изменить макет логического тома (Change logical volume layout)
Описание (Description)
lvconvert changes the LV type and includes utilities for LV data
maintenance. The LV type controls data layout and redundancy.
The LV type is also called the segment type or segtype.
To display the current LV type, run the command:
lvs -o name,segtype LV
In some cases, an LV is a single device mapper (dm) layer above
physical devices. In other cases, hidden LVs (dm devices) are
layered between the visible LV and physical devices. LVs in the
middle layers are called sub LVs. A command run on a visible LV
sometimes operates on a sub LV rather than the specified LV. In
other cases, a sub LV must be specified directly on the command
line.
Sub LVs can be displayed with the command:
lvs -a
The linear type is equivalent to the striped type when one stripe
exists. In that case, the types can sometimes be used
interchangably.
In most cases, the mirror type is deprecated and the raid1 type
should be used. They are both implementations of mirroring.
Striped raid types are raid0/raid0_meta, raid5 (an alias for
raid5_ls), raid6 (an alias for raid6_zr) and raid10 (an alias for
raid10_near).
As opposed to mirroring, raid5 and raid6 stripe data and
calculate parity blocks. The parity blocks can be used for data
block recovery in case devices fail. A maximum number of one
device in a raid5 LV may fail, and two in case of raid6. Striped
raid types typically rotate the parity and data blocks for
performance reasons, thus avoiding contention on a single device.
Specific arrangements of parity and data blocks (layouts) can be
used to optimize I/O performance, or to convert between raid
levels. See lvmraid(7) for more information.
Layouts of raid5 rotating parity blocks can be: left-asymmetric
(raid5_la), left-symmetric (raid5_ls with alias raid5), right-
asymmetric (raid5_ra), right-symmetric (raid5_rs) and raid5_n,
which doesn't rotate parity blocks. Layouts of raid6 are: zero-
restart (raid6_zr with alias raid6), next-restart (raid6_nr), and
next-continue (raid6_nc).
Layouts including _n allow for conversion between raid levels
(raid5_n to raid6 or raid5_n to striped/raid0/raid0_meta).
Additionally, special raid6 layouts for raid level conversions
between raid5 and raid6 are: raid6_ls_6, raid6_rs_6, raid6_la_6
and raid6_ra_6. Those correspond to their raid5 counterparts
(e.g. raid5_rs can be directly converted to raid6_rs_6 and vice-
versa).
raid10 (an alias for raid10_near) is currently limited to one
data copy and even number of sub LVs. This is a mirror group
layout, thus a single sub LV may fail per mirror group without
data loss.
Striped raid types support converting the layout, their
stripesize and their number of stripes.
The striped raid types combined with raid1 allow for conversion
from linear → striped/raid0/raid0_meta and vice-versa by e.g.
linear ↔ raid1 ↔ raid5_n (then adding stripes) ↔
striped/raid0/raid0_meta.
