[mythtv-users] What is best filesystem for recordings?

[Warpme]

On 30/06/15 14:20, Andre Newman wrote:
>
> I’m interested in how you get on with the Archive drive, shingled tracks I believe? Not happy about buying a Seagate (ever again) but HGST start to launch some shingled archive drives too.
Yeah. Me too about Seagate...but here in Poland, 8T archive has 
unmatched $/GB. It is 20% lower that currently best in this class 4T drives.
I was thinking over week: should I go with 8T from Seagate.
I took risk :-p
I copied already over 2.9T movies to this drive. It performs 
surprisingly well with write speed: top is 120MB/s, avg 90-95MB/s.
Unfortunately I didn't check speed sustainability - but I'm expecting 
not good results here.
Here are some details: 
http://www.storagereview.com/seagate_archive_hdd_review_8tb
But as this drive will be used _exclusively_ for movies (so practically 
no rewrites) I believe it is good trade-off.

> I have 4x4TB and 2x6TB for media archives, work media not just movie rips, ok a lot are movie rips, will be needing some more space soon.
I think these 20% lower cost that best $/GB is worth to go with 
assumption that drive use-case will app with minimal rewrites.
Mythvideo storage is perfect candidate I think.
> I always use ext4 for videos and xfs for recordings, concurrency seems better in xfs than ext4, I remember that cpu load was higher but corruption due to lost dvb packets was much lower.
For recordings currently I tend to go with EXT4 rather than with JFS.
XFS is last candidate due asynchronous journal write strategy. It is 
good for performance - but without guaranteed power supply it seems to 
be worse choice than JFS (which has synchronous journal write strategy).
Of course XFS can be asked for synchroneius staregy - but default async 
means XFS design was optimized for max performance with assumption that 
minimal power interruptions are provided by extra solutions like APS.
>
> A much bigger effect I have seen for recordings drives is switching to AV drives, WD AV-GP, Seagate Pipeline or Hitachi Cinema. I have run tests with 19 simultaneous HD recordings spread across four WD AV-GP 3TB drives with no visible dvb packet loss, 24 simultaneous was a big mess! The AV drives seem to seek a lot less than regular desktop drives under the same load.
This is interesting.
I done tests with 16 concurrent HD rec:
a.1x4T, WD green, ext3
b.2x4T, WD + Seagate, ext3

For a. it goes OK but I had regular TFW warnings. Despite that  all 
recording were OK. IOwait was like 45-55%

For b. all was OK, no TFW and not any issues with recordings. IOwait was 
25-35%

HW was Intel DH67BL + i3220T.
> This is a lot of simultaneous HD for only two drives! I usually think 4 per drive is absolute max, pref  3.
4? Why such benchmark?
10 rec. with 6-7Mbps avg. each gives 60-70Mbps. Today average HDD has 
600Mbps controller-to-platters. SATA has usually 3Gbps (sure, SATA1 has 
1.5Gbps).

When I was looking on whole chain (DVB-myth-OS-HDD) bottleneck was 
random write to HDD.
With NCQ I had IOwait about 45-55% with 16HD streams, VERY rough 
estimation means something like 30-32HD streams is limit.
Having better random write optimization that 32 stages NCQ will help to 
get more.
> I have a UPS but I have also pulled the wrong drive from the hot swap array! The XFS tools are different so you must learn them.
This is another argument for EXT4 over XFS - albeit subjective one :-)
>> 4.stability/maturity (i.e. recovery from bad/deep FS corruption);
> As above, learn the tools, ask the mailing lists but it’s worked well for me for many years.
Here i think EXT4 is better choice. It is default in many distros so 
probably most tested and verified....
>
>> 5.any other I forgot..
> A friend runs a simultaneous recorder system (he uses MythTV for this) where he records all the main UK DVBT channels HD & SD from seven tuners on to six harddrives, he says ext4 is useless for this but xfs works fine.
This is VERY interesting info. Is Your friend investigate why EXt4 goes 
so badly?
Wasn't his EXT4 issue related to use-case where FS is asked to write and 
delete in real-time on the same time?
it will be good to understand this!
Why he goes with XFS and not with JFS?