[mythtv-users] Any way to tell which tuner card might be bad?

[R. G. Newbury]

On 02/10/2010 05:35 PM, James Pifer wrote:
>> Well that doesn't tell us anything *bad*, which is *good*. Lots of
>> working space, and all on one drive. As a previous post pointed out,
>> heavy mysql AND video accesses at the same time, can cause problems. I
>> suspect we are down to something like that, since the hardware seems to
>> be good.
>> So we have cut off some corner cases....which leaves us in the
>> featureless middle!
>>
>> Geoff
>>
>>
>
> I appreciate the help. I'm going to see what happens. I've been wanting
> to upgrade the hardware for quite some time, so maybe this will be my
> opportunity.
>
> So it would be best to have a separate hard drive just for your
> recordings, correct? If I had a smaller hard drive for the OS/mysql and
> a large dedicated drive for video/recording storage, theoretically that
> would/could fix the IOBOUND issue?

Theoretically. But of course, in theory, theory and practice are equal, 
but in practice, they are not.

> Of course it's not 100% that this is what is causing the issues on the
> recordings, but it very well could be and IOBOUND errors are not good
> either way...

I've posted my thoughts about this before. The OS drive can be quite 
small and there are many reasons why it should be separated from the 
data storage drive(s). Splitting mysql database reads/writes from video 
file reads/writes lowers the stress on the harddrives and allows for 
particular speed strategies on the drives themselves (noatime, 
nodiratime etc etc.)

Since it can be small, I am seriously considering using a 16G OCZ eSata 
Throttle SSD stick for my next upgrade to the box. The Throttle has a 
eSata port on one end and USB on the other for power. 16G for $30, 32G 
for $60 at present.
I have run the box directly from a USB stick, but it was slow to react. 
I suspect that was because of it being USB.

The OS drive presently has 6 partitions: /, /boot, /home, /keep, 
/usr/local and /var. I don't really need /keep or /boot. (This desktop 
no longer has a /boot as fedora12 can now use ext4 for /boot). Total 
used is about 12G from memory. /home is a primary, and on the next setup 
will be the first primary partition with a known number of sectors. 
(Worst case scenario is to use dd to recover those sectors.) The mythbox 
has 2Gig of ram and I have never seen it use over about 1.2G. I have no 
swap partition and have never used one on the mythbox going back to 
Fedora 4/5 days

/tmp is a symlink to /var/tmp/tmp, putting all of the 'runaway error 
messages' on one partition. The system stops working properly and 
becomes unresponsive but does not crash when that happens. You can ssh 
in and nuke some files to restore things. ( If you want to test that, do 
a 'cat /dev/video0 > /var/tmp/junk.ts' and let it run for a while with a 
channel tuned in!)

As part of the 'make is safe' structure, (on fedora) I have 
/var/lib/mysql and /var/www/html as symlinks to folders in /home, so 
they do not get affected if things go bad with /var.  (/var/www/html is 
the apache doc_root in RHEL/Centos/Fedora; used by mythweb).

A cron does a mysqlbackup early every morning, of /home and /usr/local 
to /video/temp which is, of course, on the other drive. That also 
captures the /home/mysql/mythconverg database and all of the programs 
under /usr/local/bin, /usr/local/lib and my own scripts in 
/usr/local/sbin. I also keep backups of /etc there. Everything I would 
need for a restore is backed up there (and whenever I remember to do so, 
onto a USB stick!).

Of course, separating things like this allows transparent expansion of 
the storage, or setting up raid arrays, without affecting myth in the 
slightest: just add folders to the Default Storage group and amend 
/etc/fstab as necessary to mount things.

The OS drive uses ext4. It's alleged delete problems with large files do 
not affect an OS drive. The storage drive uses xfs with allocsize=512M 
to reduce fragmentation.

Now that I've given the lecture, where do I send the invoice?

Geoff



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