[mythtv-users] Question re: available SATA ports and linux software RAID

Jos Hoekstra joshoekstra at gmx.net
Fri Apr 8 00:42:35 UTC 2011

Op 8-4-2011 0:25, Bobby Gill schreef:
> Wow, a lot of info here, can't thank you all enough! The elaborations 
> on the SAS and HighPoint cards is especially appreciated, hate to 
> think I could've gone and done the whole thing without knowing those 
> little tidbits.
> I perhaps should have been clearer as to the usage of my server: It 
> will be primarily for streaming media (.mkv, rare .avi, etc. video 
> files + mp3s) via XBMC and Myth [recordings of course] directly to a 
> receiver via HDMI. Minimally I'll be streaming wirelessly to laptop 
> around the house, but that first purpose is it for the most part.
> So now 3 questions arise:
>     RAID is for availability, rather than backup, so unless you like
>     the idea of
>     doing unscheduled OS/MythTV reinstalls/restores, then it might be
>     a good
>     idea to put your OS on more than one drive too.
> 1. ^^^^ I don't understand what you mean by unscheduled OS/MythTV 
> reinstalls/restores. I back up my crucial OS configs and the myth 
> database and relevant stuff regularly to a few external drives and 
> online space. I think the idea is that I can just have a small drive 
> (I have several of various sizes 250gb-750gb) with the OS on it, 
> separate from the array should one of the larger RAID drives fail and 
> I have to go through the whole rebuilding deal or something, so that 
> the machine is still usable even if the data is on hold or whatnot. I 
> am sure I'm misunderstanding or overlooking some aspect of this and 
> would greatly appreciate it if someone can point to why it'd be better 
> to put the OS on the RAID array than a separate smaller drive.

Some people hate downtime even when the OS-disk fails, most choose to 
solve that by using a raid1 volume as boot. It makes failure a bit les 

>     For an non raid card I recommend the following controller under linux:
>     http://www.newegg.com/Product/Product.aspx?Item=N82E16816117157&cm_re=intel_sas-_-16-117-157-_-Product
>     <http://www.newegg.com/Product/Product.aspx?Item=N82E16816117157&cm_re=intel_sas-_-16-117-157-_-Product>
>     John
> 2. ^^^^ If I get this card, to be clear for my thick skull hehe, a) it 
> is basically adding SATA ports to my motherboard to which I can 
> connect my drives as normal, and then set up a linux software RAID, 
> correct? and b) It specifies "RAID 0/1/1E/10E" but that is only if I 
> use it as a hardware RAID card, correct? (in other words irrelevant 
> since I'd use linux software RAID?)

Yup, put it in IT-mode and it'll pass on the disks to the OS. You'll 
need SFF-8087 cable to 7 pin SATA for that though(can be had cheaply via 

> 3. It's looking like RAID6 is a better choice. For the cost I do not 
> mind losing some space for better protection, if that's how one can 
> deem it. I just used this RAID calculator: 
> http://www.icc-usa.com/raid-calculator.asp  and it shows that if I 
> have 8x2TB for example in RAID6, I'd have 12GB usable. This is 
> acceptable to me. My question is about having extra drives to swap for 
> failed ones: a) Must the drives all be 100% exactly the same and b) 
> How many would be advisable to have on hand? (sticking with the 8x2 
> example).
> Thank you all for your time and help, greatly appreciated!!
> Bobby

They're prefferably 100% the same, but if you foresee mixing and 
matching: create partitions that are just a bit smaller than the 
disk-size to give yourself some room to play with. So on 2 TiB make the 
partition something likt 1990 GiB., then you can do some mixing and 
matching easier. I'd advise 1 or two, recently had a failure and chucked 
in another disk, had it rebuild and now have time to RMA the other one.  
if you wait longer and another disk fails you're on thin ice 
rebuilding(which hammers the disks).

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