[pve-devel] [PATCH docs 1/2] Expand documentation for swap with ZFS.

[Stoiko Ivanov]

and add an anchor for referencing in pve-installation.adoc

Signed-off-by: Stoiko Ivanov <***@proxmox.com>
---
local-zfs.adoc | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/local-zfs.adoc b/local-zfs.adoc
index a5d2fc1..13f6050 100644
--- a/local-zfs.adoc
+++ b/local-zfs.adoc
@@ -307,14 +307,18 @@ time this value changes:
====


+[[zfs_swap]]
.SWAP on ZFS

-SWAP on ZFS on Linux may generate some troubles, like blocking the
+Swap-space created on a zvol may generate some troubles, like blocking the
server or generating a high IO load, often seen when starting a Backup
to an external Storage.

We strongly recommend to use enough memory, so that you normally do not
-run into low memory situations. Additionally, you can lower the
+run into low memory situations. Should you need or want to add swap, it is
+preferred to create a partition on a physical disk and use it as swapdevice.
+You can leave some space free for this purpose in the advanced options of the
+installer. Additionally, you can lower the
``swappiness'' value. A good value for servers is 10:

sysctl -w vm.swappiness=10

[Stoiko Ivanov]

Additionally add a note that no swap is created when ZFS is selected.

Signed-off-by: Stoiko Ivanov <***@proxmox.com>
---
pve-installation.adoc | 42 ++++++++++++++++++++++++++++++++++++++----
1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/pve-installation.adoc b/pve-installation.adoc
index d27184c..0c05384 100644
--- a/pve-installation.adoc
+++ b/pve-installation.adoc
@@ -94,10 +94,11 @@ defaults to `ext4`. The installer uses LVM if you select `ext3`,
`ext4` or `xfs` as file system, and offers additional option to
restrict LVM space (see <<advanced_lvm_options,below>>)

-If you have more than one disk, you can also use ZFS as file system.
-ZFS supports several software RAID levels, so this is specially useful
-if you do not have a hardware RAID controller. The `Options` button
-lets you select the ZFS RAID level, and you can choose disks there.
+You can also use ZFS as file system. ZFS supports several software RAID
+levels, so this is specially useful if you do not have a hardware RAID
+controller. The `Options` button lets you select the ZFS RAID level, and
+you can choose disks there. Additionally you can set additional options (see
+<<advanced_zfs_options,below>>).

[thumbnail="screenshot/pve-select-location.png", float="left"]

@@ -204,6 +205,39 @@ will be used.
NOTE: LVM requires free space in the VG for snapshot creation (not
required for lvmthin snapshots).

+[[advanced_zfs_options]]
+Advanced ZFS Configuration Options
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The installer creates a ZFS pool `rpool`. When selecting ZFS, no swap space is
+created by default. You can leave some unpartitioned space for swap or create
+a swap zvol after installation, though the latter can lead to problems
+(see <<zfs_swap,ZFS swap notes>>).
+
+`ashift`::
+
+Defines the `ashift` value for the created pool. The `ashift` needs
+to be set at least to the sector-size of the underlying disks (2 to
+the power of `ashift` is the sector-size), or any disk,
+which might be put in the pool (e.g. during replacing a defective disk).
+
+`compress`::
+
+Defines whether compression is enabled for `rpool`.
+
+`checksum`::
+
+Defines which checksumming algorithm should be used for `rpool`.
+
+`copies`::
+
+Defines the `copies` parameter for `rpool`. Check the `zfs(8)` manpage for the
+semantics, and why this does not replace redundancy on disk-level.
+
+`hdsize`::
+
+Defines the total HD size to be used. This way you can save free
+space on the HD for further partitioning (e.g. for creating a swap-partition).
+

ZFS Performance Tips
~~~~~~~~~~~~~~~~~~~~

[Dietmar Maurer]

applied