zonefs is a very simple file system exposing each zone of a zoned block
device as a file. Unlike a regular file system with zoned block device
support (e.g. f2fs or the on-going btrfs effort), zonefs does not hide
the sequential write constraint of zoned block devices to the user.
Files representing sequential write zones of the device must be written
sequentially starting from the end of the file (append only writes).
zonefs is not a POSIX compliant file system. It's goal is to simplify
the implementation of zoned block devices support in applications by
replacing raw block device file accesses with a richer file based API,
avoiding relying on direct block device file ioctls which may
be more obscure to developers. One example of this approach is the
implementation of LSM (log-structured merge) tree structures (such as
used in RocksDB and LevelDB) on zoned block devices by allowing SSTables
to be stored in a zone file similarly to a regular file system rather
than as a range of sectors of a zoned device. The introduction of the
higher level construct "one file is one zone" can help reducing the
amount of changes needed in the application while at the same time
allowing the use of zoned block devices with various programming
languages other than C.
zonefs IO management implementation uses the new iomap generic code.
Changes from v5:
* Added simple description of zoned block devices to the documentation,
as suggested by Johannes.
* Added a 64-char max label field to the super block to allow label
based identification of volumes using libblkid (checked with a patch
to libblkid).
Changes from v4:
* Use octal values for file and directory permissions
* Set initial directory permissions to 0555 (no write permission)
* Prevent setting write permissions for directories
Changes from v3:
* Fixed many typos in the documentation
* Use symbolic file permission macros instead of octal values
(checkpatch.pl complains about this)
Changes from v2:
* Address comments and suggestions from Darrick:
- Make the inode of OFFLINE and READONLY zones immutable when
mounting. Also do this during zone information check after an IO
error.
- Change super block CRC seed to ~0.
- Avoid potential compiler warning in zonefs_create_zgroup().
* Fixed endianness related compilation warning detected by kbuild bot.
Changes from v1:
* Fixed comment typo
* Improved documentation as suggested by Hannes
Damien Le Moal (2):
fs: New zonefs file system
zonefs: Add documentation
Documentation/filesystems/zonefs.txt | 241 ++++++
MAINTAINERS | 10 +
fs/Kconfig | 1 +
fs/Makefile | 1 +
fs/zonefs/Kconfig | 9 +
fs/zonefs/Makefile | 4 +
fs/zonefs/super.c | 1177 ++++++++++++++++++++++++++
fs/zonefs/zonefs.h | 175 ++++
include/uapi/linux/magic.h | 1 +
9 files changed, 1619 insertions(+)
create mode 100644 Documentation/filesystems/zonefs.txt
create mode 100644 fs/zonefs/Kconfig
create mode 100644 fs/zonefs/Makefile
create mode 100644 fs/zonefs/super.c
create mode 100644 fs/zonefs/zonefs.h
--
2.24.1
Add the new file Documentation/filesystems/zonefs.txt to document
zonefs principles and user-space tool usage.
Signed-off-by: Damien Le Moal <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
---
Documentation/filesystems/zonefs.txt | 241 +++++++++++++++++++++++++++
MAINTAINERS | 1 +
2 files changed, 242 insertions(+)
create mode 100644 Documentation/filesystems/zonefs.txt
diff --git a/Documentation/filesystems/zonefs.txt b/Documentation/filesystems/zonefs.txt
new file mode 100644
index 000000000000..97008eb8ff82
--- /dev/null
+++ b/Documentation/filesystems/zonefs.txt
@@ -0,0 +1,241 @@
+ZoneFS - Zone filesystem for Zoned block devices
+
+Overview
+========
+
+zonefs is a very simple file system exposing each zone of a zoned block device
+as a file. Unlike a regular POSIX-compliant file system with native zoned block
+device support (e.g. f2fs), zonefs does not hide the sequential write
+constraint of zoned block devices to the user. Files representing sequential
+write zones of the device must be written sequentially starting from the end
+of the file (append only writes).
+
+As such, zonefs is in essence closer to a raw block device access interface
+than to a full featured POSIX file system. The goal of zonefs is to simplify
+the implementation of zoned block device support in applications by replacing
+raw block device file accesses with a richer file API, avoiding relying on
+direct block device file ioctls which may be more obscure to developers. One
+example of this approach is the implementation of LSM (log-structured merge)
+tree structures (such as used in RocksDB and LevelDB) on zoned block devices
+by allowing SSTables to be stored in a zone file similarly to a regular file
+system rather than as a range of sectors of the entire disk. The introduction
+of the higher level construct "one file is one zone" can help reducing the
+amount of changes needed in the application as well as introducing support for
+different application programming languages.
