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词条 U.2
释义

  1. History

  2. Connector

  3. Availability

  4. U.2 compared with M.2

  5. References

{{POV|date=September 2018}}

U.2, formerly known as SFF-8639, is a computer interface for connecting SSDs to a computer. It uses up to four PCI Express lanes.

It is developed for the enterprise market and designed to support new PCI Express drives along with SAS and SATA drives.

History

The Enterprise SSD form factor was developed by the SSD Form Factor Working Group (SFFWG). The specification was released on December 20, 2011, as a mechanism for providing PCI Express connections to SSDs for the enterprise market. Goals included supporting existing 2.5" and 3.5" mechanical enclosures, to be hot swappable and to allow legacy SAS and SATA drives to be mixed using the same connector family.[1]

In June 2015 the SFFWG announced that the connector was being renamed to U.2.[2]

Connector

The U.2 connector is mechanically identical to the SATA Express device plug, but provides four PCI Express lanes through a different usage of available pins.[3][4]

U.2 devices may be connected to an M.2 port using an adapter.[5]

Availability

In November 2015, Intel introduced their 750 series{{what?|date=September 2017}} which came in both PCI Express and U.2 variants.[6]

U.2 compared with M.2

  • U.2 supports hot-swap[7] and M.2 does not.[8]
  • U.2 drives are easier to keep cool than an M.2 drive. Most U.2 drives use their incorporated enclosure as a large heatsink[9] but most M.2 drives come with no heatsink.[10]
  • U.2 drives are able to sustain higher speeds for a longer duration than M.2 drives due to earlier thermal throttling of M.2 drives.[11]
    • Since M.2 drives typically have no heatsink and are not able to be positioned in a location with ideal airflow, they are more likely to suffer from thermal throttling than a U.2 drive.[11]
    • While a drive is suffering from thermal throttling, which is necessary to protect the drive from damage, it slows down the drive's performance. This means the drive is no longer providing its advertised speed. Some M.2 drives may only be able to provide their advertised speeds for brief durations before thermal throttling slows them down.[11]
  • U.2 drives can have higher storage capacities than M.2 drives.
    • Since U.2 drives are physically larger than M.2 drives, it is easier for the manufacturer to place more flash storage chips on them.[12]

References

1. ^{{Cite web|url = http://www.ssdformfactor.org/docs/SSD_Form_Factor_Version1_00.pdf|title = Enterprise SSD Form Factor version 1.0|last =|first =|date = 20 December 2011|website = SSD Form Factor Working Group|archive-url =|archive-date =|dead-url =|accessdate =}}
2. ^{{Cite news|url = http://www.tomshardware.com/news/sff-8639-u.2-pcie-ssd-nvme,29321.html|title = SFFWG Renames PCIe SSD SFF-8639 Connector To U.2|date = 2015-06-05|work = Tom's Hardware|accessdate = 2017-07-16}}
3. ^{{cite web|url = http://www.ssdformfactor.org/docs/SSD_Form_Factor_Version1_a.pdf#page=48|title = Figure 37: Pin usage across Existing standards|last =|first =|date =|website =|archive-url =|archive-date =|dead-url =|accessdate =}}
4. ^{{cite web|title=U.2 connector pinout|url=http://pinoutguide.com/HD/U.2_SATA_connector_pinout.shtml|website=pinoutguide.com}}
5. ^{{Cite news|url = http://techreport.com/news/30251/intel-bridges-the-u-2-gap-with-an-m-2-cable-for-its-750-series-ssd|title = Intel bridges the U.2 gap with an M.2 cable for its 750 Series SSD|work = The Tech Report|accessdate = 2017-07-16}}
6. ^{{Cite news|url = http://www.trustedreviews.com/intel-ssd-750-review|title = Intel SSD 750 review {{!}} TrustedReviews|work = TrustedReviews|accessdate = 2017-07-16}}
7. ^{{Cite web|url=http://www.ssdformfactor.org/docs/SSD_Form_Factor_Version1_00.pdf|title=SSD Form Factor|last=|first=|date=|website=|archive-url=|archive-date=|dead-url=|access-date=}}
8. ^{{Cite web|url=https://www.kingston.com/us/ssd/system-builder/m2_faq|title=M 2 SSD - Frequently Asked Questions {{!}} Kingston|website=Kingston Technology Company|language=en-US|access-date=2018-04-17}}
9. ^{{Cite news|url=https://www.tweaktown.com/articles/7645/intel-750-nvme-400gb-ssd-bootable-raid-report/index2.html|title=Intel 750 NVMe 400GB U.2 SSD Bootable RAID 0 Report|date=2016-04-12|work=TweakTown|access-date=2018-04-17|language=en-us}}
10. ^{{Cite news|url=https://www.anandtech.com/show/9856/angelbird-wings-px1-m2-adapter-review-do-ssds-need-heatsinks/8|title=The Angelbird Wings PX1 M.2 Adapter Review: Do M.2 SSDs Need Heatsinks?|last=Tallis|first=Billy|access-date=2018-04-17}}
11. ^1 2 {{Cite news|url=https://www.pugetsystems.com/labs/articles/Samsung-950-Pro-M-2-Throttling-Analysis-776/#Conclusion|title=Samsung 950 Pro M.2 Throttling Analysis|last=Bach|first=Matt|work=Puget Systems|access-date=2018-04-17|language=en}}
12. ^{{Cite web|url=https://rog.asus.com/articles/hands-on/easy-guide-to-ssds-sata-msata-m-2-and-u-2/|title=Easy Guide to SSDs: SATA, mSATA, M.2 and U.2|website=ROG - Republic of Gamers Global|language=en|access-date=2018-04-17}}
{{Solid-state drive}}

2 : Computer buses|Computer connectors
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