Hardware: reworked for sphinx
This commit is contained in:
George Melikov
@@ -1,3 +1,6 @@
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Hardware
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********
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Introduction
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============
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@@ -196,8 +199,7 @@ not be as reliable as it would be on its own.
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misreports its sector size. Such drives are typically NAND-flash
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based solid state drives and older SATA drives from the advanced
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format (4K sector size) transition before Windows XP EoL occurred.
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This can be `manually
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corrected <Performance_tuning#Alignment_Shift_.28ashift.29>`__ at
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This can be :ref:`manually corrected <alignment_shift_ashift>` at
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vdev creation.
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- It is possible for the RAID header to cause misalignment of sector
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writes on RAID 1 by starting the array within a sector on an
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@@ -387,8 +389,8 @@ requires command queuing. Almost all drives manufactured within the past
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system BIOS.
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Each Open ZFS system has different methods for checking whether command
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queuing is supported. On Linux, \`hdparm -I /path/to/device \| grep
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Queue\` is used. On FreeBSD, \`camcontrol identify $DEVICE\` is used.
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queuing is supported. On Linux, ``hdparm -I /path/to/device \| grep
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Queue`` is used. On FreeBSD, ``camcontrol identify $DEVICE`` is used.
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.. _nand_flash_ssds:
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@@ -425,13 +427,13 @@ NVMe drives should be
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to use 4096-byte sectors without metadata prior to being given to ZFS
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for best performance unless they indicate that 512-byte sectors are as
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performant as 4096-byte sectors, although this is unlikely. Lower
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numbers in the Rel_Perf of Supported LBA Sizes from \`smartctl -a
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/dev/$device_namespace\` (for example \`smartctl -a /dev/nvme1n1`)
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numbers in the Rel_Perf of Supported LBA Sizes from ``smartctl -a
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/dev/$device_namespace`` (for example ``smartctl -a /dev/nvme1n1``)
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indicate higher performance low level formats, with 0 being the best.
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The current formatting will be marked by a plus sign under the format
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Fmt.
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You may format a drive using \`nvme format /dev/nvme1n1 -l $ID`. The $ID
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You may format a drive using ``nvme format /dev/nvme1n1 -l $ID``. The $ID
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corresponds to the Id field value from the Supported LBA Sizes SMART
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information.
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@@ -453,12 +455,12 @@ the drive firmware is not available for review, the traditional
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conclusion was that all drives that lack hardware features to avoid
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power failure events cannot be trusted, which was found to be the case
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multiple times in the
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past\ `1 <http://lkcl.net/reports/ssd_analysis.html>`__\ `2 <https://www.usenix.org/system/files/conference/fast13/fast13-final80.pdf>`__\ `3 <http://blog.nordeus.com/dev-ops/power-failure-testing-with-ssds.htm>`__.
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past [#ssd_analysis]_ [#ssd_analysis2]_ [#ssd_analysis3]_.
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Discussion of power failures bricking NAND flash SSDs appears to have
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vanished from literature following the year 2015. SSD manufacturers now
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claim that firmware power loss protection is robust enough to provide
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equivalent protection to hardware power loss protection. Kingston is one
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example\ `4 <https://www.kingston.com/us/solutions/servers-data-centers/ssd-power-loss-protection>`__.
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equivalent protection to hardware power loss protection. `Kingston is one
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example <https://www.kingston.com/us/solutions/servers-data-centers/ssd-power-loss-protection>`__.
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Firmware power loss protection is used to guarantee the protection of
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flushed data and the drives’ own metadata, which is all that filesystems
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such as ZFS need.
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@@ -577,8 +579,8 @@ follows:
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- Intel 320
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- Early reports claimed that the 330 and 335 had power failure
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protection too, but they do
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not.\ `5 <http://blog.nordeus.com/dev-ops/power-failure-testing-with-ssds.htm>`__
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protection too, `but they do
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not <http://blog.nordeus.com/dev-ops/power-failure-testing-with-ssds.htm>`__.
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- Intel 710
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- Intel 730
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@@ -594,8 +596,8 @@ follows:
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- Samsung 845DC Evo
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- Samsung 845DC Pro
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- High sustained write
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IOPS\ `6 <http://www.anandtech.com/show/8319/samsung-ssd-845dc-evopro-preview-exploring-worstcase-iops/5>`__
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- `High sustained write
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IOPS <http://www.anandtech.com/show/8319/samsung-ssd-845dc-evopro-preview-exploring-worstcase-iops/5>`__
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- Toshiba HK4E/HK3E2
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- Toshiba HK4R/HK3R2/HK3R
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@@ -621,7 +623,7 @@ protects flushed data is sufficient for ZFS to ensure that data remains
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safe.
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Anyone who believes an unlisted drive to provide adequate power failure
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protection may contact the `OpenZFS mailing list <mailing_list>`__ with
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protection may contact the :ref:`mailing_lists` with
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a request for inclusion and substantiation for the claim that power
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failure protection is provided. Examples of substantiation include
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pictures of drive internals showing the presence of capacitors,
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@@ -640,7 +642,7 @@ Flash pages
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The smallest unit on a NAND chip that can be written is a flash page.
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The first NAND-flash SSDs on the market had 4096-byte pages. Further
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complicating matters is that the the page size has been doubled twice
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since then. NAND flash SSDs \*should\* report these pages as being
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since then. NAND flash SSDs **should** report these pages as being
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sectors, but so far, all of them incorrectly report 512-byte sectors for
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Windows XP compatibility. The consequence is that we have a similar
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situation to what we had with early advanced format hard drives.
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@@ -695,8 +697,8 @@ need to run TRIM on them. However, they cost more per GB than NAND flash
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(as of 2020). The enterprise models make excellent SLOG devices. Here is
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a list of models that are known to perform well:
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- Intel DC
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P4800X\ `7 <https://www.servethehome.com/intel-optane-hands-on-real-world-benchmark-and-test-results/>`__
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- `Intel DC
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P4800X <https://www.servethehome.com/intel-optane-hands-on-real-world-benchmark-and-test-results/>`__
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- This gives basically the highest performance you can get as of
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June 2020.
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@@ -793,5 +795,13 @@ UPS batteries
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The lead acid batteries in UPS units generally need to be replaced
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regularly to ensure that they provide power during power outages. For
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home systems, this is every 3 to 5 years, although this varies with
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temperature\ `8 <https://www.apc.com/us/en/faqs/FA158934/>`__. For
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temperature [#ups_temp]_. For
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enterprise systems, contact your vendor.
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.. rubric:: Footnotes
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.. [#ssd_analysis] <http://lkcl.net/reports/ssd_analysis.html>
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.. [#ssd_analysis2] <https://www.usenix.org/system/files/conference/fast13/fast13-final80.pdf>
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.. [#ssd_analysis3] <http://blog.nordeus.com/dev-ops/power-failure-testing-with-ssds.htm>
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.. [#ups_temp] <https://www.apc.com/us/en/faqs/FA158934/>
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