diff --git a/man/lvconvert.8_des b/man/lvconvert.8_des index dc51aaede..6fd1ed9cd 100644 --- a/man/lvconvert.8_des +++ b/man/lvconvert.8_des @@ -7,6 +7,17 @@ To display the current LV type, run the command: .B lvs -o name,segtype .I 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: + +.B lvs -a + The .B linear type is equivalent to the @@ -20,45 +31,41 @@ type is deprecated and the .B raid1 type should be used. They are both implementations of mirroring. -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. - Striped raid types are -.B raid0/raid0_meta -, -.B raid5 -(an alias for raid5_ls), -.B raid6 -(an alias for raid6_zr) and -.B raid10 -(an alias for raid10_near). +\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). 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 blocks for performance -reasons thus avoiding contention on a single device. Layouts of raid5 rotating -parity blocks can be one of 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. Any \"_n\" layouts allow for conversion between -raid levels (raid5_n -> raid6 or raid5_n -> striped/raid0/raid0_meta). -raid6 layouts are zero-restart (raid6_zr with alias raid6), next-restart (raid6_nr), -next-continue (raid6_nc). 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. +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. -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. +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). -Sub LVs can be displayed with the command -.B lvs -a +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. diff --git a/man/lvcreate.8_des b/man/lvcreate.8_des index 42f42135d..589bd6307 100644 --- a/man/lvcreate.8_des +++ b/man/lvcreate.8_des @@ -1,8 +1,8 @@ lvcreate creates a new LV in a VG. For standard LVs, this requires allocating logical extents from the VG's free physical extents. If there -is not enough free space, then the VG can be extended (see -\fBvgextend\fP(8)) with other PVs, or existing LVs can be reduced or -removed (see \fBlvremove\fP, \fBlvreduce\fP.) +is not enough free space, the VG can be extended with other PVs +(\fBvgextend\fP(8)), or existing LVs can be reduced or removed +(\fBlvremove\fP(8), \fBlvreduce\fP(8).) To control which PVs a new LV will use, specify one or more PVs as position args at the end of the command line. lvcreate will allocate @@ -19,7 +19,7 @@ unique PVs be available in the VG for allocation. Thin pools (for thin provisioning) and cache pools (for caching) are represented by special LVs with types thin-pool and cache-pool (see \fBlvmthin\fP(7) and \fBlvmcache\fP(7)). The pool LVs are not usable as -standard block devices, but the LV names act references to the pools. +standard block devices, but the LV names act as references to the pools. Thin LVs are thinly provisioned from a thin pool, and are created with a virtual size rather than a physical size. A cache LV is the combination of @@ -27,10 +27,9 @@ a standard LV with a cache pool, used to cache active portions of the LV to improve performance. .SS Usage notes In the usage section below, \fB--size\fP \fISize\fP can be replaced -with \fB--extents\fP \fINumber\fP. See both descriptions -the options section. +with \fB--extents\fP \fINumber\fP. See descriptions in the options section. In the usage section below, \fB--name\fP is omitted from the required -options, even though it is typically used. When the name is not +options, even though it is typically used. When the name is not specified, a new LV name is generated with the "lvol" prefix and a unique -numeric suffix. Also see the description in the options section. +numeric suffix.