software RAID works great for a home
server) since you can do it for yourself. Adaptec has some really nice
research papers that should how good software RAID can be ? although
stating that their hardware RAID is better ;-)

Setting up the hardware

I don?t know in depth how the IDE controller works so I couldn?t
conclude for myself (nor I had the time to investigate it any further
:-) if setting up both hard drives on the same IDE connector (1x Master,
1x Slave) would be faster than having separate IDE connectors (1x
Master, 1x Mater). I picked the latter. I?ll wait for some insightful
response to this question.

Update

Here?s the response, from Carlos Rodrigues. Thanks Carlos :-)

An IDE channel is a shared bus, so only one drive may be
pumping/receiving data at any given time, and some commands lock the bus
(try having a CD-Writer and a CD reader on the same channel, and opening
and closing the tray on the reader while the writer is recording?
instant buffer underrun). Plus, changing directions (write a ?read??
command/read data/write a ?write?? command/?) is expensive over IDE, so
software RAID on a single IDE channel is very bad performance-wise.

On the mean time, you can proceed with any of the approaches and revert
it later.

Setting it all from the command line

The system was all set up prior to the Software RAID. Also, I don?t have
any X server so all I did was through the command line. Actually,
through an SSH session.

The hard work

The first thing I did was checking if both hard drives were being
correctly detected on BIOS. They were, let?s move on.

Next, let?s set a partition on each disk and then set its type to Linux
RAID. To do such, let?s first figure out which devices the disks got
mapped to.

Type $ cat /proc/diskstats. Mine were detected as /dev/hda and /dev/hdc.

To set up a partitition, run fdisk twice, each one for each disk and do
the following:

$ fdisk /dev/hdX

Type ?n?, create a logic partition. Write down the cylinders you used
because the partitions on the others disk have to fill the same exact
ammount of space. Set it?s type to ?fd? by typing t. Finally, save the
changes by typing w.

I?ll remember once again than you have to follow this procedure twice,
once of earch hard drive.

Now it?s time to create the virtual disk. Make sure mdadm is installed.
If it isn?t, I can lend you a hand on that. Just do

$ apt-get install mdadm

Then, fire up the following command

$ mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/hda1
/dev/hdc1

Congratulations, your virtual RAID1 hard drive has been successfully
created!

Now we need to create a partition with a real file system instead of
that virtual Linux RAID you set before.

We?re almost done. Restart the computer.

$ shutdown -r now

The disks are now being synced. You can?t use the virtual disk.. yet. Type

$ watch cat /proc/mdstat and wait until the rsync finishes. In the
meanwhile, get a nice cup of coffee of your favourite beverage.

Did it finish? Great!

Format it:

$ mkfs -t reiserfs /dev/md0

Add the new virtual disk entry to /etc/fstab (explaining how /etc/fstab
works is out of the scope of this article) and do issue

$ mount -a

Conclusions

You just set a Software RAID on GNU/Linux through the command line.
Bottom line conclusions: Linux rocks! :-)

References

http://www.linuxdevcenter.com/pub/a/linux/2002/12/05/RAID.html

https://wiki.ubuntu.com/Raid?highlight=%28raid%29

http://www.howtoforge.com/linux_software_raid

Future work

There?s still a question to be answered. I also welcome any comments
correcting grammar, syntax or any other kind of errors.


This gets you well on the way to Software Raid 1 and it should work. I
got mdadm with no problems. When time permits I will try and get it set
up with one HD an IDE and the other a SATA. Not sure how this will work
but will find out by doing it :-)

Karl

--

Karl F. Larsen, AKA K5DI
Linux User
#450462 http://counter.li.org.
PGP 4208 4D6E 595F 22B9 FF1C ECB6 4A3C 2C54 FE23 53A7


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Old 04-04-2008, 01:00 PM
Gerald Dachs
 
Default Raid 1

Quoting Karl Larsen <k5di@zianet.com>:

> Since then, I became a paranoid with keeping my data safe from harm. I
> have several machines and there?s a lot of files spawned among them.
> Call it ?Distributed backuping?. Unfortunately, it?s not very useful so
> I decided I had to have a system that was yet easily usable.
>
> RAID 1 was the answer.

