minimum allocation size for devices. Use this information to
automatically increase ZFS's minimum allocation size for new top-level
vdevs to a value that more closely matches the optimum device
allocation size.
Use GEOM's stripesize attribute, if set, as the physical sector
size of the GEOM.
Calculate the minimum blocksize of each metaslab class. Use the
calculated value instead of SPA_MINBLOCKSIZE (512b) when determining
the likelyhood of compression yeilding a reduction in physical space
usage.
Report devices with sub-optimal block size configuration in "zpool
status". Also properly fail attempts to attach devices with a
logical block size greater than 8kB, since this will cause corruption
to ZFS's label area.
Sponsored by: Spectra Logic Corporaion
MFC after: 2 weeks
Background
==========
Many modern devices use physical allocation units that are much
larger than the minimum logical allocation size accessible by
external commands. Two prevalent examples of this are 512e disk
drives (512b logical sector, 4K physical sector) and flash devices
(512b logical sector, 4K or larger allocation block size, and 128k
or larger erase block size). Operations that modify less than the
physical sector size result in a costly read-modify-write or garbage
collection sequence on these devices.
Simply exporting the true physical sector of the device to ZFS would
yield optimal performance, but has two serious drawbacks:
1) Existing pools created with devices that have different logical
and physical block sizes, but were configured to use the logical
block size (e.g. because the OS version used for pool construction
reported the logical block size instead of the physical block
size) will suddenly find that the vdev allocation size has
increased. This can be easily tolerated for active members of
the array, but ZFS would prevent replacement of a vdev with
another identical device because it now appears that the smaller
allocation size required by the pool is not supported by the new
device.
2) The device's physical block size may be too large to be supported
by ZFS. The optimal allocation size for the vdev may be quite
large. For example, a RAID controller may export a vdev that
requires read-modify-write cycles unless accessed using 64k
aligned/sized requests. ZFS currently has an 8k minimum block
size limit.
Reporting both the logical and physical allocation sizes for vdevs
solves these problems. A device may be used so long as the logical
block size is compatible with the configuration. By comparing the
logical and physical block sizes, new configurations can be optimized
and administrators can be notified of any existing pools that are
sub-optimal.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/spa.h:
Add the SPA_ASHIFT constant. ZFS currently has a hard upper
limit of 13 (8k) for ashift and this constant is used to
both document and enforce this limit.
sys/cddl/contrib/opensolaris/uts/common/sys/fs/zfs.h:
Add the VDEV_AUX_ASHIFT_TOO_BIG error code.
Add fields for exporting the configured, logical, and
physical ashift to the vdev_stat_t structure.
Add VDEV_STAT_VALID() macro which can be used to verify the
presence of required vdev_stat_t fields in nvlist data.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c:
Provide a SYSCTL_PROC handler for "max_auto_ashift". Since
the limit is only referenced long after boot when a create
operation occurs, there's no compelling need for it to be
a boot time configurable tunable. This also allows the
validation code for the max_auto_ashift value to be contained
within the sysctl handler.
Populate the new fields in the vdev_stat_t structure.
Fail vdev opens if the vdev reports an ashift larger than
SPA_MAXASHIFT.
Propogate vdev_logical_ashift and vdev_physical_ashift between
child and parent vdevs as is done for vdev_ashift.
In vdev_open(), restore code that fails opens for devices
where vdev_ashift grows. This can only happen now if the
device's logical ashift grows, which means it really isn't
safe to use the device.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/vdev_impl.h:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_file.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_mirror.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_missing.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_raidz.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_root.c:
Update the vdev_open() API so that both logical (what was
just ashift before) and physical ashift are reported.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/vdev_impl.h:
Add two new fields, vdev_physical_ashift and vdev_logical_ashift,
to vdev_t.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa_config.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c:
Add vdev_ashift_optimize(). Call it anytime a new top-level
vdev is allocated.
cddl/contrib/opensolaris/cmd/zpool/zpool_main.c:
Add text for the VDEV_AUX_ASHIFT_TOO_BIG error.
For each sub-optimally configured leaf vdev, report configured
and native block sizes.
cddl/contrib/opensolaris/cmd/zpool/zpool_main.c:
cddl/contrib/opensolaris/lib/libzfs/common/libzfs.h:
cddl/contrib/opensolaris/lib/libzfs/common/libzfs_status.c:
Introduce a new zpool status: ZPOOL_STATUS_NON_NATIVE_ASHIFT.
This status is reported on healthy pools containing vdevs
configured to use a block size smaller than their reported
physical block size.
cddl/contrib/opensolaris/lib/libzfs/common/libzfs_status.c:
Update find_vdev_problem() and supporting functions to
provide the full vdev_stat_t structure to problem checking
routines, and to allow decent into replacing vdevs.
Add a vdev_non_native_ashift() validator which is used on
the full vdev tree to check for ZPOOL_STATUS_NON_NATIVE_ASHIFT.
cddl/contrib/opensolaris/lib/libzpool/common/kernel.c:
cddl/contrib/opensolaris/lib/libzpool/common/sys/zfs_context.h:
Enhance sysctl userland stubs now that a SYSCTL_PROC handler
is used in vdev.c.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/metaslab.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/metaslab_impl.h:
When the group membership of a metaslab class changes (i.e.
when a vdev is added or removed from a pool), walk the group
list to determine the smallest block size currently available
and record this in the metaslab class.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/metaslab.h:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/metaslab.c:
Add the metaslab_class_get_minblocksize() accessor.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio_compress.h:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zio_compress.c:
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c:
In zio_compress_data(), take the minimum blocksize as an
input parameter instead of assuming SPA_MINBLOCKSIZE.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c:
In l2arc_compress_buf(), pass SPA_MINBLOCKSIZE as the minimum
blocksize of the device. The l2arc code performs has it's own
code for deciding if compression is worth while, so this
effectively disables zio_compress_data() from second guessing
the original decision.
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zio.c:
In zio_write_bp_init(), use the minimum blocksize of the
normal metaslab class when compressing data.
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