[mythtv-users] Recording directly to RAID

Steven Adeff adeffs.mythtv at gmail.com
Fri Jul 27 20:27:16 UTC 2012

On Fri, Jul 27, 2012 at 4:15 PM, Tapani Tarvainen
<mythtv at tapanitarvainen.fi> wrote:
> On Jul 27 13:27, David Engel (david at istwok.net) wrote:
>> Is anyone recording directly to RAID?  If so, what type/size, how many
>> simultaneous recordings and how well does it work?
> I've got a 5-disk RAID10 array in a fileserver used by
> mythtv over NFS in addition to one local disk.
> It can handle 10 simultaneous recordings without blinking.
> (Or at least could once when I tested it - besides that I don't
> think I've ever had more than five.)
> And the disks aren't particularly fast either: 2TB Seagate Green
> 5900 rpm disks. But in the RAID10 setup they can pull rather
> impressive speeds, writing over 300MB/s and reading 600MB/s
> for single stream, and what's more, multiple simultaneous
> processes get almost the same in aggregate.
> Key there was using offset (o2) layout with biggish (4M) block size -
> defaults are rather ridiculous.
> Enough RAM and good SATA controller are also important.
> (I like LSI HBA cards.)
>> The two configurations I'm primarily considering are either a 4-disk
>> RAID6 array or a pair of 2-disk RAID1 mirrors.  While the RAID6
>> configuration should be more reliable, in theory, I'm leaning toward
>> the RAID1 configuration.  One big reason, and the reason for this
>> email, is the increased seek load on all drives with RAID6 when 4 or
>> more recordings are in-progress.
> With four disks I'd go for RAID10 without question.

I used to have a 6 disc RAID5 for recordings. I left that to go with
storage groups instead. I actually increased my overall read write
speeds with multiple recordings/playbacks. At peak times I can have
7-8 recordings with up to 3 playbacks and 4 commflag sessions going on
at once "without skipping a beat".

RAID, unless redundancy is required of your recordings, is not
necessary since the introduction of storage groups.

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