+
+Zoned block devices
+-------------------
+
+Zoned storage devices belong to a class of storage devices with an address
+space that is divided into zones. A zone is a group of consecutive LBAs and all
+zones are contiguous (there are no LBA gaps). Zones may have different types.
+* Conventional zones: there are no access constraints to LBAs belonging to
+ conventional zones. Any read or write access can be executed, similarly to a
+ regular block device.
+* Sequential zones: these zones accept random reads but must be written
+ sequentially. Each sequential zone has a write pointer maintained by the
+ device that keeps track of the mandatory start LBA position of the next write
+ to the device. As a result of this write constraint, LBAs in a sequential zone
+ cannot be overwritten. Sequential zones must first be erased using a special
+ command (zone reset) before rewritting.
+
+Zoned storage devices can be implemented using various recording and media
+technologies. The most common form of zoned storage today uses the SCSI Zoned
+Block Commands (ZBC) and Zoned ATA Commands (ZAC) interfaces on Shingled
+Magnetic Recording (SMR) HDDs.
+
+Solid State Disks (SSD) storage devices can also implement a zoned interface
+to, for instance, reduce internal write amplification due to garbage collection.
+The NVMe Zoned NameSpace (ZNS) is a technical proposal of the NVMe standard
+committee aiming at adding a zoned storage interface to the NVMe protocol.
+
+zonefs on-disk metadata
+-----------------------
+
+zonefs on-disk metadata is reduced to an immutable super block which
+persistently stores a magic number and optional feature flags and values. On
+mount, zonefs uses blkdev_report_zones() to obtain the device zone configuration
+and populates the mount point with a static file tree solely based on this
+information. File sizes come from the device zone type and write pointer
+position managed by the device itself.
+
+The super block is always written on disk at sector 0. The first zone of the
+device storing the super block is never exposed as a zone file by zonefs. If
+the zone containing the super block is a sequential zone, the mkzonefs format
+tool always "finishes" the zone, that is, it transitions the zone to a full
+state to make it read-only, preventing any data write.
+
+Zone type sub-directories
+-------------------------
+
+Files representing zones of the same type are grouped together under the same
+sub-directory automatically created on mount.
+
+For conventional zones, the sub-directory "cnv" is used. This directory is
+however created if and only if the device has usable conventional zones. If
+the device only has a single conventional zone at sector 0, the zone will not
+be exposed as a file as it will be used to store the zonefs super block. For
+such devices, the "cnv" sub-directory will not be created.
+
+For sequential write zones, the sub-directory "seq" is used.
+
+These two directories are the only directories that exist in zonefs. Users
+cannot create other directories and cannot rename nor delete the "cnv" and
+"seq" sub-directories.
+
+The size of the directories indicated by the st_size field of struct stat,
+obtained with the stat() or fstat() system calls, indicates the number of files
+existing under the directory.
+
+Zone files
+----------
+
+Zone files are named using the number of the zone they represent within the set
+of zones of a particular type. That is, both the "cnv" and "seq" directories
+contain files named "0", "1", "2", ... The file numbers also represent
+increasing zone start sector on the device.
+
+All read and write operations to zone files are not allowed beyond the file
+maximum size, that is, beyond the zone size. Any access exceeding the zone
+size is failed with the -EFBIG error.
+
+Creating, deleting, renaming or modifying any attribute of files and
+sub-directories is not allowed.
+
+The number of blocks of a file as reported by stat() and fstat() indicates the
+size of the file zone, or in other words, the maximum file size.
+
+Conventional zone files
+-----------------------
+
+The size of conventional zone files is fixed to the size of the zone they
+represent. Conventional zone files cannot be truncated.
+
+These files can be randomly read and written, using any form of IO operation:
+buffered IOs, direct IOs, memory mapped IOs (mmap), etc. There are no IO
+constraint for these files beyond the file size limit mentioned above.
+
+Sequential zone files
+---------------------
+
+The size of sequential zone files present in the "seq" sub-directory represents
+the file's zone write pointer position relative to the zone start sector.
+
+Sequential zone files can only be written sequentially, starting from the file
+end, that is, write operations can only be append writes. Zonefs makes no
+attempt at accepting random writes and will fail any write request that has a
+start offset not corresponding to the end of the last issued write.