Just to make something clear: RAID 1 is no replacement for a working
backup strategy! In real life most of us loose data much more often
because we deleted
the wrong file, or some of our programms behave ugly instead of a
broken harddisk. The files will be deleted, or destroyed on all disks
of the raid in milliseconds.

You have to have a working backup strategy first if you are really paranoid.
After this you can follow Karls advice, but you don't have to, if you can live
with the loose of one days work.

Gerald

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Old 04-04-2008, 03:23 PM
Victor Sterpu
 
Default Raid 1

Thank you for the docs.
I was doing the raid 1 ok.
As Markus said Ubuntu has a problem with raid 1.
This bug was the problem https://bugs.launchpad.net/ubuntu/+bug/133663.
Maybe it will be fixed in Ubuntu version 8.

Karl Larsen wrote:
> I put things in google and it found:
>
> http://mywheel.net/blog/index.php/software-raid-in-ubuntu/
>
> and I copied the words to my computer for study. It is like this:
>
>
>
> This is a small tutorial to help you getting started with Software RAID
> in Ubuntu. It was tested on Ubuntu Server 6.06 but it will probably work
> on Breezy or even on Debian.
>
> Actually, it could possibly work in any GNU/Linux flavour around but I
> won’t guarantee on that :-)
>
> Please take in attention that you can loose your data! If it happens,
> don’t complain to me. Follow these guidelines on your own risk.
>
> Why I became paranoid
>
> Five years ago I lost an IBM 80G hard drive that was full of photos,
> past works and several other important stuff that really mattered to me.
> I almost cried.
>
> Since then, I became a paranoid with keeping my data safe from harm. I
> have several machines and there’s a lot of files spawned among them.
> Call it “Distributed backuping”. Unfortunately, it’s not very useful so
> I decided I had to have a system that was yet easily usable.
>
> RAID 1 was the answer.
>
> What I bought
>
> To accomplish such, I bought 2x Seagate Barracuda 7200RPM 160GB 8MB
> Cache. Seagate is well known for is fiability so I didn’t consider any
> other branch.
>
> Software RAID vs Hardware RAID
>
> Hardware RAID is a must for servers who have a high demand and need
> serious throughput. Not the case of my home server that’s acting as a
> fileserver!
>
> Plus, I didn’t have any RAID controller around and sparing €140 on the
> hard drivers was enough for one day.
>
> I won’t stand my claims (that Software RAID works great for a home
> server) since you can do it for yourself. Adaptec has some really nice
> research papers that should how good software RAID can be — although
> stating that their hardware RAID is better ;-)
>
> Setting up the hardware
>
> I don’t know in depth how the IDE controller works so I couldn’t
> conclude for myself (nor I had the time to investigate it any further
> :-) if setting up both hard drives on the same IDE connector (1x Master,
> 1x Slave) would be faster than having separate IDE connectors (1x
> Master, 1x Mater). I picked the latter. I’ll wait for some insightful
> response to this question.
>
> Update
>
> Here’s the response, from Carlos Rodrigues. Thanks Carlos :-)
>
> An IDE channel is a shared bus, so only one drive may be
> pumping/receiving data at any given time, and some commands lock the bus
> (try having a CD-Writer and a CD reader on the same channel, and opening
> and closing the tray on the reader while the writer is recording…
> instant buffer underrun). Plus, changing directions (write a “read??
> command/read data/write a “write?? command/…) is expensive over IDE, so
> software RAID on a single IDE channel is very bad performance-wise.
>
> On the mean time, you can proceed with any of the approaches and revert
> it later.
>
> Setting it all from the command line
>
> The system was all set up prior to the Software RAID. Also, I don’t have
> any X server so all I did was through the command line. Actually,
> through an SSH session.
>
> The hard work
>
> The first thing I did was checking if both hard drives were being
> correctly detected on BIOS. They were, let’s move on.
>
> Next, let’s set a partition on each disk and then set its type to Linux
> RAID. To do such, let’s first figure out which devices the disks got
> mapped to.
>
> Type $ cat /proc/diskstats. Mine were detected as /dev/hda and /dev/hdc.
>
> To set up a partitition, run fdisk twice, each one for each disk and do
> the following:
>
> $ fdisk /dev/hdX
>
> Type ‘n’, create a logic partition. Write down the cylinders you used
> because the partitions on the others disk have to fill the same exact
> ammount of space. Set it’s type to ‘fd’ by typing t. Finally, save the
> changes by typing w.
>
> I’ll remember once again than you have to follow this procedure twice,
> once of earch hard drive.
>
> Now it’s time to create the virtual disk. Make sure mdadm is installed.
> If it isn’t, I can lend you a hand on that. Just do
>
> $ apt-get install mdadm
>
> Then, fire up the following command
>
> $ mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/hda1
> /dev/hdc1
>
> Congratulations, your virtual RAID1 hard drive has been successfully
> created!
>
> Now we need to create a partition with a real file system instead of
> that virtual Linux RAID you set before.
>
> We’re almost done. Restart the computer.
>
> $ shutdown -r now
>
> The disks are now being synced. You can’t use the virtual disk.. yet. Type
>
> $ watch cat /proc/mdstat and wait until the rsync finishes. In the
> meanwhile, get a nice cup of coffee of your favourite beverage.
>
> Did it finish? Great!
>
> Format it:
>
> $ mkfs -t reiserfs /dev/md0
>
> Add the new virtual disk entry to /etc/fstab (explaining how /etc/fstab
> works is out of the scope of this article) and do issue
>
> $ mount -a
>
> Conclusions
>
> You just set a Software RAID on GNU/Linux through the command line.
> Bottom line conclusions: Linux rocks! :-)
>
> References
>
> http://www.linuxdevcenter.com/pub/a/linux/2002/12/05/RAID.html
>
> https://wiki.ubuntu.com/Raid?highlight=%28raid%29
>
> http://www.howtoforge.com/linux_software_raid
>
> Future work
>
> There’s still a question to be answered. I also welcome any comments
> correcting grammar, syntax or any other kind of errors.
>
>
> This gets you well on the way to Software Raid 1 and it should work. I
> got mdadm with no problems. When time permits I will try and get it set
> up with one HD an IDE and the other a SATA. Not sure how this will work
> but will find out by doing it :-)
>
> Karl
>
>


