[mythtv-users] LVM RAID 5 partition schemes

[Milan Andric]

On Apr 6, 2005 11:50 AM, David <myth at dgreaves.com> wrote:
> 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!

Yeah I'm obviously worried about that, figured there's only one way to
find out ...

there's probably no way around the noise ... for now until i can make a backend
in a basement or somewhere. right now i have an apt. i'm beginning to 
think i'll need to stick the fileserver in a tower/desktop case.

what type of case do you suggest as a minimum for raid 5, + OS drive?
ie. 3-5 drives.  

so minimally, i'd create the raid 5 and os paritions on 3 drives with
missing trick for expansion.
1 SATA 300G
   sda1 - 250G (raid 5 - 1)
   sda2 - 50G  (raid1 - 1)

1 SATA 300G
   sda1 - 250G (raid 5 - 2)
   sda2 - 50G (raid1 - 2)

1 ATA 250G (this i might add in the future. an identical drive is ideal but ...)
   hda1 - 250G (raid 5 - 3)

if i change my route from microATX behemoth I'd likely make my current 
desktop computer a file-server/myth backend and purchase HW
for a frontend.  

there's a problem with that.
1) no wired network to bedroom, just wireless 802.11B 5-8Mb/s?

but it does cost about the same since i'll just stick those drives and 
SATA card into my desktop.  a diskless frontend would be best and
probably cheaper.  i wonder what a diskless frontend goes for these days?

i was thinking a mediaMVP might do the trick ... 
http://www.hauppauge.com/html/mediamvp_datasheet.htm
but for watching mpeg4 video? 
n the past i usually schedule my mpeg2 files to be compressed.  figure
there's got to
be something else out there.


> 
> >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.

unless i use the 'missing' trick?


> 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.

dang. what case do you use? and powersupply/fan?

> 
> >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...

ok, thanks.

-- 
Milan