[NBLUG/talk] RAID1 and partitions

[Omar Eljumaily]

Thanks Mark.  Right now the machine has 4 gb of RAM, but the production 
version will probably have 16 gb. Just one CPU with probably 6 cores.  
I've always wondered about swap, whether it's really needed if you have 
enough RAM.

I've noticed that Ubuntu doesn't automatically delete old system files 
in /boot, so probably a fairly large boot partition will make things easier.

LVM is a big gray area for me.  If I want as swap partition without 
having to do another RAID volume wouldn't it be necessary?  For that 
matter could I do an ext4 /boot partition in the same volume as swap and 
/?  Probably better to do just what is normal and use ext2, but I'm just 
wondering.

One aspect of RAID1 is the ability do a live 100% accurate mirror and 
put the disk aside as a system configured backup.  That isn't easily 
done with any other technology I can think of.  It involves degrading a 
drive while it rebuilds itself, but it can be done after hours and slow 
times.  The alternative would be a 5 hour/ terrabyte offline Clonzilla 
backup.  Maybe there are ways to cobble that function together using 
rsync, but it wouldn't be easy.

Thanks,

Omar


On 5/1/2015 6:59 PM, Mark Street wrote:
> Hi,
>
> I would go with your gut.  Putting swap on md0 just does not sound 
> like a good thing to do.  Your experience with CentOS is similar to 
> what I have done in the past.  Is this software RAID?  How much RAM 
> and CPU do you have?  Depending on your answer you may not need much 
> swap.  If any, put it at the end... or create a swap file on /
>
> I have been running some old mail servers for over 8 years on software 
> raid 5 with 4 drives, only 1 drive failure the whole time.  Still 
> chugging along... it's an old Penguin Altus 1400 1U. Still kicks ass 
> with the old Opterons and 16G of RAM.
>
> Keep /boot on md0 and use ext2, nothing wrong with that.  Good stable 
> filesystem.  If you feel you need the LVM go with it or just use ext4 
> for /, your filesystem structure seems really basic.  I have done both 
> in hardware and in VM environments with few issues.
>
> Best Regards,
>
>
> On 5/1/2015 10:23 AM, Omar Eljumaily wrote:
>> Does anybody have any tips for setting up a RAID1 array on Ubuntu?
>>
>> I've looked at this:
>>
>> https://help.ubuntu.com/lts/serverguide/advanced-installation.html
>>
>> It suggests setting up
>>
>> md0 as a swap partition and
>> md1 as an ext4 / partition which is also bootable.
>>
>> My experience with Centos is to do:
>>
>> md0: /boot with ext2
>>
>> md1: as an LVM volume creating partitions:
>>
>> swap
>> and / as ext4
>>
>> My goal is reliability and to be able to boot into either volume when 
>> the other is degraded.  Is there any standard way to do this?
>>
>> Thanks,
>>
>> Omar
>>
>>
>>
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