+
+In order to give guarantees regarding write ordering, zonefs also prevents
+buffered writes and mmap writes for sequential files. Only direct IO writes are
+accepted. There are no restrictions on read operations nor on the type of IO
+used to request reads (buffered IOs, direct IOs and mmap reads are all
+accepted).
+
+Truncating sequential zone files is allowed only down to 0, in which case, the
+zone is reset to rewind the file zone write pointer position to the start of
+the zone, or up to the zone size, in which case the file's zone is transitioned
+to the FULL state (finish zone operation).
+
+zonefs format options
+---------------------
+
+Several optional features of zonefs can be enabled at format time.
+* Conventional zone aggregation: ranges of contiguous conventional zones can be
+ aggregated into a single larger file instead of the default one file per zone.
+* File ownership: The owner UID and GID of zone files is by default 0 (root)
+ but can be changed to any valid UID/GID.
+* File access permissions: the default 640 access permissions can be changed.
+
+User Space Tools
+================
+
+The mkzonefs tool is used to format zoned block devices for use with zonefs.
+This tool is available on Github at:
+
+https://github.com/damien-lemoal/zonefs-tools
+
+zonefs-tools also includes a test suite which can be run against any zoned
+block device, including null_blk block device created with zoned mode.
+
+Examples
+--------
+
+The following formats a 15TB host-managed SMR HDD with 256 MB zones
+with the conventional zones aggregation feature enabled.
+
+# mkzonefs -o aggr_cnv /dev/sdX
+# mount -t zonefs /dev/sdX /mnt
+# ls -l /mnt/
+total 0
+dr-xr-xr-x 2 root root 1 Nov 25 13:23 cnv
+dr-xr-xr-x 2 root root 55356 Nov 25 13:23 seq
+
+The size of the zone files sub-directories indicate the number of files
+existing for each type of zones. In this example, there is only one
+conventional zone file (all conventional zones are aggregated under a single
+file).
+
+# ls -l /mnt/cnv
+total 137101312
+-rw-r----- 1 root root 140391743488 Nov 25 13:23 0
+
+This aggregated conventional zone file can be used as a regular file.
+
+# mkfs.ext4 /mnt/cnv/0
+# mount -o loop /mnt/cnv/0 /data
+
+The "seq" sub-directory grouping files for sequential write zones has in this
+example 55356 zones.
+
+# ls -lv /mnt/seq
+total 14511243264
+-rw-r----- 1 root root 0 Nov 25 13:23 0
+-rw-r----- 1 root root 0 Nov 25 13:23 1
+-rw-r----- 1 root root 0 Nov 25 13:23 2
+...
+-rw-r----- 1 root root 0 Nov 25 13:23 55354
+-rw-r----- 1 root root 0 Nov 25 13:23 55355
+
+For sequential write zone files, the file size changes as data is appended at
+the end of the file, similarly to any regular file system.
+
+# dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
+1+0 records in
+1+0 records out
+4096 bytes (4.1 kB, 4.0 KiB) copied, 1.05112 s, 3.9 kB/s
+
+# ls -l /mnt/seq/0
+-rw-r----- 1 root root 4096 Nov 25 13:23 /mnt/seq/0
+
+The written file can be truncated to the zone size, preventing any further
+write operation.
+
+# truncate -s 268435456 /mnt/seq/0
+# ls -l /mnt/seq/0
+-rw-r----- 1 root root 268435456 Nov 25 13:49 /mnt/seq/0
+
+Truncation to 0 size allows freeing the file zone storage space and restart
+append-writes to the file.
+
+# truncate -s 0 /mnt/seq/0
+# ls -l /mnt/seq/0
+-rw-r----- 1 root root 0 Nov 25 13:49 /mnt/seq/0
+
+Since files are statically mapped to zones on the disk, the number of blocks of
+a file as reported by stat() and fstat() indicates the size of the file zone.
