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Old 06-25-2008, 05:35 PM
"Ross S. W. Walker"
 
Default preferred software RAID 10?

Rudi Ahlers wrote:

> Hi all
>
> I'm looking at setting up software RAID 10, using CentOS 5.1 x64 - what
> is the best way todo this?
>
> I'm reading some sources on the internet, and get a lot of different
> "suggestions"
>
> 1 suggestion says to boot up with a Live CD like Knoppix or
> SystemRescueCD, setup the RAID 10 partitions, and then install Linux
> from there.
> 2. Another is to setup a small RAID 1 on the first 2 HDD's, install
> Linux, bootup, and then setup the rest as RAID 10
>
> The others didn't really make sense to me, so how do I
> actually do this?
>
> And then, how do I setup the partitioning? Do I setup /boot on a
> separate RAID "partition"? If so, what happens if I want to
> replace the 1st 2 HDD's with bigger ones?

What's the hardware setup?

-Ross

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Old 06-25-2008, 05:47 PM
Rudi Ahlers
 
Default preferred software RAID 10?

Ross S. W. Walker wrote:

Rudi Ahlers wrote:



Hi all

I'm looking at setting up software RAID 10, using CentOS 5.1 x64 - what
is the best way todo this?


I'm reading some sources on the internet, and get a lot of different
"suggestions"


1 suggestion says to boot up with a Live CD like Knoppix or
SystemRescueCD, setup the RAID 10 partitions, and then install Linux
from there.
2. Another is to setup a small RAID 1 on the first 2 HDD's, install
Linux, bootup, and then setup the rest as RAID 10


The others didn't really make sense to me, so how do I
actually do this?


And then, how do I setup the partitioning? Do I setup /boot on a
separate RAID "partition"? If so, what happens if I want to
replace the 1st 2 HDD's with bigger ones?



What's the hardware setup?

-Ross

__________________________________________________ ____________________

I didn't really specify any, cause I want to keep it purely software.
Generally it would be on a generic PIV motherboard with 4 / 6 SATA, or
even mixed SATA & IDE HDD's - all new, so at least 80GB per HDD


--

Kind Regards
Rudi Ahlers
CEO, SoftDux

Web: http://www.SoftDux.com
Check out my technical blog, http://blog.softdux.com for Linux or other technical stuff, or visit http://www.WebHostingTalk.co.za for Web Hosting stuff

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Old 06-25-2008, 05:58 PM
John R Pierce
 
Default preferred software RAID 10?

Rudi Ahlers wrote:
And then, how do I setup the partitioning? Do I setup /boot on a
separate RAID "partition"? If so, what happens if I want to replace
the 1st 2 HDD's with bigger ones?



each partition is raided seperately with mdadm.... you could make the
whole thing one LVM partition thats raid10, then use LVM to dice it up
into file systems.


if you have 4 drives and are doing software raid10, you won't be
swapping drives with different sizes without a WHOLE lotta pain.


/boot shouldn't be mirrored, as the BIOS won't know how to boot it.
leave /dev/sdb1 the same size as /dev/sda1 and call it /boot2 and try to
remember to copy /boot to /boot2 each time you update the kernel.

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Old 06-25-2008, 06:06 PM
"Joseph L. Casale"
 
Default preferred software RAID 10?

>/boot shouldn't be mirrored, as the BIOS won't know how to boot it.

Not true for all mobo's. Regardless, why not have a copy safe somewhere
easier to manage then the following suggestion IMHO. Let the computer
worry about remembering to copy it.

>leave /dev/sdb1 the same size as /dev/sda1 and call it /boot2 and try to
>remember to copy /boot to /boot2 each time you update the kernel.


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Old 06-25-2008, 06:29 PM
Florin Andrei
 
Default preferred software RAID 10?

John R Pierce wrote:


/boot shouldn't be mirrored, as the BIOS won't know how to boot it.


Wait. I thought mirror RAID is the same on-disk format like a plain
partition, so therefore a mirrored /boot will always boot. At least, it
always did for me.


