[CentOS] Re: Anaconda doesn't support raid10

Mon May 7 21:43:26 UTC 2007
Ruslan Sivak <rsivak at istandfor.com>

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 at centos.org
>>>>>> [mailto:centos-bounces at centos.org] On
>>>>>> Behalf Of Ruslan Sivak
>>>>>> Sent: Monday, May 07, 2007 12:53 PM
>>>>>> To: CentOS mailing list
>>>>>> Subject: [CentOS] 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