+
+# stat /mnt/seq/0
+ File: /mnt/seq/0
+ Size: 0 Blocks: 524288 IO Block: 4096 regular empty file
+Device: 870h/2160d Inode: 50431 Links: 1
+Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 0/ root)
+Access: 2019-11-25 13:23:57.048971997 +0900
+Modify: 2019-11-25 13:52:25.553805765 +0900
+Change: 2019-11-25 13:52:25.553805765 +0900
+ Birth: -
+
+The number of blocks of the file ("Blocks") in units of 512B blocks gives the
+maximum file size of 524288 * 512 B = 256 MB, corresponding to the device zone
+size in this example. Of note is that the "IO block" field always indicates the
+minimum IO size for writes and corresponds to the device physical sector size.
diff --git a/MAINTAINERS b/MAINTAINERS
index 2ffdeaa7191e..d658037e9843 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18312,6 +18312,7 @@ L: [email protected]
T: git git://git.kernel.org/pub/scm/linux/kernel/git/dlemoal/zonefs.git
S: Maintained
F: fs/zonefs/
+F: Documentation/filesystems/zonefs.txt
ZPOOL COMPRESSED PAGE STORAGE API
M: Dan Streetman <[email protected]>
--
2.24.1
Looks good,
Reviewed-by: Johannes Thumshirn <[email protected]>
Hi Damien,
Here are a few editorial comments for you...
On 1/8/20 12:36 AM, Damien Le Moal wrote:
> Add the new file Documentation/filesystems/zonefs.txt to document
> zonefs principles and user-space tool usage.
>
> Signed-off-by: Damien Le Moal <[email protected]>
> Reviewed-by: Darrick J. Wong <[email protected]>
> ---
> Documentation/filesystems/zonefs.txt | 241 +++++++++++++++++++++++++++
> MAINTAINERS | 1 +
> 2 files changed, 242 insertions(+)
> create mode 100644 Documentation/filesystems/zonefs.txt
>
> diff --git a/Documentation/filesystems/zonefs.txt b/Documentation/filesystems/zonefs.txt
> new file mode 100644
> index 000000000000..97008eb8ff82
> --- /dev/null
> +++ b/Documentation/filesystems/zonefs.txt
> @@ -0,0 +1,241 @@
> +ZoneFS - Zone filesystem for Zoned block devices
> +
> +Overview
> +========
> +
> +zonefs is a very simple file system exposing each zone of a zoned block device
> +as a file. Unlike a regular POSIX-compliant file system with native zoned block
> +device support (e.g. f2fs), zonefs does not hide the sequential write
> +constraint of zoned block devices to the user. Files representing sequential
> +write zones of the device must be written sequentially starting from the end
> +of the file (append only writes).
> +
> +As such, zonefs is in essence closer to a raw block device access interface
> +than to a full featured POSIX file system. The goal of zonefs is to simplify
full-featured
> +the implementation of zoned block device support in applications by replacing> +direct block device file ioctls which may be more obscure to developers. One
> +example of this approach is the implementation of LSM (log-structured merge)
> +tree structures (such as used in RocksDB and LevelDB) on zoned block devices
> +by allowing SSTables to be stored in a zone file similarly to a regular file
> +system rather than as a range of sectors of the entire disk. The introduction
> +of the higher level construct "one file is one zone" can help reducing the
> +amount of changes needed in the application as well as introducing support for
> +different application programming languages.
> +
> +Zoned block devices
> +-------------------
> +
> +Zoned storage devices belong to a class of storage devices with an address
> +space that is divided into zones. A zone is a group of consecutive LBAs and all
> +zones are contiguous (there are no LBA gaps). Zones may have different types.
> +* Conventional zones: there are no access constraints to LBAs belonging to
> + conventional zones. Any read or write access can be executed, similarly to a
> + regular block device.
> +* Sequential zones: these zones accept random reads but must be written
> + sequentially. Each sequential zone has a write pointer maintained by the
> + device that keeps track of the mandatory start LBA position of the next write
> + to the device. As a result of this write constraint, LBAs in a sequential zone
> + cannot be overwritten. Sequential zones must first be erased using a special
> + command (zone reset) before rewritting.
rewriting.
> +
> +Zoned storage devices can be implemented using various recording and media
> +technologies. The most common form of zoned storage today uses the SCSI Zoned
> +Block Commands (ZBC) and Zoned ATA Commands (ZAC) interfaces on Shingled
> +Magnetic Recording (SMR) HDDs.
> +
> +Solid State Disks (SSD) storage devices can also implement a zoned interface
> +to, for instance, reduce internal write amplification due to garbage collection.
> +The NVMe Zoned NameSpace (ZNS) is a technical proposal of the NVMe standard
> +committee aiming at adding a zoned storage interface to the NVMe protocol.
> +
> +zonefs on-disk metadata
> +-----------------------
> +
> +zonefs on-disk metadata is reduced to an immutable super block which
> +persistently stores a magic number and optional feature flags and values. On
> +mount, zonefs uses blkdev_report_zones() to obtain the device zone configuration
> +and populates the mount point with a static file tree solely based on this
> +information. File sizes come from the device zone type and write pointer
> +position managed by the device itself.
