Re: [PLUG] Linux (Debian) and raid

["Brian Stempin" <brian.stempin@gmail.com>]

To those of you who are feeling iffy about setting up a software RAID:

Setting up software RAID in linux is very similar to the process of setting up a software RAID in Windows 2003 (I'm a windows admin by day, but my side business all runs on linux).  At one point in time, I was hosting a development environment for a website, which consisted of a web server and a MySql server (separate boxes).  I took the opportunity to learn how to set up SW RAID while constructing these machines.  Using the Ubuntu installer, RAID is very easy to set up during the installation of the OS.  After installing a fresh RAID and the OS (in this case, Ubuntu 
6.06 LTS), I decided to play around with the MD tools.  They are very simple and straight forward.

> For all that makes Linux the powerful OS it is, it also makes it an OS
> that will never be a day to day staple for the masses. The file system is
> a big part of the benefit and problem of Linux. I mean who wants to deal
> with multiple partitions, of different filessystems, and on top of that a
> level of raid. For some it is a challenge and at times I find it very
> intimidating.

Setting up SW RAID doesn't get much simpler than the MD tools.  If multiple partitions intimidate you, then perhaps you should reconsider your approach to RAID.  In order to be fluent in RAID operations such as recovering, degrading, and upgrading arrays, you need to be comfortable with the file system(s) and partition(s) that are at hand.  Even in a Windows environment, I rarely set up a server with less than 2 partitions.  Dealing with partitions is just a fact of life when it comes to server administration.  If you're intimidated by partitions and the like now, then you'll really be intimidated when it comes time to try to recover a degraded array that hosts some sort of critical partition.  I would recommend becoming more familiar with disk partitioning, etc before implementing a RAID.  Otherwise, RAID just becomes a complication that can't be effectively used or managed.  My 2c.  HTH,

Brian

On 5/25/07, Russ Wenner <russwenner@gmail.com> wrote:

Hello All,

I have been following this thread with interest because I too have
plans to run RAID on a Linux Server.

As a Windows admin I find myself most comfortable in Windows but I am
learning everything I can about Linux and implementing everywhere I
can.

Anyway...I have been frequently using Webmin to help me (a Windows
guy) configure some things.  In Webmin one of the selections under
"Hardware" is "Linux RAID".

I was thinking that I would be giving Webmin a try in configuring RAID.

--
Russ

On 5/25/07, Doug Crompton <doug@crompton.com> wrote:
> Now that I read all this I remembr why I never implemented raid before. I
> go with simplicity and this just adds another level of complication. I
> like Linux and I like it's capabilities BUT I am not fanatical about it
> like many are. I use Windows equally as much or maybe more. linux is in
> the background here although it has a big place. I just don't interact
> with it as much on a day to day basis as Windows.
>
> For all that makes Linux the powerful OS it is, it also makes it an OS
> that will never be a day to day staple for the masses. The file system is
> a big part of the benefit and problem of Linux. I mean who wants to deal
> with multiple partitions, of different filessystems, and on top of that a
> level of raid. For some it is a challenge and at times I find it very
> intimidating.
>
> I have had just about every version of windows over the years and have
> never used it with more than ONE partiition. That has always worked fine
> for me. It is easy to back up and easy to recognize. you know what it is -
> the whole drive is one OS. Yes the argument could be made that it is
> easier and more fatal to screw up one partition then many but most failure
> modes I have experienced are catastrophic across the whole drive.
>
> I guess I have to examine my reason for raid. In Windows raid 1 (at least
> with he Intel MB's) works the way I would like it to. It keeps two
> identical copies of drives that can function as standalone drives. I could
> take either of my drives from my raid array and throw them in a virgin,
> non raid, system and they would boot windows. I want to be able to have
> this same capability in Linux. Just a simple, write the same thing to both
> drives redundancy. I don't think that is possible and the level of
> complexitiy of raid under Linux, especially SW raid, if appears to me adds
> another failure mode or at least complexity that would have to be dealt
> with in a failure.
>
> Maybe automated backups would be a better choice! Certainly raid does not
> or should not prclude backups anyhow.
>
> Doug
>
> On Fri, 25 May 2007, sean finney wrote:
>
> > hi doug,
> >
> > first, to follow up on mark's comment:
> >
> > On Friday 25 May 2007 06:40, Doug Crompton wrote:
> > > On Fri, 25 May 2007, Mark M. Hoffman wrote:
> > > > 1) Most onboard RAID controllers do most of the work in software anyway.
> > > >
> > > > 2) If your board dies, you'll have to replace it with one that has that
> > > > same controller.  With software RAID, any board that can connect to the
> > > > disks can be used in a pinch.
> >
> > i have to say i agree here.  unless you're running a really high-performance
> > server (and maybe not even then, istr benchmarks putting md not to far from
> > some of the "hardware" implementations), i'd say software raid is a better
> > choice.  one more reason that mark didn't bring up is the tools and
> > reliability of software raid vs hardware raid.  typically with hw raid you
> > don't see the physical devices, which means you can't do things like running
> > smartd to query their status... so you only know about a failed disk after it
> > has failed.
> >
> > > Well not sure what happens in linux but in windows I have experience with
> > > thie. My board did die and I needed to get info to a new system. All I did
> > > was attach one of the raid 1 mirrored drives to the new system. It saw it
> > > as a standalone drive and I was able to read from it fine.
> >
> > i wouldn't rely on that feature to work across all raid systems...
> >
> > > > I've done software RAID w/ CentOS.  I set it up like this:
> > > >
> > > > /dev/hda1 and /dev/hdc1 => /dev/md0 (raid1) => /boot
> > > >
> > > > /dev/hda2 => swap
> > > > /dev/hdc2 => swap
> > > >
> > > > /dev/hda3 and /dev/hdc3 => /dev/md1 (raid1) => /dev/VolGroup00 (LVM)
> > > >
> > > > The remaining partitions are allocated on the LVM volume.
> > >
> > > I was trying to avoid the complication of LVM, etc. I just want ext3 or
> > > equiv partitions and mirrored raid.
> >
> > i'd suggest you give it a second shot.  i was really late jumping onto the LVM
> > bandwagon, but it's quite nice.  plus, the debian installer has built-in
> > support for it.   otherwise, you'll need to create a raid device for each
> > partition (istr being able to sub-partition a raid device, but never actually
> > did it).
> >
> > the only gotcha is you can't have /boot (or /, if it's the same thing) on lvm
> > (i hear there's a google SoC to add support for this into grub, but...) so
> > like mark suggested, you can set up one RAID device for /, and a second raid
> > device to act as a physical volume for lvm.
> >
> >
> >       sean
> >
>
>
> "Those that sacrifice essential liberty to obtain a little temporary safety
>  deserve neither liberty nor safety."  -- Ben Franklin (1759)
>
> ****************************
> *  Doug Crompton           *
> *  Richboro, PA 18954      *
> *  215-431-6307            *
> *                          *
> * doug@crompton.com        *
> * http://www.crompton.com  *
> ****************************
>
>
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--
Russ
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___________________________________________________________________________
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