SSD Lifetime

[ewx]

Someone asked how long I expected my SSDs to last. The context was swapping to SSD, but obviously it actually depends on the usage pattern as a whole, not just one aspect of it. Here’s the SMART attribute data for an Intel SSD that’s been in constant light usage, including swapping, for the last 18 months:

smartctl 5.40 2010-07-12 r3124 [i686-pc-linux-gnu] (local build)
Copyright (C) 2002-10 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF READ SMART DATA SECTION ===
SMART Attributes Data Structure revision number: 5
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  3 Spin_Up_Time            0x0020   100   100   000    Old_age   Offline      -       0
  4 Start_Stop_Count        0x0030   100   100   000    Old_age   Offline      -       0
  5 Reallocated_Sector_Ct   0x0032   100   100   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   100   100   000    Old_age   Always       -       12131
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       19
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       5
225 Load_Cycle_Count        0x0030   200   200   000    Old_age   Offline      -       9248
226 Load-in_Time            0x0032   100   100   000    Old_age   Always       -       16301
227 Torq-amp_Count          0x0032   100   100   000    Old_age   Always       -       1
228 Power-off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       1018723636
232 Available_Reservd_Space 0x0033   100   100   010    Pre-fail  Always       -       0
233 Media_Wearout_Indicator 0x0032   099   099   000    Old_age   Always       -       0
184 End-to-End_Error        0x0033   100   100   099    Pre-fail  Always       -       0

A couple of caveats about interpretation. Firstly, TYPE is the type of the attribute, not a commentary on its current value - i.e. the ones that say Old_age will still say that on a brand new device and Pre-fail doesn’t mean a failure is imminent. Secondly high VALUE fields are better: they mostly start at a high value (here, mostly 100) and decline as things get worse.

Anyway Media_Wearout_Indicator is the one of interest here. Intel describe this as follows:

The E9 SMART attribute reports a normalized value of 100 (when the SSD is brand new out of the factory) and declines to a minimum value of 1.

The normalized value decreases as the NAND erase cycles increase from 0 to the maximum-rated cycles. Once the normalized value reaches 1, the number will not decrease, although it is likely that additional wear can be put on the device.

So the current value means the device has performed at least 1% and less than 2% of the maximum rated erase cycles; if current usage patterns persist it’d take between 75 and 150 years to reach the maximum.

Obviously this isn’t the whole story. The device only has a three year warranty, and plenty of other things could go wrong either with the disk or the computer containing it; and Intel could have got their sums wrong. Nevertheless I’m pretty comfortable that flash wear is not going to be a problem in the near future.

• Intel SSD 330 series product specification - see s5.0 for SMART attributes
• Monitoring Media Wearout Levels of Intel Solid-State Drives
• SandForce SMART attributes - SSD_Life_Left seems to be the nearest equivalent of Media_Wearout_Indicator.
• Wikipedia page on SMART
• smartmontools

Comments

[ewx.livejournal.com]

Nominally 40GB (in practice about 38GB), around 8GB used.