[mythtv-users] mythtv on 2 computers and filenames

[Stephen Worthington]

On Tue, 27 Nov 2018 21:59:07 +1100, you wrote:

>On Mon, Nov 26, 2018 at 06:45:00PM +0000, Simon Hobson wrote:
><snip>
>> Klaus Becker <colonius at free.fr> wrote:
>> 
>> > And I cannot rely the external drive to both machines ?
>> 
>> 
>> Short version: No, you cannot connect the drive to two computers at
>> once - that is a recipe for near instant disaster as they will just
>> trash the filesystem between them - each one will write what it
>> thinks is on the drive, corrupting all the filesystem data
>> structures as they go.
>> 
>> Longer version: Well, you can, but you have to use a filesystem and
>> host setups that is specifically designed for that - the hosts need
>> to co-ordinate between themselves what is going on with the
>> filesystem. It's not something I've done, and it's the sort of thing
>> normally reserved for hosting where the operators want the
>> flexibility of accessing storage from multiple machines (typically
>> a cluster) at once. But in the general case, you can't just connect
>> the drive to two computers at once.
>> 
>
>I hesitate to suggest this but ... NFS?
>Attach the disk to the desktop, export it to the laptop.
>NFS will abitrate the laptop's writes.

Or SMB (SAMBA/CIFS).  Setting up NFS is a bit hard to understand - the
learning curve is steep.

>That said, expecting an external usb-connected disk to be
>reliable for longer than a few days is - optomistic, shall we say?

Where to you get that from?  You must have met the wrong hardware.  I
have a nice USB 3 external drive from WD that has never given me any
problems over the 6? years I have had it, and neither do I have any
problems with any hard drives I mount using my USB 3 external drive
mounts.  Using USB 2 for hard drives was not so good, but that was
just because it was so slow compared to the speed of the drive.  When
Linux started supporting USB 3, there were quite a few problems with
the initial drivers, but that is all gone now.

>And then we add the flakiness of the average home network on top.
>But if the link is 1Gig/s the write speed _could_ be usable;
>depends on how many simultaneous HD streams Klaus wants to record.

Speak for yourself, but my home network is very reliable.  Between
Linux boxes, I get full throughput of 1 Gbit/s Ethernet, with the
right protocol.  But SMB and NFS are not as fast.  Windows is not so
good either, but what to you expect.  But since the fastest hard disks
now have sustained serial write speeds of up to 260 Mbytes/s, 1 Gbit/s
Ethernet it now too slow to support that - you would need over 2
Gbit/s.  So when I can afford it, I am planning to upgrade my network
to at least 10 Gbit/s.  The equipment to do that is coming down in
price nicely now.

But that is all theoretical limits.  In the real world, TV
transmissions over DVB-T2 or DVB-S2 are not going to be higher than
about 10 Mbytes/s for HD programmes.  So that is 80 Mbit/s, and a 1
Gbit/s Ethernet can carry quite a few connections at 80 Mbit/s.

Most of the flakiness in home networks has to do with WiFi, rather
than Ethernet.  Cabled Ethernet connections are very reliable.  You
would never want to do recordings via WiFi.  There are some bad
routers provided by ISPs that also cause problems, but they normally
do not interfere with the Ethernet connections via your Ethernet
switch.  So if you have one of those bad routers, you would be best to
use manual static IP address assignments, so that the router has no
control at all over the box.  That is best practice for any box acting
as a server, such as a MythTV backend box.

>Approach this option with caution
>Vince