Here are some stats for one of the SSDs which we use at work. The most valuable S.M.A.R.T. attribute which we focus on here is the “Host_Writes_32MiB” which shows what capacity the SSD has written in its lifetime. This is the most important indicator because SSD drives have a limited total Program/Erase cycles (P/E cycles) they can sustain over the life of the flash memory, before they start to fail. According to Wikipedia, the number of those cycles is as follows:

• Single-level cell (SLC) flash, designed for higher performance and longer endurance, can typically operate between 50,000 and 100,000 cycles.
• As of 2011, multi-level cell (MLC) flash is designed for lower cost applications and has a greatly reduced cycle count of typically between 3,000 and 5,000.

Those numbers refer to the internal rewrites of the flash cells at the hardware level. If a cell is 32 MiB and we do a 3200 MiB write transfer from a computer, the actual write cycles of the flash cells in the SSD internally may be higher than 100, because of the complicated internal storage processes inside the SSD. You can review the “Logged S.M.A.R.T. Data” chart in this example.

Another thing to mention before we get to the actual statistics is that the “Power_On_Hours” S.M.A.R.T. attribute is correctly accounted and 100% matches the actual work time span of this SSD drive.

This sample SSD has the following S.M.A.R.T. attributes:

• Host_Writes_32MiB: 3681999
• Power_On_Hours: 41204

We used 40680 power-on-hours in our calculations, because the SSD was “on” a few days before we started using it in production.

Here are the aggregated statistics:

• SSD model: Intel SSD X25-M
• Flash architecture: multi-level cell (MLC)
• Capacity: 80 GB
• In 24/7 service: 1695 days (4+ years)
• Avg. writes: 69.5 GB / day
• Complete device rewrites: 1472
• Read-to-write ratio: 5

The device is still in use and working properly.
Good deal for the buck, Intel SSD!

Update: An Intel 320 Series SSD statistics case

It struck me that we have another SSD which gets a lot more writes.

This sample SSD has the following S.M.A.R.T. attributes:

• Host_Writes_32MiB: 13627899
• Host_Reads_32MiB: 1086459
• Power_On_Hours: 24525

Here are the aggregated statistics:

• SSD model: Intel 320 Series
• Flash architecture: multi-level cell (MLC)
• Capacity: 120 GB
• In 24/7 service: 1021 days (2+ years)
• Avg. writes: 426.8 GB / day
• Complete device rewrites: 3634
• Read-to-write ratio: 0.08

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