Just trying to plan a move to RAID 5 and LVs and came across a small bit of
information I'd like to verify.

I've read on a document, (http://www.gagme.com/greg/linux/raid-lvm.php) last
edited on Nov 5, that the /boot partition cannot be put on a RAID 5 array
(only RAID 1). Is this true?

I want to replace my 320g + 400g+ 500g +500g system with a 500g +500g +500g
RAID 5 array, put into a growable LV. (There is a separate drive for
backups).

Does this mean that I need a fourth drive outside of the RAID 5 array to
hold /boot ?

....and, since I'm already posting a question, I'm still not sure what
advantages a logical volume will have on my RAID 5 array. RAID 5 can have
drives added to increase the available usable space. Any growable filesystem
that I put on an LV should be able to grow on the RAID 5 without using a LV,
since the RAID 5 is going to appear as a single 1000g physical drive.

Noozer wrote:
> Just trying to plan a move to RAID 5 and LVs and came across a small bit of
> information I'd like to verify.
>
> I've read on a document, (http://www.gagme.com/greg/linux/raid-lvm.php) last
> edited on Nov 5, that the /boot partition cannot be put on a RAID 5 array
> (only RAID 1). Is this true?

As long as you don't have a hardware that takes care of all RAID stuff, you
won't be able to use RAID/LVM for /boot, but then /boot is at most 100MB
(enough for at least 30 kernels), so leaving this outside RAID/LVM will not
cause you any troubles.



--

//Aho

"J.O. Aho" <user@example.net> wrote in message
news:5poq3eFs5keaU1@mid.individual.net...
> Noozer wrote:
>> Just trying to plan a move to RAID 5 and LVs and came across a small bit
>> of
>> information I'd like to verify.
>>
>> I've read on a document, (http://www.gagme.com/greg/linux/raid-lvm.php)
>> last
>> edited on Nov 5, that the /boot partition cannot be put on a RAID 5 array
>> (only RAID 1). Is this true?
>
> As long as you don't have a hardware that takes care of all RAID stuff,
> you
> won't be able to use RAID/LVM for /boot, but then /boot is at most 100MB
> (enough for at least 30 kernels), so leaving this outside RAID/LVM will
> not
> cause you any troubles.

With RAID 5, isn't the whole drive merged into the array?

Reading a bit further I find references to combining partitions into a RAID
5 array. If this were the case I could just create a small partition on one
500g drive and use the rest of the drive as part of the RAID 5 array (which
would just waste a little space on the other drives).

Finally, I think I understand how a LV helps... I can add storage space to
the LV without needing to add it to the RAID 5 array. But wouldn't this
result in an unprotected file system again? (unless I added another RAID
array)

"Noozer" <dont.spam@me.here> wrote in message
news:0yGZi.200804$th2.134976@pd7urf3no...

> Finally, I think I understand how a LV helps... I can add storage space to
> the LV without needing to add it to the RAID 5 array. But wouldn't this
> result in an unprotected file system again? (unless I added another RAID
> array)

*CLICK*

Meaning I can add a RAID 5 array of multiple 750 gig drives later on without
needing to sacrifice my 500g based array.

Hrm... Now I have to figure out how I should migrate my existing system to a
RAID5 & LV based system.

Noozer wrote:

> Finally, I think I understand how a LV helps... I can add storage space to
> the LV without needing to add it to the RAID 5 array. But wouldn't this
> result in an unprotected file system again? (unless I added another RAID
> array)

As last time talking about LVM and RAID, everything depends on how you set up
your system, don't forget that LVM has built in support for mirroring.

--

//Aho

Noozer wrote:

> Just trying to plan a move to RAID 5 and LVs and came across a small bit
> of information I'd like to verify.
>
> I've read on a document, (http://www.gagme.com/greg/linux/raid-lvm.php)
> last edited on Nov 5, that the /boot partition cannot be put on a RAID 5
> array (only RAID 1). Is this true?
>
Yes, at boot time the bios (1st stage boot) doesn't know how to address
raid5. Except you have a hardware raid.