--
Florin Andrei

http://florin.myip.org/
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Old 06-25-2008, 06:30 PM
"Ross S. W. Walker"
 
Default preferred software RAID 10?

Rudi Ahlers wrote:

> Ross S. W. Walker wrote:
> > Rudi Ahlers wrote:
> >
> >> Hi all
> >>
> >> I'm looking at setting up software RAID 10, using CentOS 5.1 x64 - what
> >> is the best way todo this?
> >>
> >> I'm reading some sources on the internet, and get a lot of different
> >> "suggestions"
> >>
> >> 1 suggestion says to boot up with a Live CD like Knoppix or
> >> SystemRescueCD, setup the RAID 10 partitions, and then install Linux
> >> from there.
> >> 2. Another is to setup a small RAID 1 on the first 2 HDD's, install
> >> Linux, bootup, and then setup the rest as RAID 10
> >>
> >> The others didn't really make sense to me, so how do I
> >> actually do this?
> >>
> >> And then, how do I setup the partitioning? Do I setup /boot on a
> >> separate RAID "partition"? If so, what happens if I want to
> >> replace the 1st 2 HDD's with bigger ones?
> >>
> >
> > What's the hardware setup?
> >
>
> I didn't really specify any, cause I want to keep it purely software.
> Generally it would be on a generic PIV motherboard with 4 / 6
> SATA, or even mixed SATA & IDE HDD's - all new, so at least 80GB per HDD

I was primarily interested in the # of HDDs that can be used.

If you have 6 disks, setup 2 disks as a RAID1 for the OS and the
other 4 as a RAID10 for the data.

If you have 4 disks all together:

1) create /boot partition as a 4 disk RAID1 across all 4 disks

2) create the remaining space as 2 separate RAID1s of type LVM

3) create a VG out of the 2 RAID1 PVs, create root, swap LVs on
the VG with a stripe of 2.

LVM striping over multiple RAID1 PVs provides the same performance
as a native RAID10 array, plus you can add RAID1s later to
increase the size/performance and dump/restore the data to stripe
it across the larger set of PVs.

-Ross

__________________________________________________ ____________________
This e-mail, and any attachments thereto, is intended only for use by
the addressee(s) named herein and may contain legally privileged
and/or confidential information. If you are not the intended recipient
of this e-mail, you are hereby notified that any dissemination,
distribution or copying of this e-mail, and any attachments thereto,
is strictly prohibited. If you have received this e-mail in error,
please immediately notify the sender and permanently delete the
original and any copy or printout thereof.

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Old 06-25-2008, 06:35 PM
"Ross S. W. Walker"
 
Default preferred software RAID 10?

Florin Andrei wrote:

> John R Pierce wrote:
> >
> > /boot shouldn't be mirrored, as the BIOS won't know how to boot it.
>
> Wait. I thought mirror RAID is the same on-disk format like a plain
> partition, so therefore a mirrored /boot will always boot. At
> least, it always did for me.

Yes, default md format stores meta data at end of storage unit so it
is accessible outside of raid configuration.

-Ross

__________________________________________________ ____________________
This e-mail, and any attachments thereto, is intended only for use by
the addressee(s) named herein and may contain legally privileged
and/or confidential information. If you are not the intended recipient
of this e-mail, you are hereby notified that any dissemination,
distribution or copying of this e-mail, and any attachments thereto,
is strictly prohibited. If you have received this e-mail in error,
please immediately notify the sender and permanently delete the
original and any copy or printout thereof.

_______________________________________________
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Old 07-17-2008, 09:10 PM
Rudi Ahlers
 
Default preferred software RAID 10?

John R Pierce wrote:

Rudi Ahlers wrote:
And then, how do I setup the partitioning? Do I setup /boot on a
separate RAID "partition"? If so, what happens if I want to replace
the 1st 2 HDD's with bigger ones?



each partition is raided seperately with mdadm.... you could make the
whole thing one LVM partition thats raid10, then use LVM to dice it up
into file systems.


if you have 4 drives and are doing software raid10, you won't be
swapping drives with different sizes without a WHOLE lotta pain.
Ok, so how do I do this? Let's say I have 4x 160GB HDD's now, and plan
on replacing them with 4x 500GB HDD's in the future?


