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Hardware

2,146 bytes added, 17:30, 6 April 2017
Reorganize flash storage section, add NVMe drives, add disclaimer on vendor neutrality, add criteria for inclusion into list and recommendation that anyone who finds an omission contact the openzfs mailing list.
As of 2014, Solid state storage is dominated by NAND-flash and most articles on solid state storage focus on it exclusively. As of 2014, the most popular form of flash storage used with ZFS involve drives with SATA interfaces. Enterprise models with SAS interfaces are beginning to become available.
As of 2017, Solid state storage using NAND-flash with PCI-E interfaces are widely available on the market. They are predominantly enterprise drives that utilize a NVMe interface that has lower overhead than the ATA used in SATA or SCSI used in SAS. There is also an interface known as M.2 that is primarily used by consumer SSDs, although not necessarily limited to them. It can provide electrical connectivity for multiple buses, although M.2 SSDs appear to exclusively utilize PCI-E over M.2.
== Power Failure Protection ==
=== Background === On-flash data structures are highly complex and consequently, vulnerable to corruption. Such corruption can result in the loss of *all* drive data and an event such as a PSU failure can result in multiple drives simultaneously failing. Since the drive firmware is not available for review, the only reasonable conclusion is that all drives that lack hardware features to avoid power failure events cannot be trusted. Therefore, such drives are only suitable for use as L2ARC. Flash drives used for top-level vdevs or SLOG devices should have power failure protectionto protect both their own metadata and flushed data. Protection of unflushed data does not occur on mechanical drives and therefore is not a requirement of filesystems in general, which include ZFS. === SAS/SATA drives with power failure protection === A non-exhaustive list of SAS/SATA drives with power failure protection is as follows:
* Crucial MX200
* Samsung PM853T
ZFS only expects storage to protect flushed data. Consequently, solid state === NVMe drives whose with power loss failure protection only protects flushed data is sufficient for ZFS to ensure that data remains safe. This is why the Crucial drives are on this list, despite Anandtech's description of them not having true power loss protection because their design allows in-flight data (i.e. unflushed data) to be lost.[http://www.anandtech.com/show/8528/micron-m600-128gb-256gb-1tb-ssd-review-nda-placeholder]===
=== Background ===Due to the higher performance characteristics of NVMe storage, a separate non-exhaustive list of NVMe drives is also avaliable:
On-flash data structures * Intel 750* Intel DC P3608* Intel DC P3700 === Criteria/process for inclusion into these lists === These lists have been compiled on a volunteer basis by OpenZFS contributors (mainly Richard Yao) from trustworthy sources of information. The lists are highly complex intended to be vendor neutral and consequently, vulnerable are not intended to corruptionbenefit any particular manufacturer. Such corruption can result in the loss Any perceived bias toward any manufacturer is caused by a lack of *all* drive data awareness and an event such as a PSU failure can result in multiple drives simultaneously failinglack of time to research additional options. Since Confirmation of the presence of adequate power loss protection by a reliable source is the only requirement for inclusion into this list. Adequate power loss protection means that the drive firmware must protect both its own internal metadata and all flushed data. Protection of unflushed data is irrelevant and therefore not available for reviewa requirement. ZFS only expects storage to protect flushed data. Consequently, the solid state drives whose power loss protection only reasonable conclusion protects flushed data is sufficient for ZFS to ensure that all drives that lack hardware features data remains safe. Anyone who believes an unlisted drive to avoid provide adequate power failure events cannot be trustedprotection may contact the [[mailing list|OpenZFS mailing list]] with a request for inclusion and substantiation for the claim that power failure protection is provided. ThereforeExamples of substantiation include pictures of drive internals showing the presence of capacitors, statements by well regarded independent review sites such drives are only suitable for use as L2ARCAnandtech and manufacturer specification sheets. The latter are accepted on the honor system until a manufacturer is found to misstate reality on the protection of the drives' own internal metadata structures and/or the protection of flushed data. Thus far, all manufacturers have been honest.
== Flash pages ==
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