[mythtv-users] backend storage performance needs?

[Tim Draper]

 ---- On Tue, 19 May 2020 11:44:41 +0100 Jim Abernathy <jfabernathy at gmail.com> wrote ----
 > Just an opinion request here.  When I built my current backend it was an 
 > old motherboard with lots of SATA II (3Gb/s) ports. I was worried about 
 > the need to have 2 recording drives defined so 2 simultaneous recordings 
 > would go to different drives.
 > 
 > I also wanted RAID mirrors so I used 4-2TB drives with mdadm RAID 1. A 
 > lot to maintain as drives do fail and RAID volumes have to be replaced 
 > and rebuilt. Replacing and rebuilding has occurred on average of once a 
 > year.
 > 
 > So the question is, if I bought a new motherboard with SATA III (6Gb.s) 
 > ports and new SATA III high performance hard drives would I really need 
 > to define 2 recording drives? i.e. use 2-4TB drives in RAID 1 mirror 
 > configuration.
 > 
 > My tuner is a PCIe Hauppauge WinTV Quat HD. I have 4 tuners defined with 
 > each tuner having a maximum recordings of 2. But I've never recorded 
 > more than 4 channels at once with some back-to-back programs on the same 
 > channel.
 > 
 > With the current speed of processors, serial connections, and hard 
 > drives do I still need 2 recording drives defined?
 > 
 > Since SSDs and RAID is not recommended, I avoided that in the discussion.
 > 
 > Jim A
 > 
 > 
i run dual DVB-S2 tuner to a 2.5" 500gb laptop drive. plus playback on 1 tv. it handles things fine although thats only upto 1080i broadcast content (UK freesat). I think i estimate around 10MB/s per video feed as the absolute minimum although more performance is always experienced. take a look at the size of one of your recordings divide by runtime in seconds, and thats your file MB/sec. times that by tuners, plus some overhead (say 20%) and that'll be your minimum requirement.

i'm currently moving off the 2.5" to raid1 WD Red's for my recordings - i found some old un-used disks that are bigger than what i currently have plus i need to expand on disk space too.

any new 3.5" drive (WD Reds for example) should be seeing around 140MB/sec peak. my (i think) 1st gen 4TB WD Red drives can handle 1gig NIC throughput maxed out and anything local on the server sees higher than that by 20%.
while red's are rated for NAS, i dont beleive mdadm requires such disks but would definately recommend disks rated for 24/7 use reguardless of what they are. Raid-rated disks are more for hardware raid rather than mdadm's software implimentation.