The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →OpenZFS’s technical king of SLOG devices is Intel Optane (3D XPoint), especially the DC P4800X, P4801X and P1600X. Optane offered exceptionally low latency and high write endurance, but Intel wound down the Optane business in 2022 and these drives are no longer manufactured. For a new system, the practical answer is an enterprise NAND SSD with documented power-loss protection (PLP), chosen for your synchronous-write workload and server platform—not a universal currently sold winner.
First: do you need a SLOG?
A SLOG is a separate device for ZFS’s intent log (ZIL). Every ZFS pool has a ZIL for recording synchronous writes before ZFS acknowledges them as safely stored. A separate log vdev moves that log activity away from the main pool devices.
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A SLOG is not a general-purpose write cache. OpenZFS states, “A SLOG is not a write cache.” Asynchronous writes do not use it, and “If your workload has no synchronous writes, a SLOG changes nothing.” The strongest candidates are sync-heavy NFS servers, databases and virtual-machine hosts.
Check synchronization before buying
- Identify whether the workload issues synchronous writes.
- Check dataset and share settings, application behavior and hypervisor storage policy.
- Measure or estimate sustained synchronous-write throughput and latency.
- Do not set
sync=disabledas a casual speed fix: OpenZFS documents that setting as skipping the ZIL at the cost of recent-write durability.
Why Optane remains the performance reference
OpenZFS describes Optane/3D XPoint SSDs as having substantially better latency and write endurance than NAND flash and says enterprise Optane models make excellent SLOG devices. Its named models known to perform well are:
#1 Best Overall
| Model | Status | Why it appears in SLOG guidance |
|---|---|---|
| Intel Optane DC P4800X | Discontinued; legacy sourcing only | Optane latency and endurance characteristics |
| Intel Optane DC P4801X | Discontinued; legacy sourcing only | Optane latency and endurance characteristics |
| Intel Optane DC P1600X | Discontinued; legacy or used sourcing only | Optane latency and endurance characteristics |
This is a technical preference, not proof of current retail availability, price, warranty coverage or a 2026 cross-vendor benchmark victory. Used Optane can also introduce unknown wear, firmware history and seller-authenticity risks. Treat these models as specialist legacy options and verify condition before deployment.
The best practical choice for a new build
For new systems, OpenZFS points to enterprise NAND flash with power-failure protection as the practical alternative. Its non-exhaustive examples include Micron 7300, 7400 and 7450 PRO/MAX, Kingston DC1000B, Samsung PM963 and PM1725 series, and Intel DC P3500, P3600 and P3700 series.
Those names are examples, not a current compatibility list or a guarantee that every capacity and revision has identical protection. Confirm the exact SKU, firmware and manufacturer PLP specification. Consumer SSDs that merely advertise “power safe” behavior should not be treated as equivalent to a drive with clearly documented enterprise PLP.
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Rank #2
- 1B Storage Capacity
- M2. 2280 Form Factor
- PCIe NVMe 3.0 x4 Interface
- 1800 MB/s Sequential Read Speeds. 1800 Sequential Write Speeds. Intel QLC 3D NAND
How to compare SLOG devices
1. Workload fit
Buy for synchronous writes, not for headline sequential speed. A fast drive provides no benefit to a workload that never waits for synchronous commits.
2. Latency and sustained synchronous-write throughput
TrueNAS identifies latency and write endurance as primary SLOG concerns. The log device’s sustained synchronous-write capability should exceed the workload’s planned synchronous-write rate. Short benchmark bursts are not a substitute for steady-state behavior.
3. Power-loss protection
The drive must preserve flushed data and its own metadata when power fails. OpenZFS’s documented guarantee does not require the SSD to preserve data that had not been flushed. Hardware PLP is preferred when you want stronger protection against firmware bugs; manufacturer firmware-based protection claims require careful validation.
Rank #3
- Snappy PC experience with short boot times, fast application launches, extraordinary gaming experience and responsive browsing
- Pair Intel Optane memory with storage media (HDD, SSD), to get amazing performance and responsiveness without compromising storage capacities
- Supported on 7th Gen Intel Corei3 processor and above
- Requires Optane Ready Motherboard and storage drive such as HDD and/or SSD
- A computer with Intel Optane memory adapts to your everyday computing activities to make your repetitive tasks increasingly faster, smoother and easier to accomplish
4. Endurance
SLOG traffic can be persistent and write-intensive. Estimate daily log writes, write amplification and the intended service life, then compare those figures with the drive’s endurance rating. TrueNAS lists endurance as a primary selection criterion.
5. Capacity and over-provisioning
Do not assume a larger SLOG is automatically faster. OpenZFS says SLOG devices rarely have more than about 4 GB in use at a time and notes that useful size depends on writes between transaction-group commits and ARC limits. It also says useful SLOG size should not exceed the maximum ARC size.
For NAND, OpenZFS suggests over-provisioning spare area and says about 4 GB is sufficient in many configurations, while calling that figure somewhat arbitrary and workload-dependent. TrueNAS project guidance separately recommends a 16 GB over-provisioned device for typical HDD-pool performance characteristics. These are different contexts, not a universal size rule.
Rank #4
- OEM PRODUCT, NO PACKAGING.
6. Redundancy and failure policy
A failed log device can cause performance degradation and, depending on failure timing and pool state, increase data-loss risk. TrueNAS says a log vdev may be mirrored. OpenZFS supports multiple log devices and mirroring, but raidz is not supported for the intent log. Decide whether the workload justifies mirrored SLOG devices and budget for matched, PLP-capable drives.
7. Physical and platform compatibility
- Match the interface and form factor to the server, backplane and HBA.
- Check that the operating system and platform expose the device correctly.
- Verify firmware versions and vendor support.
- Provide adequate airflow: OpenZFS notes that some NVMe devices can throttle severely or develop reliability problems when overheated.
A practical selection path
- Confirm synchronous I/O. If the workload is asynchronous, stop: a SLOG will not help.
- Set a performance target. Record expected sustained synchronous-write throughput and acceptable commit latency.
- Shortlist enterprise drives. Require explicit PLP documentation and an endurance rating appropriate to the write load.
- Validate the exact SKU. Capacity, NAND type, firmware and PLP implementation can differ within one product family.
- Choose size deliberately. Use workload and platform guidance; do not equate capacity with cache size.
- Decide on mirroring. Use mirrored log devices when the application’s durability and availability requirements justify the additional drive.
- Test under sustained load and temperature. Confirm latency, throughput, SMART/NVMe health data and thermal behavior before placing the device in production.
What “current king” means in 2026
There is no documented universal 2026 market winner in the available official guidance. Optane remains the performance benchmark in OpenZFS’s technical description, but it is discontinued. Current systems therefore need a reasoned enterprise-NAND choice based on PLP, latency, endurance, sustained synchronous-write performance, size, redundancy and platform fit.
In short: an authentic, healthy Optane P4800X, P4801X or P1600X can still be an outstanding legacy SLOG where it is properly sourced and supported. For a fresh build, select an enterprise NAND SSD with verified PLP and workload-appropriate endurance rather than chasing a discontinued product or treating a consumer NVMe drive as an equivalent substitute.
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