Re: Re: Anaconda doesn't support raid10

[Ruslan Sivak <rsivak@xxxxxxxxxxxxx>]

Scott Silva wrote:
> Ruslan Sivak spake the following on 5/7/2007 1:44 PM:
>   
> > Toby Bluhm wrote:
> >     
> > > Ruslan Sivak wrote:
> > >       
> > > > Ross S. W. Walker wrote:
> > > >         
> > > > > > -----Original Message-----
> > > > > > From: centos-bounces@xxxxxxxxxx
> > > > > > [mailto:centos-bounces@xxxxxxxxxx] On
> > > > > > Behalf Of Ruslan Sivak
> > > > > > Sent: Monday, May 07, 2007 12:53 PM
> > > > > > To: CentOS mailing list
> > > > > > Subject:  Anaconda doesn't support raid10
> > > > > >
> > > > > > So after troubleshooting this for about a week, I was finally able
> > > > > > to create a raid 10 device by installing the system, copying the md
> > > > > > modules onto a floppy, and loading the raid10 module during the
> > > > > > install.
> > > > > > Now the problem is that I can't get it to show up in anaconda.  It
> > > > > > detects the other arrays (raid0 and raid1) fine, but the raid10
> > > > > > array won't show up.  Looking through the logs (Alt-F3), I see the
> > > > > > following warning:
> > > > > >
> > > > > > WARNING: raid level RAID10 not supported, skipping md10.
> > > > > > I'm starting to hate the installer more and more.  Why won't it let
> > > > > > me install on this device, even though it's working perfectly from
> > > > > > the shell?  Why am I the only one having this problem?  Is nobody
> > > > > > out there using md based raid10?     
> > > > > >             
> > > > > Most people install the OS on a 2 disk raid1, then create a separate
> > > > > raid10 for data storage.
> > > > >
> > > > > Anaconda was never designed to create RAID5/RAID10 during install.
> > > > >
> > > > > -Ross
> > > > >
> > > > >   
> > > > >           
> > > > Whether or not it was designed to create a Raid5/raid10, it allows
> > > > the creating of raid5 and raid6 during install.  It doesn't, however,
> > > > allow the use of raid10 even if it's created in the shell outside of
> > > > anaconda (or if you have an old installation on a raid10).
> > > > I've just installed the system as follows
> > > >
> > > > Raid1 for /boot with 2 spares (200mb)
> > > > raid0 for swap  (1GB)
> > > > raid6 for / (10GB)
> > > >
> > > > after installing, I was able to create a raid10 device and
> > > > successfully mount and automount by using /etc/fstab
> > > >
> > > > Now to test what happens when a drive fails.  I pulled out the first
> > > > drive - Box refuses to boot.  Going into rescue mode, I was able to
> > > > mount /boot, was not able to mount the swap drive (as to be expected,
> > > > as it's a raid0), was also not able to mount the / for some reason,
> > > > which is a little surprising.
> > > > I was able to mount the raid10 parition just fine.
> > > > Maybe I messed up somewhere along the line.  I'll try again, but it's
> > > > disheartening to see that a raid6 array would die after one drive
> > > > failure, even if it was somehow my fault.
> > > > Also assuming that the raid5 array could be recovered, what would I
> > > > do with the swap partition?  Would I just recreate it from the space
> > > > in the leftover drives and would that be all that I need to boot?
> > > > Russ
> > > >
> > > >
> > > >         
> > > Russ,
> > >
> > > Nothing here to help you (again - :) just looking down the road a
> > > little. If you do get this thing working the way you want, will you be
> > > able to trust it to stay that way?
> > >
> > >       
> > Well, it's been my experience, that in linux, unlike windows, it might
> > take a while to get things the way you want, but once you do, you can
> > pretty much trust it to stay that way.
> > So yea, this is what I'm looking to do here.  I want to set up a system,
> > that will live after 1 (or possibly 2) drive failures.  I want to know
> > what I need to do ahead of time, so that I can be confident in my set
> > up, and know what to do in case disaster strikes.
> >
> > Russ
> >     
> If you have the hardware, or the money, you can make a system pretty durable.
> But you get to a point that the gains aren't worth the cost. You can get a
> system to 3 "9's" fairly easy, but the cost to get to 4 "9's" is much more. If
> you want something better than 4 "9's", you will have to look at clustering,
> because a single reboot in a month can shoot down your numbers.
>
> If you want total reliability, you will need hot spares and a raid method that
> builds quickly, and you will need regular backups.
>
>   
I'm not looking for total reliability.  I am building a low budget 
file/backup server.  I would like it to be fairly reliable with good 
performance.  Basically if 1 drive fails, I would like to still be up 
and running, even if it requires slight reconfigurations (ie recreating 
the swap partition). 

If 2 drives fail, I would like to still be able to be up and running 
assuming I wasn't unlucky enough to have 2 drives fail in the same 
mirror set. 

If 3 drives fail, I'm pretty much SOL. 

The most important thing is that I can easily survive a single disk 
failure. 

Russ
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