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followup: some clarifcations, small aditions

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
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Thomas Lamprecht 1 month ago
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51e544b624
1 changed files with 8 additions and 8 deletions
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      local-zfs.adoc

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local-zfs.adoc View File

@@ -441,11 +441,11 @@ pool is used to store metadata, deduplication tables, and optionally small
file blocks.

A `special` device can improve the speed of a pool consisting of slow spinning
hard disks with a lot of changing metadata. For example workloads that involve
creating or deleting a large number of files will benefit from the presence of
a `special` device. ZFS datasets can be configured to store whole small files
on the `special` device which can further improve the performance. Use SSDs for
the `special` device.
hard disks with a lot of metadata changes. For example workloads that involve
creating, updating or deleting a large number of files will benefit from the
presence of a `special` device. ZFS datasets can also be configured to store
whole small files on the `special` device which can further improve the
performance. Use fast SSDs for the `special` device.

IMPORTANT: The redundancy of the `special` device should match the one of the
pool, since the `special` device is a point of failure for the whole pool.
@@ -466,14 +466,14 @@ two in the range between `512B` to `128K`. After setting the property new file
blocks smaller than `size` will be allocated on the `special` device.

IMPORTANT: If the value for `special_small_blocks` is greater than or equal to
the `recordsize` of the dataset, *all* data will be written to the `special`
device, so be careful!
the `recordsize` (default `128K`) of the dataset, *all* data will be written to
the `special` device, so be careful!

Setting the `special_small_blocks` property on a pool will change the default
value of that property for all child ZFS datasets (for example all containers
in the pool will opt in for small file blocks).

.Opt in for small file blocks pool-wide:
.Opt in for all file smaller than 4K-blocks pool-wide:

zfs set special_small_blocks=4K <pool>


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