> +
> +The super block is always written on disk at sector 0. The first zone of the
> +device storing the super block is never exposed as a zone file by zonefs. If
> +the zone containing the super block is a sequential zone, the mkzonefs format
> +tool always "finishes" the zone, that is, it transitions the zone to a full
> +state to make it read-only, preventing any data write.
> +
> +Zone type sub-directories
> +-------------------------
> +
> +Files representing zones of the same type are grouped together under the same
> +sub-directory automatically created on mount.
> +
> +For conventional zones, the sub-directory "cnv" is used. This directory is
> +however created if and only if the device has usable conventional zones. If
> +the device only has a single conventional zone at sector 0, the zone will not
> +be exposed as a file as it will be used to store the zonefs super block. For
> +such devices, the "cnv" sub-directory will not be created.
> +
> +For sequential write zones, the sub-directory "seq" is used.
> +
> +These two directories are the only directories that exist in zonefs. Users
> +cannot create other directories and cannot rename nor delete the "cnv" and
> +"seq" sub-directories.
> +
> +The size of the directories indicated by the st_size field of struct stat,
> +obtained with the stat() or fstat() system calls, indicates the number of files
> +existing under the directory.
> +
> +Zone files
> +----------
> +
> +Zone files are named using the number of the zone they represent within the set
> +of zones of a particular type. That is, both the "cnv" and "seq" directories
> +contain files named "0", "1", "2", ... The file numbers also represent
> +increasing zone start sector on the device.
> +
> +All read and write operations to zone files are not allowed beyond the file
> +maximum size, that is, beyond the zone size. Any access exceeding the zone
> +size is failed with the -EFBIG error.
> +
> +Creating, deleting, renaming or modifying any attribute of files and
> +sub-directories is not allowed.
> +
> +The number of blocks of a file as reported by stat() and fstat() indicates the
> +size of the file zone, or in other words, the maximum file size.
> +
> +Conventional zone files
> +-----------------------
> +
> +The size of conventional zone files is fixed to the size of the zone they
> +represent. Conventional zone files cannot be truncated.
> +
> +These files can be randomly read and written, using any form of IO operation:
> +buffered IOs, direct IOs, memory mapped IOs (mmap), etc. There are no IO
> +constraint for these files beyond the file size limit mentioned above.
I would prefer to see "I/O" here instead of "IO", but that's just a nit.
> +
> +Sequential zone files
> +---------------------
> +
> +The size of sequential zone files present in the "seq" sub-directory represents
> +the file's zone write pointer position relative to the zone start sector.
> +
> +Sequential zone files can only be written sequentially, starting from the file
> +end, that is, write operations can only be append writes. Zonefs makes no
> +attempt at accepting random writes and will fail any write request that has a
> +start offset not corresponding to the end of the last issued write.
> +
> +In order to give guarantees regarding write ordering, zonefs also prevents
> +buffered writes and mmap writes for sequential files. Only direct IO writes are
> +accepted. There are no restrictions on read operations nor on the type of IO
> +used to request reads (buffered IOs, direct IOs and mmap reads are all
> +accepted).
ditto.
> +
> +Truncating sequential zone files is allowed only down to 0, in which case, the
> +zone is reset to rewind the file zone write pointer position to the start of
> +the zone, or up to the zone size, in which case the file's zone is transitioned
> +to the FULL state (finish zone operation).
> +
> +zonefs format options
> +---------------------
> +
> +Several optional features of zonefs can be enabled at format time.
> +* Conventional zone aggregation: ranges of contiguous conventional zones can be
> + aggregated into a single larger file instead of the default one file per zone.
> +* File ownership: The owner UID and GID of zone files is by default 0 (root)
> + but can be changed to any valid UID/GID.
> +* File access permissions: the default 640 access permissions can be changed.
> +
> +User Space Tools
> +================
> +
> +The mkzonefs tool is used to format zoned block devices for use with zonefs.
> +This tool is available on Github at:
> +
> +https://github.com/damien-lemoal/zonefs-tools
> +
> +zonefs-tools also includes a test suite which can be run against any zoned
> +block device, including null_blk block device created with zoned mode.
> +
> +Examples
> +--------
> +
> +The following formats a 15TB host-managed SMR HDD with 256 MB zones
> +with the conventional zones aggregation feature enabled.