What setup would help with a upgrade in the future?


/boot shouldn't be mirrored, as the BIOS won't know how to boot it.
leave /dev/sdb1 the same size as /dev/sda1 and call it /boot2 and try
to remember to copy /boot to /boot2 each time you update the kernel.
I understand this, but how do you boot from /boot2 on the second HDD if
the 1st have failed?


--

Kind Regards
Rudi Ahlers

Check out my technical blog, http://blog.softdux.com for Linux or other technical stuff

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Old 07-17-2008, 10:31 PM
Kai Schaetzl
 
Default preferred software RAID 10?

Rudi Ahlers wrote on Thu, 17 Jul 2008 23:10:48 +0200:

> > /boot shouldn't be mirrored, as the BIOS won't know how to boot it.
> > leave /dev/sdb1 the same size as /dev/sda1 and call it /boot2 and try
> > to remember to copy /boot to /boot2 each time you update the kernel.
> I understand this, but how do you boot from /boot2 on the second HDD if
> the 1st have failed?

You don't (*). I don't understand John's advice here. There is no problem
md mirroring /boot. You just need to install grub a second time on the
other disk. For that you have to boot from it. (I think I also did it
successfully without booting from the other disk in the past, but last
time I tried it it didn't want to work like I remembered it should.)

(*) Anyway, you would boot from a Rescue CD or such and rename it ...

Kai

--
Kai Schätzl, Berlin, Germany
Get your web at Conactive Internet Services: http://www.conactive.com



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Old 07-17-2008, 10:39 PM
"Ross S. W. Walker"
 
Default preferred software RAID 10?

Rudi Ahlers wrote:
> John R Pierce wrote:
> > Rudi Ahlers wrote:
> >> And then, how do I setup the partitioning? Do I setup /boot on a
> >> separate RAID "partition"? If so, what happens if I want to replace
> >> the 1st 2 HDD's with bigger ones?
> >
> >
> > each partition is raided seperately with mdadm.... you could make the
> > whole thing one LVM partition thats raid10, then use LVM to dice it up
> > into file systems.
> >
> > if you have 4 drives and are doing software raid10, you won't be
> > swapping drives with different sizes without a WHOLE lotta pain.
>
> Ok, so how do I do this? Let's say I have 4x 160GB HDD's now, and plan
> on replacing them with 4x 500GB HDD's in the future?

Personally I would never put an OS install on a higher RAID then RAID1,
because it gets too messy to upgrade like you suggested.

>
> What setup would help with a upgrade in the future?
>
> >
> > /boot shouldn't be mirrored, as the BIOS won't know how to boot it.
> > leave /dev/sdb1 the same size as /dev/sda1 and call it /boot2 and try
> > to remember to copy /boot to /boot2 each time you update the kernel.
>
> I understand this, but how do you boot from /boot2 on the
> second HDD if the 1st have failed?

Could you not get a system that had 2 drives for the OS and 4 drives
for data?

I have setup 4 disk RAID10 systems before, but they were never
intended to be upgraded (in place at least).

I can forward a couple of recipes, but let me first say that to do
it from the CentOS install media requires 2 RAID1s and LVM striping
because the RAID10 option isn't on the media, but it is functionally
equivalent both in useable space and performance.

If you want to use the MD RAID10 driver you need to build it from a
working system then install on it.

-Ross

__________________________________________________ ____________________
This e-mail, and any attachments thereto, is intended only for use by
the addressee(s) named herein and may contain legally privileged
and/or confidential information. If you are not the intended recipient
of this e-mail, you are hereby notified that any dissemination,
distribution or copying of this e-mail, and any attachments thereto,
is strictly prohibited. If you have received this e-mail in error,
please immediately notify the sender and permanently delete the
original and any copy or printout thereof.

_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 

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