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([106.84.135.2]) by smtp.gmail.com with ESMTPSA id jo13-20020a170903054d00b001715a939ac5sm1772154plb.295.2022.08.26.09.36.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Aug 2022 09:36:13 -0700 (PDT) From: Sam Li To: qemu-devel@nongnu.org Cc: stefanha@redhat.com, damien.lemoal@opensource.wdc.com, Dmitry.Fomichev@wdc.com, hare@suse.de, qemu-block@nongnu.org, hreitz@redhat.com, eblake@redhat.com, armbru@redhat.com, fam@euphon.net, kwolf@redhat.com, Sam Li Subject: [PATCH v8 7/7] docs/zoned-storage: add zoned device documentation Date: Sat, 27 Aug 2022 00:35:33 +0800 Message-Id: <20220826163533.9393-1-faithilikerun@gmail.com> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::1032; envelope-from=faithilikerun@gmail.com; helo=mail-pj1-x1032.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01, T_SPF_TEMPERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" Add the documentation about the zoned device support to virtio-blk emulation. Signed-off-by: Sam Li Reviewed-by: Stefan Hajnoczi --- docs/devel/zoned-storage.rst | 41 ++++++++++++++++++++++++++ docs/system/qemu-block-drivers.rst.inc | 6 ++++ 2 files changed, 47 insertions(+) create mode 100644 docs/devel/zoned-storage.rst diff --git a/docs/devel/zoned-storage.rst b/docs/devel/zoned-storage.rst new file mode 100644 index 0000000000..ead2d149cc --- /dev/null +++ b/docs/devel/zoned-storage.rst @@ -0,0 +1,41 @@ +============= +zoned-storage +============= + +Zoned Block Devices (ZBDs) devide the LBA space into block regions called zones +that are larger than the LBA size. It can only allow sequential writes, which +reduces write amplification in SSDs, leading to higher throughput and increased +capacity. More details about ZBDs can be found at: + +https://zonedstorage.io/docs/introduction/zoned-storage + +1. Block layer APIs for zoned storage +------------------------------------- +QEMU block layer has three zoned storage model: +- BLK_Z_HM: This model only allows sequential writes access. It supports a set +of ZBD-specific I/O request that used by the host to manage device zones. +- BLK_Z_HA: It deals with both sequential writes and random writes access. +- BLK_Z_NONE: Regular block devices and drive-managed ZBDs are treated as +non-zoned devices. + +The block device information resides inside BlockDriverState. QEMU uses +BlockLimits struct(BlockDriverState::bl) that is continuously accessed by the +block layer while processing I/O requests. A BlockBackend has a root pointer to +a BlockDriverState graph(for example, raw format on top of file-posix). The +zoned storage information can be propagated from the leaf BlockDriverState all +the way up to the BlockBackend. If the zoned storage model in file-posix is +set to BLK_Z_HM, then block drivers will declare support for zoned host device. + +The block layer APIs support commands needed for zoned storage devices, +including report zones, four zone operations, and zone append. + +2. Emulating zoned storage controllers +-------------------------------------- +When the BlockBackend's BlockLimits model reports a zoned storage device, users +like the virtio-blk emulation or the qemu-io-cmds.c utility can use block layer +APIs for zoned storage emulation or testing. + +For example, the command line for zone report testing a null_blk device of +qemu-io-cmds.c is: +$ path/to/qemu-io --image-opts driver=zoned_host_device,filename=/dev/nullb0 -c +"zrp offset nr_zones" diff --git a/docs/system/qemu-block-drivers.rst.inc b/docs/system/qemu-block-drivers.rst.inc index dfe5d2293d..0b97227fd9 100644 --- a/docs/system/qemu-block-drivers.rst.inc +++ b/docs/system/qemu-block-drivers.rst.inc @@ -430,6 +430,12 @@ Hard disks you may corrupt your host data (use the ``-snapshot`` command line option or modify the device permissions accordingly). +Zoned block devices + Zoned block devices can be passed through to the guest if the emulated storage + controller supports zoned storage. Use ``--blockdev zoned_host_device, + node-name=drive0,filename=/dev/nullb0`` to pass through ``/dev/nullb0`` + as ``drive0``. + Windows ^^^^^^^