[mythtv-users] LVM RAID 5 partition schemes

David myth at dgreaves.com
Wed Apr 6 18:50:46 UTC 2005


Milan Andric wrote:

>Hello,
>
>I'm planning on sqeezing as much as I can into a microATX case
>to make my mythtv frontend/backend. I also want to make this
>a media storage box/file server, ie. include a RAID 5 LVM storage setup.
>  
>
It'll be noisy and, more worryingly - very hot!

>I'm basically stuck on the RAID.  Since I  do not have enough data
>*right now* to use the 3 x 300G RAID 5,  I'd like to just buy two
>drives now and use mdadmin to
>setup a RAID 5 with 2 missing drives and add drives as time goes on.
>  
>
nope - can't do that :)
You can start with a 3-drive raid5 with 1 missing (ie 2x300Gb) and add a 
3rd later.

But you'll have no redundancy until you buy the 3rd drive.
You also can't 'add drives as time goes by' to a raid 5.
You could buy another 3 drives and setup another 3drive raid5 and add it 
to your lvm but that's not what you meant.

[you could also investigate EVMS - it does allow you to 'grow' raid5 - 
but it can fail and backups are strongly suggested...]

>I know it's required to have 3 drives to make a RAID 5 array.  But is
>there a way to fake so I can add a third drive later?  Or do I just
>have to fork up the cash now?
>  
>
so yes you can use the 'missing' keyword to fake the 3rd drive.

>If you could post your partition scheme or how you setup 
>your partitions/drives it would help me.
>  
>
see the wiki - I wrote a step-by-step there...
http://www.mythtv.info/moin.cgi/AdministrationSoftware_2fLvmRaid

>Has anyone tried to mix/match devices like ATA and SATA to create a raid 5 with
>md? I know it's crazy but i'm just trying to consider the options for
>the time being.
>  
>
yes.
I have 6x250 Gb sata drives making a raid5 array
The 6th 'spare' drive is a 250Gb partition on a 300Gb PATA drive - and I 
have had it as part of the array with no issues at all.

>Here's some of my proposed hardware setup (still in the works) :
>  
>
mostly fine

>Case:
>Cooler Master ATC-620C-BX1 Cases microATX Form
>http://www.newegg.com/app/viewProductDesc.asp?description=11-119-024&depa=0
>  
>
This'll hurt - search the lkml for issues that eventually trace to poor 
PSU or overheat with multiple drives...

HTH
David



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