> +
> +# mkzonefs -o aggr_cnv /dev/sdX
> +# mount -t zonefs /dev/sdX /mnt
> +# ls -l /mnt/
> +total 0
> +dr-xr-xr-x 2 root root 1 Nov 25 13:23 cnv
> +dr-xr-xr-x 2 root root 55356 Nov 25 13:23 seq
> +
> +The size of the zone files sub-directories indicate the number of files
> +existing for each type of zones. In this example, there is only one
> +conventional zone file (all conventional zones are aggregated under a single
> +file).
> +
> +# ls -l /mnt/cnv
> +total 137101312
> +-rw-r----- 1 root root 140391743488 Nov 25 13:23 0
> +
> +This aggregated conventional zone file can be used as a regular file.
> +
> +# mkfs.ext4 /mnt/cnv/0
> +# mount -o loop /mnt/cnv/0 /data
> +
> +The "seq" sub-directory grouping files for sequential write zones has in this
> +example 55356 zones.
> +
> +# ls -lv /mnt/seq
> +total 14511243264
> +-rw-r----- 1 root root 0 Nov 25 13:23 0
> +-rw-r----- 1 root root 0 Nov 25 13:23 1
> +-rw-r----- 1 root root 0 Nov 25 13:23 2
> +...
> +-rw-r----- 1 root root 0 Nov 25 13:23 55354
> +-rw-r----- 1 root root 0 Nov 25 13:23 55355
> +
> +For sequential write zone files, the file size changes as data is appended at
> +the end of the file, similarly to any regular file system.
> +
> +# dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
> +1+0 records in
> +1+0 records out
> +4096 bytes (4.1 kB, 4.0 KiB) copied, 1.05112 s, 3.9 kB/s
Still slow. You don't want to change that?
> +
> +# ls -l /mnt/seq/0
> +-rw-r----- 1 root root 4096 Nov 25 13:23 /mnt/seq/0
> +
> +The written file can be truncated to the zone size, preventing any further
> +write operation.
> +
> +# truncate -s 268435456 /mnt/seq/0
> +# ls -l /mnt/seq/0
> +-rw-r----- 1 root root 268435456 Nov 25 13:49 /mnt/seq/0
> +
> +Truncation to 0 size allows freeing the file zone storage space and restart
> +append-writes to the file.
> +
> +# truncate -s 0 /mnt/seq/0
> +# ls -l /mnt/seq/0
> +-rw-r----- 1 root root 0 Nov 25 13:49 /mnt/seq/0
> +
> +Since files are statically mapped to zones on the disk, the number of blocks of
> +a file as reported by stat() and fstat() indicates the size of the file zone.
> +
> +# stat /mnt/seq/0
> + File: /mnt/seq/0
> + Size: 0 Blocks: 524288 IO Block: 4096 regular empty file
> +Device: 870h/2160d Inode: 50431 Links: 1
> +Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 0/ root)
> +Access: 2019-11-25 13:23:57.048971997 +0900
> +Modify: 2019-11-25 13:52:25.553805765 +0900
> +Change: 2019-11-25 13:52:25.553805765 +0900
> + Birth: -
> +
> +The number of blocks of the file ("Blocks") in units of 512B blocks gives the
> +maximum file size of 524288 * 512 B = 256 MB, corresponding to the device zone
> +size in this example. Of note is that the "IO block" field always indicates the
> +minimum IO size for writes and corresponds to the device physical sector size.
thanks.
--
~Randy
Randy,
On 2020/01/15 3:25, Randy Dunlap wrote:
> Hi Damien,
>
> Here are a few editorial comments for you...
Thanks ! All fixed.
[...]
>> +For sequential write zone files, the file size changes as data is appended at
>> +the end of the file, similarly to any regular file system.
>> +
>> +# dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
>> +1+0 records in
>> +1+0 records out
>> +4096 bytes (4.1 kB, 4.0 KiB) copied, 1.05112 s, 3.9 kB/s
>
> Still slow. You don't want to change that?
Good catch. I thought I had fixed that. Here is the updated dd run,
after making sure that the disk has woken up from low power state before
running:
dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 conv=notrunc oflag=direct
1+0 records in
1+0 records out
4096 bytes (4.1 kB, 4.0 KiB) copied, 0.00044121 s, 9.3 MB/s
The HDD write cache is on and empty at the time of running this, which
explains the much lower I/O time.
--
Damien Le Moal
Western Digital Research