> I want to replace my 320g + 400g+ 500g +500g system with a 500g +500g
> +500g RAID 5 array, put into a growable LV. (There is a separate drive for
> backups).
>
> Does this mean that I need a fourth drive outside of the RAID 5 array to
> hold /boot ?
>
No. You can sacrifice 64M at the beginning, for a /boot partition. Make that
raid1 (you even have one spare), apply the "raid-extra-boot" line to lilo
and make the remainder raid5.

> ...and, since I'm already posting a question, I'm still not sure what
> advantages a logical volume will have on my RAID 5 array. RAID 5 can have
> drives added to increase the available usable space. Any growable
> filesystem that I put on an LV should be able to grow on the RAID 5
> without using a LV, since the RAID 5 is going to appear as a single 1000g
> physical drive.

With new kernels, you can add another 500G drive and extend the array. So if
you have 4x500, you'll be able to use 1500G. That can be done without LVM.
I would not use LVM _together_ with raid, as it can make things rather
confusing.
--
vista policy violation: Microsoft optical mouse found penguin patterns
on mousepad. Partition scan in progress to remove offending
incompatible products. Reactivate MS software.
Linux 2.6.22.9-1mdvcustom [LinuxCounter#295241,ICQ#4918962]

>> Finally, I think I understand how a LV helps... I can add storage space
>> to the LV without needing to add it to the RAID 5 array. But wouldn't
>> this result in an unprotected file system again? (unless I added another
>> RAID array)
>
> *CLICK*
>
> Meaning I can add a RAID 5 array of multiple 750 gig drives later on
> without needing to sacrifice my 500g based array.
>
> Hrm... Now I have to figure out how I should migrate my existing system to
> a RAID5 & LV based system.

I hate computers...

I figured, since my three 500gig drives were now empty, that I would simply
remove my current 320gig and 400gig drives from the system and install only
my 500gig drives. Then I'd simply do a fresh installation of Debian and
finally move any data from my 320 and 400gig drives that I need. This keeps
all my data on the 320 and 400gig drive safe for the process and should
result in predictable drive assignments.

Man was I wrong!!!

One drive is a PATA alone as master on the primary IDE controller. The other
two are SATA on the Intel ICH5 SATA controller. Currently there are no
drives on the Promise SATA controller (but I do plan on adding another 500g
here eventually).

I booted the Debian lenny installation disk, got to the point where I'm
manually partitioning the drives. It's a simple setup.

hda1 - 500meg swap
hda2 - remainder of hda as RAID5
sda1 - 400meg swap
sda2 - 100meg RAID1
sda3 - remainder of sda as RAID5
sdb1 - 400meg swap
sdb2 - 100meg RAID1
sdb3 - remainder of sdb as RAID5

Looks fine, right?

Well, I created the RAID1 partition. No problems. Formatted it as ext3 and
to be mounted ro as /boot.
Now, I go to create the RAID5 partition (which will eventually hold a LV and
my / partition). I choose create, 3 partitions with 0 spares. Then I get the
list of available partitions... sda2, sda3 and sdb3. WHAT??? sda2 is already
allocated to my RAID1! Where's hda2? I cancel the creation. The partition
display looks normal at this point.

Cursing ensues and I choose to delete a RAID partition. I'm given my list of
RAID partitions, expecting to only see /md0, but NOOOoooo... I've got a list
of five choices and none of them will do anything when I choose to delete
them. Unfortunatly I didn't write the choices down, but they were similar
to:

/hda0
:
/md0
d0

I've booted the Seagate diagnostics and zero'd all three drives. I go
through the process again and the exact same thing happens. Needless to say,
I'm not impressed.

I'm using lenny because etch doesn't properly support the use of the Intel
PATA controller, Intel ICH5 SATA controller and the Promise SATA controller
all at the same time.

Does any of this sound familiar? Any idea what is happening?

