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diff --git a/man/lvconvert.8_des b/man/lvconvert.8_des new file mode 100644 index 0000000..1bc3dfa --- /dev/null +++ b/man/lvconvert.8_des @@ -0,0 +1,71 @@ +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. +.P +To display the current LV type, run the command: +.P +.B lvs -o name,segtype +.I LV +.P +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. +.P +Sub LVs can be displayed with the command: +.P +.B lvs -a +.P +The +.B linear +type is equivalent to the +.B striped +type when one stripe exists. +In that case, the types can sometimes be used interchangeably. +.P +In most cases, the +.B mirror +type is deprecated and the +.B raid1 +type should be used. They are both implementations of mirroring. +.P +Striped raid types are +\fBraid0/raid0_meta\fP, +\fBraid5\fP (an alias for raid5_ls), +\fBraid6\fP (an alias for raid6_zr) and +\fBraid10\fP (an alias for raid10_near). +.P +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 +\fBlvmraid\fP(7) for more information. +.P +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). +.P +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). +.P +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. +.P +Striped raid types support converting the layout, their stripesize and +their number of stripes. +.P +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. |