<html><br />On Wednesday, November 22, 2017 19:01 CET, Keith Pyle <kpyle@austin.rr.com> wrote:<br /> <blockquote type="cite" cite="f2da626e-d5ec-73da-f917-7c86371803bc@austin.rr.com">On 11/22/17 08:17, Marius Schrecker wrote:<br />> ? I am repurposing an old, box that was previously used as a combined mythtv backend/frontend, Logitech Media Server and nfs fileserver as a mythtv backend only.<br />><br />> The system has a maximum of 8GB RAM, a quite well used 120GB SSD (no signs of failure yet) and I just replaced the 3TB media storage spindle drive with a new 4TB unit.<br />><br />> My main concern is offloading the SSD as much as possible to prolong its life.<br /><br />Marius,<br /><br />Mike's comments are quite correct. Look in your smartctl output for a<br />line similar to this:<br /><br />ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE<br />UPDATED WHEN_FAILED RAW_VALUE<br /><br />233 Media_Wearout_Indicator 0x0032 098 098 000 Old_age<br />Always - 0<br /><br />Many SSD's include this metric as an indicator of how much wear leveling<br />has been done (strictly speaking, it's a NAND erase cycle metric).<br />Intel defined this metric for their SSD's, but I've seen it on non-Intel<br />drives too. A new drive should show a value of 100. A value of 1<br />means the drive has reached its designed write cycle limit, but it may<br />well continue working past that point. The value is a linear function<br />of the write/erase cycle count.<br /><br />The line above is for an 80 GB Intel MLC SSD that has 72000 hours of use<br />(8 years) in my Myth backend as the OS and DB drive. It shows total<br />writes of just under 7 TB. It was at ~62000 hours of use that it<br />dropped from 99 to 98. So, for a pure backend, a decent SSD will work<br />fine for a very long time. It may well die due to other failures long<br />before reaching a write limit. For my backend workload, this drive's<br />flash should have another 300+ years. :-)<br /><br />With regard to memory, Linux will happily use whatever you provide for<br />caching. The right amount of caching is highly dependent on what you<br />run. If your workload involves frequently reading the same data many<br />times, you'll benefit from having enough memory to keep that frequently<br />accessed data in cache. For a Myth backend that runs commflag jobs, it<br />can help to have the video data still in memory rather than re-reading<br />it from disk.<br /><br />My backend runs Myth, mysql, and apache. It has 4 GB and typically has<br />1.0-1.5 GB in the "used" category. That leaves 2.5-3.0 GB being used<br />for cache and I don't see any signs of the system being resource stressed.<br /><br />Keith<br /> </blockquote>Thanks Keith,<br /><br /> My drive doesn't seem to display that metric, but one or two others seem to suggest that there'e plenty of life left. Here's the table again:<br /><span id="messageContent">ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE<br /> 1 Raw_Read_Error_Rate 0x0033 120 120 050 Pre-fail Always - 0/0<br /> 5 Retired_Block_Count 0x0033 100 100 003 Pre-fail Always - 0<br /> 9 Power_On_Hours_and_Msec 0x0032 084 084 000 Old_age Always - 14095h+59m+25.710s<br /> 12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 103<br />171 Program_Fail_Count 0x000a 000 000 000 Old_age Always - 0<br />172 Erase_Fail_Count 0x0032 000 000 000 Old_age Always - 0<br />174 Unexpect_Power_Loss_Ct 0x0030 000 000 000 Old_age Offline - 37<br />177 Wear_Range_Delta 0x0000 000 000 000 Old_age Offline - 1<br />181 Program_Fail_Count 0x000a 000 000 000 Old_age Always - 0<br />182 Erase_Fail_Count 0x0032 000 000 000 Old_age Always - 0<br />187 Reported_Uncorrect 0x0012 100 100 000 Old_age Always - 0<br />189 Airflow_Temperature_Cel 0x0000 017 043 000 Old_age Offline - 17 (Min/Max 8/43)<br />194 Temperature_Celsius 0x0022 017 043 000 Old_age Always - 17 (Min/Max 8/43)<br />195 ECC_Uncorr_Error_Count 0x001c 120 120 000 Old_age Offline - 0/0<br />196 Reallocated_Event_Count 0x0033 100 100 003 Pre-fail Always - 0<br />201 Unc_Soft_Read_Err_Rate 0x001c 120 120 000 Old_age Offline - 0/0<br />204 Soft_ECC_Correct_Rate 0x001c 120 120 000 Old_age Offline - 0/0<br />230 Life_Curve_Status 0x0013 100 100 000 Pre-fail Always - 100<br />231 SSD_Life_Left 0x0013 100 100 010 Pre-fail Always - 0<br />233 SandForce_Internal 0x0032 000 000 000 Old_age Always - 1445<br />234 SandForce_Internal 0x0032 000 000 000 Old_age Always - 729<br />241 Lifetime_Writes_GiB 0x0032 000 000 000 Old_age Always - 729<br />242 Lifetime_Reads_GiB 0x0032 000 000 000 Old_age Always - 189</span><br /><br /><br />BR.<br /><br />-Marius--<br /> </html>