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<div class="moz-cite-prefix">On 11/17/23 21:23, Stephen Worthington
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:afagli1mvnssdth1ul2uahslco2rabf5sm@4ax.com">
<pre class="moz-quote-pre" wrap="">On Fri, 17 Nov 2023 17:35:49 -0600, you wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">On 11/17/23 10:59, Ram Ramesh wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">I have two storage directories of vastly different sizes (1 TB SSD and
10+TB spinning RAID1). I had them both in default group and balancing
algorithm as "combined" with default setting. I thought that myth is
smart and will figure out and favor SSD over spinning disk when
possible. That did not work. So, I changed the algorithm to "Balanced
free percent" and was hoping it will keep about the same % of free
space in both disks. I noticed today that SSD has about 13% (96G) use
(87% (660G) free) and spinning disks have about 94% (12T) use (6%
(770G) free). This means next recording should go to SSD. However, it
is now writing to my spinning disks. What did I do wrong?
Distribution: Debian bookworm (Linux 6.1.10)
Myth: 31+fixes from debian-multimedia
(31.0+fixes20201214.gite9b795a1e4-dmo0~bpo10+1 as per apt)
I only changed the storage priorities yesterday and the new recording
is the first one after that. Do I need to wait or reboot after
changing storage balancing algorithm before it takes effect?
Regards
Ramesh
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">Found the problem. I had not started mythtv-setup with sufficient
privilege to kill the running backend. So, even though it reported that
it stopped backend, it did not. Thus my update did not make it to
backend at all. Once I restarted backend manually, it seem to work as
expected.
I wish backend-setup caught this error and failed instead of making me
believe that everything is fine. Anyway, I am running an older version,
and may be it is fixed already.
Regards
Ramesh
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
Have you done the calculations for the extra usage that MythTV will be
doing for the SSD? When I looked at using an M.2 SSD for recording,
the calculations showed that it would be worn out pretty rapidly, due
to the recording files being large. The lifetime of an SSD is
normally in TBytes written - writing multiple multi-Gbyte files per
day is a good way to wear one out.
Do you have a particular reason for wanting the recordings done on the
SSD? Or is it just that you need to record more things at the same
time than can be done with one hard drive?
You also need to look at the SSD's characteristics. A lot of SSDs
have cache, and when the writes exceed the cache size, they slow down
a lot, until the cache can be written to the actual flash storage in
the SSD. With the large file sizes for recordings, the cache size can
easily be filled, particularly if you are recording more than one
programme at once to the SSD.
So if you are just needing to make more recordings at the same time, I
would recommend investing in another hard drive, rather than using
your SSD. Or do the lifetime calculations and make sure to get a new
SSD as soon as the old one is getting low on lifetime - that may be
every year or two.
And make sure you install smartmontools and use the smartctl command
to see what the lifetime writes are and what the SSD is reporting as
its remaining lifetime or % used or whichever way it reports that. I
have smartctl set up to monitor all my drives (SSD and spinning rust)
and report any problems via email and popup messages. This has saved
me many times when a drive has started to die.
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</pre>
</blockquote>
Thanks for your concern. I thought a lot before choosing this path.
<br>
<br>
Yes, I did my calculations. My SSDs have 600TBW and at 30GB per day,
I am looking at 54 years of life (600*1000/30/365 ~ 54). I also have
smartd doing its thing. It will report when SSDs start using their
spare blocks. At about $60/TB (for 54 years of claimed life), I
feel it is a fair game. <br>
<br>
So far, in my mythtv usage (10+ years), I have had 10+ spinning
disks die. I have still my very first SSD (256G SATA) and several
others as I have no use for them with newer/larger SSDs replacing
the old ones. So, I am looking to try them out to see if TBW values
really happen. <br>
<br>
Suppose I am wrong and my SSDs show wear, it is a single
mythtv-setup change that will get back to trashing spinning disks. <br>
<br>
When I record and watch at the same time, the amount of seek is very
noticeable (especially with RAIDs) and I prefer the random access
capabilities of SSDs.<br>
<br>
Regards<br>
Ramesh<br>
<br>
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