105 lines
3.8 KiB
ReStructuredText
105 lines
3.8 KiB
ReStructuredText
Adding new device
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^^^^^^^^^^^^^^^^^
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The unallocated space requirements depend on the selected storage
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profiles. The requirements for the storage profile must be met for the
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selected for both data and metadata (e.g. if you have single data and
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RAID1 metadata, the stricter RAID1 requirements must be met or the
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filesystem may run out of metadata space and go read-only).
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Before adding a drive, make sure there is enough unallocated space on
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existing drives to create new metadata block groups (for filesystems
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over 50GB, this is `1GB * (number_of_devices + 2))`.
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If using a striped profile (`raid0`, `raid10`, `raid5`, or `raid6`), then do a
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full data balance of all data after adding a drive. If adding multiple
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drives at once, do a full data balance after adding the last one.
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.. code-block:: bash
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btrfs balance start -v --full-balance mnt/
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If the balance is interrupted, it can be restarted using the *stripes*
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filter (i.e. `-dstripes=1..N` where *N* is the previous size of the array
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before the new device was added) as long as all devices are the same size.
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If the device sizes are different, a specialized userspace balance tool
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is required. The data balance must be completed before adding any new
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devices or increasing the size of existing ones.
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.. code-block:: bash
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# For going from 4 disk to 5 disks, in Raid 5
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btrfs balance start -v -dstripes=1..4 mnt/
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If you are not using a striped profile now, but intend to convert to a
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striped profile in the future, always perform a full data balance after
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adding drives or replacing existing drives with larger ones. The stock
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*btrfs balance* tool cannot cope with special cases on filesystems with
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striped raid profiles, and will paint itself into a corner that will
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require custom userspace balancing tools to recover if you try.
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To watch one can use the following:
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.. code-block:: bash
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watch "btrfs filesystem usage -T mnt/; btrfs balance status mnt/"
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Convert RAID1 after mkfs with defaults
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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If you forgot to set the block group profile when creating the volume, run the
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following command:
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.. code-block:: bash
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btrfs balance start -v convert=raid1,soft mnt/
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This will convert all remaining profiles that are not yet *raid1*.
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Convert data to RAID10 with RAID1C4 for metadata
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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If you a have multi device setup, or you'd like to have different profiles on a
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single disk, e.g. *RAID10* for data and *RAID1C4* for metadata and system:
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.. code-block:: bash
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btrfs balance start -v -mconvert=raid1C4,soft -dconvert=raid10,soft mnt/
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Compact under used chunks
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^^^^^^^^^^^^^^^^^^^^^^^^^
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If the data chunks are not balanced and used only partially, the *usage* filter
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can be used to make them more compact:
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.. code-block:: bash
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btrfs balance start -v -dusage=10 mnt/
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If the percent starts from a small number, like 5 or 10, the chunks will be
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processed relatively quickly and will make more space available. Increasing the
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percentage can then make more chunks compact by relocating the data.
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Chunks utilized up to 50% can be relocated to other chunks while still freeing
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the space. With utilization higher than 50% the chunks will be basically only
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moved on the devices. The actual chunk layout may help to coalesce the free
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space but this is a secondary effect.
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.. code-block:: bash
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for USAGE in {10..50..10} do
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btrfs balance start -v -dusage=$USAGE mnt/
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done
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Fix incomplete balance
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^^^^^^^^^^^^^^^^^^^^^^
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If the balance is interrupted (due to reboot or cancelled) during conversion to
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RAID1. The following command will skip all RAID1 chunks that have been already
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converted and continue with what's left to convert. Note that an interrupted
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conversion may leave the last chunk under utilized.
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.. code-block:: bash
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btrfs balance start convert=raid1,soft mnt/
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