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

[Andre Newman]

On 30 Jun 2015, at 15:06, Henk D. Schoneveld <belcampo at zonnet.nl> wrote:

> 
> On 30 Jun 2015, at 14:20, Andre Newman <mythtv-list at dinkum.org.uk> wrote:
> 
>> 
>> On 30 Jun 2015, at 09:47, Warpme <warpme at o2.pl> wrote:
>> 
>>> Hi *
>>> 
>>> I just got some free space on my server (8T Seagate Archive for videos) which temporarily gives me spare capacity allowing change filesystem for recordings volumes.
>> 
>> 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. 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.
>> 
>>> 
>>> Currently I have 2x4T HDD allocated purely for recordings. Both volumes are now on ext3.
>>> 
>>> After years of relaying on ext3 I think it is not best filesystem for recordings as:
>>> -delete is very throughput expensive
>>> -chkdsk is really long
>>> -starting loosless cut makes hell of:
>>> TFW(/myth/tv/21101_20150630054000.ts:67): write(57152) cnt 35 total 2079656 -- took a long time, 2571 ms
>>> 
>>> So what FS will be better: XFS or JFS or …?
>> 
>> 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.
>> 
>> 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.
> Using the allocsize=1G or even higher, with this option of xfs you should be able to minimise/exclude that problem. 

Oops sorry forgot to mention that detail, it helps a lot on any drive but the AV drives still seem to seek less, with the same settings.

e.g.

/dev/disk/by-label/MythR1	/var/lib/mythtv/R1	xfs	defaults,noatime,nodiratime,allocsize=512m	0	0



>> 
>> 
>>> 
>>> I think following criteria should be compared:
>>> 1.concurrency (frequently I have 8-10 concurrent HD recordings);
>> This is a lot of simultaneous HD for only two drives! I usually think 4 per drive is absolute max, pref  3.
>> 
>> I am recording 6 HD channels simultaneously+ overlaps on to one XFS 4TB Seagate Pipeline drive for an experiment, there are dropouts around overlaps and sometimes in programmes but this is not using MythTV, I think Myth is much more demanding on drive and FS performance. This drive is always full due to the permanent recordings (6pm to 1am every day) so a delete oldest job runs to clear space, I don’t think this would be possible with ext4 or 3.
>> 
>>> 2.CPU consumption under high FS load;
>> I see xfs being higher than ext4 but it seems to cause less packets drops from my tuner cards, the HVR4000’s lose interrupts easily when CPU load is high, lost ints= lost dvb packets.
>> 
>>> 3.reliability (I don't have UPS and sometimes power is lost when many recordings are ongoing);
>> 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 but I have found them able to recover from many external problems, hot swap mistakes, kernel AHCI driver problems, bad cables, failed fans.
>>> 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.
>> 
>>> 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. His system is expiring and deleting files during recordings all the time, he had problems with four drives, upgraded to five, then added the UK HD channels and added a sixth drive.
>> 
>> Andre 
>> 
>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
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>> 
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