[mythtv-users] Can't get storage priorities correctly.

[James Linder]

> On Nov 18, 2023, at 18:17, Stephen Worthington <stephen_agent at jsw.gen.nz> wrote:
> 
> On Fri, 17 Nov 2023 22:06:02 -0600, you wrote:
> 
>> Thanks for your concern. I thought a  lot before choosing this path.
>> 
>> 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.
> 
> That certainly sounds good.  But do check the smartctl -a output - my
> new 1 Tbyte SSD in my main MythTV box is only 214 days old, and is
> currently showing 16.1 TBytes written without me doing any recording
> to it (75 Gbytes per day).  It says it is 1% used, so it is still
> going to last a long time, even at that rate.
> 
>> 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.
> 
> Over the last 10 years I think I will have had 10+ hard drives die
> also, but only 2 of them prematurely.  The others had been running for
> a long time, over their expected lifetime.  I now am buying enterprise
> class drives (20+ Tbytes) with 5 year warranties, but they have not
> been around for more than 5 years yet.  I do have two ancient
> enterprise class 3 Tbyte HGST drives that I swapped out because they
> were too small after 9-10 years 24/7.  I put one of them into my
> mother's MythTV box running 24/7 again a couple of months later.  It
> is currently showing 105553 power on hours (12 years) and is showing
> no problems at all.  They were not cheap when I bought them, but they
> do show that enterprise class drives can last a very long time.
> 
>> Suppose I am wrong and my SSDs show wear, it is a single mythtv-setup 
>> change that will get back to trashing spinning disks.
> 
> Yes, very easy to do.  I really like how storage groups work.
> 
>> 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.
> 
> With my enterprise class drives, I can have them recording 2
> programmes at once and playing back at the same time with no problems.
> From the specifications, I would think three recordings at once would
> be fine too, but I never get to that as I have 7 recording drives.  I
> can certainly hear them seeking, but it does not sound over the top at
> all.  But I can also do 2 recordings plus playback from my old (very
> quiet) WD Green 4 Tbyte drives, which have much lower specifications.
> They are currently showing 81029 and 77591 power on hours (9.2 and 8.9
> years).  So even cheap drives can last well if you get lucky and they
> were over designed.
> 
> I am wondering if RAID 1 is the problem somehow.  If the data was
> being written to the first drive and then read back again to be copied
> to the second drive, that might cause what you are getting.  But that
> would be a really bad way of doing RAID 1 when you can just write to
> both drives at once from the same buffers.

Just adding $0.02
I bought 4 WD Passport 4T spinning rust, 2 have failed in 3 years my ONLY SSD failure was an early 64G with very low TBW and smartmon showed it getting old.
James