[mythtv-users] my experience with myth on a solid state drive

Mark J. Small msmall at eastlink.ca
Thu Jan 5 18:49:56 UTC 2012


On January 5, 2012, Ronald Frazier wrote:
> A few months ago, I got a new larger SSD drive for my desktop
> computer, to replace the older, smaller SSD I had previously (a 1st
> generation Intel 80GB). I then decided to take that old drive and use
> that as the primary drive for my myth system. Wow, what an incredible
> performance boost it has been.
> 
> In my experience, myth's program guide has never really been snappy,
> but it seems to have gotten worse over time. Perhaps it's just because
> I've upgraded to digital HD and have about 3 times as many channels as
> I used to. Whatever the cause, it's been a pain to use, sometime even
> taking several seconds to scroll down a page. Likewise, entering the
> Watch Recordings screen seems like it has gotten worse. Again, maybe
> it's just because I have a lot more recordings now than I did several
> years ago. Same thing for Videos.
> 
> Once installing the SSD, the performance of myth is just incredible.
> The program guide is instant...far and away it's the most responsive
> program guide I have ever used, anywhere on any device. Going into the
> Watch Recordings and the Videos screens are likewise nearly instant.
> Mythweb (which has always been slow all around) is likewise incredibly
> fast in all respects...especially the guide. Changing channels in
> LiveTV even seemed quite a bit faster. This was easily one of the best
> upgrades I've done to my myth system over the years.
> 
> Before I made the switch, I did a lot of reading about SSD drives in
> linux, and people talking about putting /tmp or /var or this or that
> onto a physical drive or a tmpfs. The reasoning for all of this is
> that SSDs wear out from excessive writing (unlike HDDs). I figured I'd
> ignore all of that advice and just give it a shot with everything all
> on the SSD (except for my recordings/movies, of course). The only
> thing particular I did was to pay attention to partition
> alignment...some resources said to align it to 512K boundaries, other
> said 1MB boundaries. I played it safe and aligned it to 1MB.
> 
> The intel drives are rated for at least 5 years of 20GB/day of writes.
> You can check the current wear level using the SMART feature of the
> drive. After using this drive in my Windows box for over 3 years, the
> drive still had 93% of it's rated life remaining, so I should have at
> least 4 years of life at 20GB/day. So I began running my system and
> periodically monitoring the wear level. Immediately I discovered I was
> writing about 30+GB/day, which meant the drive would only last about 3
> years. So off I went trying to figure out what was doing so much
> writing. Was it mysql, or logging, or the fact that I'm also running
> my 2 frontend systems (which are diskless boots) from this drive, or
> /tmp? So I began systematically moving things one by one to another
> partition, watching it for a few days, and then moving back when I saw
> no change. Finally when I got to moving /tmp, that made all the
> difference. SSD writes dropped down to about 2GB/day, which means it
> would take 40 years to use up the drive's rated write life.
> 
> So what was doing all the writes to /tmp? Several times an hour, myth
> recalculates its schedule. When it does, it uses about 500MB of
> temporary mysql tables. That alone was responsible for over 90% of the
> writes on the SSD. So instead, I created /tmp as a tmpfs partition.
> I've got 2GB of ram, so that gives /tmp up to 1GB to use.
> 
> So far that's worked just fine with just that one change. I never had
> to mess with all of the other things people say to do to minimize
> wear, like alter the io scheduler or the cache flush timings, or move
> /var or /var/log.

So, which filesystem would you recommend using with an SSD for a myth 
boot/database drive?  I haven't really kept up.

Mark


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