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TBW from SSDs with S.M.A.R.T Values in ESXi

  • May 23, 2016
  • 5 min read
Online Marketing Manager at StarWind. In touch with virtualization world, may know stuff you are interested in.
Online Marketing Manager at StarWind. In touch with virtualization world, may know stuff you are interested in.

Solid-State-Drives are becoming widely implemented in ESXi hosts for caching (vFlash Read Cache, PernixData FVP), Virtual SAN or plain Datastores. Unfortunately, SSDs have  limited lifetime per cell. Its value may range from 1.000 times in consumer TLC SSDs up to 100.000 times in enterprise SLC based SSDs. Lifetime can be estimated by device TBW parameters provided by vendor in its specification, It describes how many Terabytes can be written to the entire device, until the warranty expires.smartctl_in_esxi

As VMWare does not provide convenient and easy way to read RAW S.M.A.R.T values on ESXi hosts, a ported version of smartctl has been created, which is part of smartmontools to ESXi.

Below there is an example of an ESXi Host report without smartctl. The device analyzed is a Samsung SSD 850 EVO M.2 250GB used as a local Datastore. Warranty for this SSD is 75TBW.

ESXCLI can display S.M.A.R.T stats with
esxcli storage core device smart get -d [device]

The next table shows the stats provided by ESXCLI, which are a bit more verbose.

ESXi keeps track of all read and write operations to the disk, but the counters get reset when ESXi is rebooted.

And here is the report by smartctl:

In the SMART Attributes section, there is a Total_LBAs_Written value (ID #241). In order to get Terabytes, we need to multiply this value with the sector size (512 bytes) and divide by 1099511627776 (1024^4).

                                                Total_LBAs_Written * Sector Size / 1024^4 = TBW

                                      6343034492 * 512 / 1099511627776 = 2.95 TBW

That gives us 3 of 75 TBW. Taking into consideration the parameter Power_On_Hours (SMART ID #9), which tells us that the device has been in use for about 200 days, we may prognose that this SSD will last for the next 13 years.

The smartctl can be obtained from here:

Note: The use of this VIB is totally unsupported, proceed at your own risk. Tested with ESXi only.

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Dmytro Malynka
Dmytro Malynka StarWind Virtual SAN Product Manager
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