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Contact an Enterprise SpecialistTrueNAS CORE Version Documentation
This content follows the TrueNAS CORE 13.0 releases. Use the Product and Version selectors above to view content specific to different TrueNAS software or major version.
SLOG Overprovisioning
2 minute read.
Over-provisioning SLOG SSDs is useful for different scenarios. The most useful benefit of over-provisioning is greatly extending SSD life. Over-provisioning an SSD distributes the total number of writes and erases across more flash blocks on the drive.
Seagate provides a thoughtful investigation into over-provisioning SSDs here: https://www.seagate.com/blog/ssd-over-provisioning-benefits-master-ti/.
Some SATA devices are limited to one resize per power cycle. Some BIOS can block resize during boot and require a live power cycle.
To over provision a SLOG device, log in to TrueNAS and go to System > Advanced. Enter an over-provision value corresponding to the new size in GB in the Log (Write Cache) Overprovision Size in GiB field.
When this value is applied, the over-provision value is applied whenever a pool is created with a SLOG device.
It is impossible to restore an over-provisioned SLOG device back to original capacity without running command disk_resize after first destroying the pool it was part of and issuing a full power cycle.
Only one over-provision/under-provision operation occurs per power cycle.
Erasing the over-provision setting in System > Advanced Log (Write Cache) Overprovision Size in GiB field and setting to none prevents future SLOG devices from being over-provisioned.