What types of SSDs to use.....

[Miroslav Lachman]

Willem Jan Withagen wrote:
> Hi,
>
> I'm looking for advise and suggestions on what SSDs to use for the
> ZFS-systems I have and/or am building....
>
> I know the difference between SLC en MLC , but beyond that I have not
> the best experience with all the older SSD I have lingering about here.
>
> Most of them just "disconnect" after a while.
> It could be because they have exceeded their wear level and just can not
> write any more.  But than that has occurred rather fast.

If we are talking about cheap SSDs... we are using Samsung 840 Pro 
(MLC). We have them on MariaDB (MySQL) server for a few month.

It is good to watch SMART of SSDs, mainly for Wear_Leveling_Count. You 
can see this (for example):

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   099   099   000    Old_age 
Always       -       2176
  12 Power_Cycle_Count       0x0032   099   099   000    Old_age 
Always       -       5
177 Wear_Leveling_Count     0x0013   097   097   000    Pre-fail  Always 
       -       108
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 Uncorrectable_Error_Cnt 0x0032   100   100   000    Old_age   Always 
       -       0
190 Airflow_Temperature_Cel 0x0032   081   069   000    Old_age   Always 
       -       19
195 ECC_Error_Rate          0x001a   200   200   000    Old_age   Always 
       -       0
199 CRC_Error_Count         0x003e   100   100   000    Old_age   Always 
       -       0
235 POR_Recovery_Count      0x0012   099   099   000    Old_age   Always 
       -       2
241 Total_LBAs_Written      0x0032   099   099   000    Old_age   Always 
       -       10494506165

Miroslav Lachman