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Old 04-10-2008, 06:25 PM
Dan Farrell
 
Default Raid 1

On Thu, 03 Apr 2008 15:35:03 -0600
Karl Larsen <k5di@zianet.com> wrote:

> I don't know in depth how the IDE controller works so I couldn't
> conclude for myself (nor I had the time to investigate it any further
> :-) if setting up both hard drives on the same IDE connector (1x
> Master, 1x Slave) would be faster than having separate IDE connectors
> (1x Master, 1x Mater). I picked the latter. I'll wait for some
> insightful response to this question.

It is my understanding that putting two drives on the same ide channel
(1 master, 1 slave) is a poor idea in general, and leads to really
crummy performance if you RAID them together.

Most IDE Controllers have two channels, each of which has its own cable
and can support up to 2 drives. However, each channel can only get the
most out of 1 drive.

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Old 04-10-2008, 07:13 PM
Jonathan Hirschman
 
Default Raid 1

Dan Farrell wrote:
> On Thu, 03 Apr 2008 15:35:03 -0600
> Karl Larsen <k5di@zianet.com> wrote:
>
>
>> I don't know in depth how the IDE controller works so I couldn't
>> conclude for myself (nor I had the time to investigate it any further
>> :-) if setting up both hard drives on the same IDE connector (1x
>> Master, 1x Slave) would be faster than having separate IDE connectors
>> (1x Master, 1x Mater). I picked the latter. I'll wait for some
>> insightful response to this question.
>>
>
> It is my understanding that putting two drives on the same ide channel
> (1 master, 1 slave) is a poor idea in general, and leads to really
> crummy performance if you RAID them together.
>
> Most IDE Controllers have two channels, each of which has its own cable
> and can support up to 2 drives. However, each channel can only get the
> most out of 1 drive.
This is correct. PATA, the old style IDE with ribbon cables, is limited
to one command at a time, and only one device can have access to the IDE
bus at a time. There are some exceptions, but for the most part, this
rule of thumb holds true.

Given that, a mirror would mean that two drives would alternate reads
and writes (and I believe that md gives you "split reads" if you do a
RAID 1 - meaning that you can do two seeks in parallel as opposed to
single drive). If you put the drives on two separate IDE channels,
writes can happen in parallel, and you should see read performance
become substantially faster (as you can now have two separate reads at a
time, as opposed to one at a time with a single drive).

Clear as mud?

jh

jh

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