At this point I'm strongly considering just using another distro, but I
really liked Debian. I've already got Fedora 8 downloaded. I've tried to
install it, but I don't see any method of creating a logical volume during
the install - meaning that I can't put / onto a LV.

On Nov 13, 2:04 pm, "Noozer" <dont.s...@me.here> wrote:
> >> Finally, I think I understand how a LV helps... I can add storage space
> >> to the LV without needing to add it to the RAID 5 array. But wouldn't
> >> this result in an unprotected file system again? (unless I added another
> >> RAID array)
>
> > *CLICK*
>
> > Meaning I can add a RAID 5 array of multiple 750 gig drives later on
> > without needing to sacrifice my 500g based array.
>
> > Hrm... Now I have to figure out how I should migrate my existing system to
> > a RAID5 & LV based system.
>
> I hate computers...
>
> I figured, since my three 500gig drives were now empty, that I would simply
> remove my current 320gig and 400gig drives from the system and install only
> my 500gig drives. Then I'd simply do a fresh installation of Debian and
> finally move any data from my 320 and 400gig drives that I need. This keeps
> all my data on the 320 and 400gig drive safe for the process and should
> result in predictable drive assignments.
>
> Man was I wrong!!!
>
> One drive is a PATA alone as master on the primary IDE controller. The other
> two are SATA on the Intel ICH5 SATA controller. Currently there are no
> drives on the Promise SATA controller (but I do plan on adding another 500g
> here eventually).
>
> I booted the Debian lenny installation disk, got to the point where I'm
> manually partitioning the drives. It's a simple setup.
>
> hda1 - 500meg swap
> hda2 - remainder of hda as RAID5
> sda1 - 400meg swap
> sda2 - 100meg RAID1
> sda3 - remainder of sda as RAID5
> sdb1 - 400meg swap
> sdb2 - 100meg RAID1
> sdb3 - remainder of sdb as RAID5
>
> Looks fine, right?
>
> Well, I created the RAID1 partition. No problems. Formatted it as ext3 and
> to be mounted ro as /boot.
> Now, I go to create the RAID5 partition (which will eventually hold a LV and
> my / partition). I choose create, 3 partitions with 0 spares. Then I get the
> list of available partitions... sda2, sda3 and sdb3. WHAT??? sda2 is already
> allocated to my RAID1! Where's hda2? I cancel the creation. The partition
> display looks normal at this point.
>
> Cursing ensues and I choose to delete a RAID partition. I'm given my list of
> RAID partitions, expecting to only see /md0, but NOOOoooo... I've got a list
> of five choices and none of them will do anything when I choose to delete
> them. Unfortunatly I didn't write the choices down, but they were similar
> to:
>
> /hda0
> :
> /md0
> d0
>
> I've booted the Seagate diagnostics and zero'd all three drives. I go
> through the process again and the exact same thing happens. Needless to say,
> I'm not impressed.
>
> I'm using lenny because etch doesn't properly support the use of the Intel
> PATA controller, Intel ICH5 SATA controller and the Promise SATA controller
> all at the same time.
>
> Does any of this sound familiar? Any idea what is happening?
>
> At this point I'm strongly considering just using another distro, but I
> really liked Debian. I've already got Fedora 8 downloaded. I've tried to
> install it, but I don't see any method of creating a logical volume during
> the install - meaning that I can't put / onto a LV.

I'm doing something similar. I have a Intel ICH6R and have taken 2
500GB drives and created two RAID 0 volumes. I also have 2 nonRAID
drives. on the first RAID volume I installed XP and Vista on part 1
and 2, swap on part 5, SUSE 10.3 in a LVM with 6 partitions on RAID
part 6, and Fedora 8 on part 7. I put the boot partitions on one of
the nonRaid drives. I partitioned the Volume before I installed Linux
because I don't think that Linux can administer Hardware RAID well.
I'm going to add 2 more drives in the last 2 ports and migrate the two
volumes to RAID 5. This is fun but I don't see where it's practical.