[mythtv-users] mythtv-users Digest, Vol 204, Issue 32

[Stephen Worthington]

On Mon, 23 Mar 2020 20:45:35 +0800, you wrote:

>> Doing that should allow you to record more programmes at the same
>> time.  However, it also will use a *lot* more of the write endurance
>> of the SSD.  So you will need to calculate how many more "terabytes
>> written" it will use and see if the SSD's lifetime will allow you to
>> use it that way.  It very likely will, but only if you intend to
>> upgrade the box to a new SSD in 5 years or so.
>> *************************
>
>
>Simon there seems to be a lot of myth. (sic) on the subject
>
>=== START OF INFORMATION SECTION ===
>Device Model:     Samsung SSD 860 QVO 2TB
>Serial Number:    S4CYNF0M302546M
>LU WWN Device Id: 5 002538 e40e4fcfb
>Firmware Version: RVQ01B6Q
>User Capacity:    2,000,398,934,016 bytes [2.00 TB]
>Sector Size:      512 bytes logical/physical
>Rotation Rate:    Solid State Device
>Form Factor:      2.5 inches
>Device is:        Not in smartctl database [for details use: -P showall]
>ATA Version is:   ACS-4 T13/BSR INCITS 529 revision 5
>SATA Version is:  SATA 3.2, 6.0 Gb/s (current: 6.0 Gb/s)
>Local Time is:    Mon Mar 23 20:14:07 2020 AWST
>SMART support is: Available - device has SMART capability.
>SMART support is: Enabled
>
>...
>
>SMART Attributes Data Structure revision number: 1
>Vendor Specific SMART Attributes with Thresholds:
>ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
>  5 Reallocated_Sector_Ct   0x0033   100   100   010    Pre-fail  Always       -       0
>  9 Power_On_Hours          0x0032   098   098   000    Old_age   Always       -       5376
> 12 Power_Cycle_Count       0x0032   099   099   000    Old_age   Always       -       34
>177 Wear_Leveling_Count     0x0013   099   099   000    Pre-fail  Always       -       3
>179 Used_Rsvd_Blk_Cnt_Tot   0x0013   100   100   010    Pre-fail  Always       -       0
>181 Program_Fail_Cnt_Total  0x0032   100   100   010    Old_age   Always       -       0
>182 Erase_Fail_Count_Total  0x0032   100   100   010    Old_age   Always       -       0
>183 Runtime_Bad_Block       0x0013   100   100   010    Pre-fail  Always       -       0
>187 Reported_Uncorrect      0x0032   100   100   000    Old_age   Always       -       0
>190 Airflow_Temperature_Cel 0x0032   061   044   000    Old_age   Always       -       39
>195 Hardware_ECC_Recovered  0x001a   200   200   000    Old_age   Always       -       0
>199 UDMA_CRC_Error_Count    0x003e   100   100   000    Old_age   Always       -       0
>235 Unknown_Attribute       0x0012   099   099   000    Old_age   Always       -       23
>241 Total_LBAs_Written      0x0032   099   099   000    Old_age   Always       -       9162621562
>
>I record about 5 hours per day.
>1/2 year of 24/7 give me a life if 150 years projected
>
>If you read pros-n-cons the concensus is a cron job once a day (heck once a week)
>
>[sandypit] /store/jam [1005]% cat /etc/cron.weekly/trim
>/sbin/fstrim /
>/sbin/fstrim /store
>
>James

The Samsung SSD 860 QVO 2TB has a specified endurance of 720 Tbytes
written.  At 5 hours per day if that was all HD recordings, that is
likely about say 20 Gbytes per day.  So that would give a lifetime of
36,000 days or over 98 years.  Not a problem!  It looks like the
endurances have increased a fair bit since I last did that
calculation.  A major part of the increased endurance though is simply
the much larger size of SSDs now.  The 1TB version of that SSD has
half the endurance.

The timing of running fstrim depends a great deal on how full you have
your SSD.  If it is near full, then you need to trim often.  If there
is lots of free space, then you only need to trim when you have
written almost as much data as there is free space.

BTW If I am interpreting your Power_On_Hours and Total_LBAs_Written
correctly, you are using about 20.9 Gbytes Written per day.  So your
expected lifetime is going to be a little less than 98 years.