AIX LVM Howto

Initial LVM howto - bits of practical knowledge

How many free space is available in a particular VG?

$ lsvg rootvg

VOLUME GROUP:       rootvg                   VG IDENTIFIER:  005529fc00004c000000012aee01c41b

VG STATE:           active                   PP SIZE:        64 megabyte(s)

VG PERMISSION:      read/write               TOTAL PPs:      1094 (70016 megabytes)

MAX LVs:            256                      FREE PPs:       330 (21120 megabytes)

LVs:                18                       USED PPs:       764 (48896 megabytes)

OPEN LVs:           17                       QUORUM:         1 (Disabled)

TOTAL PVs:          2                        VG DESCRIPTORS: 3

STALE PVs:          0                        STALE PPs:      0

ACTIVE PVs:         2                        AUTO ON:        yes

MAX PPs per VG:     32512

MAX PPs per PV:     1016                     MAX PVs:        32

LTG size (Dynamic): 256 kilobyte(s)          AUTO SYNC:      no

HOT SPARE:          no                       BB POLICY:      relocatable

PV RESTRICTION:     none

So you have TOTAL PPs: 1094 (70016 megabytes) = 70GB total and FREE PPs: 330 (21120 megabytes) =20GB free in this volume group, rootvg.

The actual usable amount is determined by mirroring.

$ lsvg -l rootvg

rootvg:

LV NAME             TYPE       LPs     PPs     PVs  LV STATE      MOUNT POINT

hd5                 boot       1       2       2    closed/syncd  N/A

hd6                 paging     32      64      2    open/syncd    N/A

hd8                 jfs2log    1       2       2    open/syncd    N/A

hd4                 jfs2       4       8       2    open/syncd    /

hd2                 jfs2       32      64      2    open/syncd    /usr

hd9var              jfs2       16      32      2    open/syncd    /var

hd3                 jfs2       4       8       2    open/syncd    /tmp

hd1                 jfs2       4       8       2    open/syncd    /home

hd10opt             jfs2       8       16      2    open/syncd    /opt

Taking a look at LP -> PP proportions, you may say that every LV (under every FS) has two copies.

Mirroring is defined per LV, not for the whole VG.

You have:

- 20GB of free space for an unmirrored new LV, or

- 10GB of free space if you want to keep the new LV mirrored, or

- 10GB for extending existing mirrored LVs (= filesystems).

Should you have to increase anything by PPs (physical partitons) - for example, paging space with chps - , refer to 'PP SIZE' in the lsvg output.

Which VG contains my filesystem?

lsvg | lsvg -il

should give a listing of every LV/FS known to AIX at the moment.

If you go from the filesystem toward the VG, these are the required steps:

df /myfs or lsfs /myfs -> get the LV name

lslv mylv (without /dev/) -> get the VG name

See also: lsvgfs

What size are my disks?

$ lsvg -p rootvg

rootvg:

PV_NAME           PV STATE          TOTAL PPs   FREE PPs    FREE DISTRIBUTION

hdisk0            active            547         165         00..00..00..55..110

hdisk1            active            547         165         00..00..00..55..110

You need to know the PP size defined for the VG. Here, 547 PPs of 64MB make up the 36GB PVs (disks).

The PP size of the rootvg is defined automatically during installation.

The (deprecated) bootinfo command can be used for any disk, including those not belonging to any VG:

bootinfo -s hdisk0

Parameters

Sorry about the look, I will try to improve it later.

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Is a certain filesystem in frozen state?

Freezing a JFS2 filesystem works this way:

chfs -a freeze=120 /freeze

The fsdb utility shows the FM_CLEANQUIESCED flag with the 'su(perblock)' command:

> su

[1] s_magic:            'J2FS'          [18] s_fscklog:         1

[2] s_version:          2               [19] s_fsckloglen:      50

[3] s_size:     0x000000000007fe58      [20] s_bsize:           4096

[4] s_logdev:   0x8000000a00000003      [21] s_logserial:       0x0000000d

[5] s_l2bsize:          12              [22] s_logpxd.len:      0

[6] s_l2bfactor:        3               [23] s_logpxd.addr1:    0x00

[7] s_pbsize:           512             [24] s_logpxd.addr2:    0x00000000

[8] s_l2pbsize:         9                    s_logpxd.address:  0

[9] s_rsv:              Not Displayed   [25] s_fsckpxd.len:     53

[10] s_agsize:          0x00002000      [26] s_fsckpxd.addr1:   0x00

[11] s_flag:            0x00000100      [27] s_fsckpxd.addr2:   0x0000ffcb

                                             s_fsckpxd.address: 65483

                                        [28] s_ait.len:         4

  J2_GROUPCOMMIT                        [29] s_ait.addr1:       0x00

                                        [30] s_ait.addr2:       0x0000000b

                                             s_ait.address:     11

[12] s_state:           0x00001001      [31] s_fpack:           'freeze'

        FM_MOUNT  FM_CLEANQUIESCED              [32] s_fname:           ''

[13] s_time.tj_sec: 0x0000000050a674c0  [33] s_time.tj_nsec:    0x00000000

[14] s_ait2.len:        4               [34] s_xfsckpxd.len:    0

[15] s_ait2.addr1:      0x00            [35] s_xfsckpxd.addr1:  0x00

[16] s_ait2.addr2:      0x0000001d      [36] s_xfsckpxd.addr2:  0x00000000

     s_ait2.address:    29                  s_xfsckpxd.address: 0

[17] s_xsize: 0x0000000000000000        [37] s_xlogpxd.len:     0

[40] feature_compat: 0x0000000000000001 [38] s_xlogpxd.addr1:   0x00

[41] feature_rdonly: 0x0000000000000000 [39] s_xlogpxd.addr2:   0x00000000

[42] feature_incompat: 0x0000000000000000    s_xlogpxd.address: 0

[43-49] <...snapshot info...>           [50] s_maxext:  0x00000000

So, to detect this, here is an example:

# echo "su\n" | fsdb /freeze 2>&1 | grep -q FM_CLEANQUIESCED && echo "FS is frozen"

There is a new errpt enrty logged each time a filesystem freeze period expires:

LABEL:          J2_FREEZE_TIMEOUT

IDENTIFIER:     86CA9D0C

Class:           O

Type:            INFO

Resource Name:   SYSJ2

Description

FILE SYSTEM FREEZE TIMEOUT EXPIRED. FILE SYSTEM IS THAWED.

Probable Causes

FREEZE TIMEOUT REQUESTED TOO SHORT

Detail Data

JFS2 MAJOR/MINOR DEVICE NUMBER

000A 000B

FILE SYSTEM DEVICE AND MOUNT POINT

/dev/freezelv, /freeze

Manage mirror pools

Mirror pools provide an efficient method of separating LUNs from different sides of a redundant storage.

Things like running cfgmgr, identifying disks and sizes etc are not mentioned here.

Make sure you adjust disk parameters before assigning them to VGs because most of them requires re-initialization of disks (rmdev/mkdev).

Make sure you record LUN IDs for the storage admins before removing them.

I assume that new disk devices are available.

Example: "myvg" with 2x3 LUNs in VG mirror, migrated to 2x1 LUNs. Pool names speak for themselves.

Pool layout

# lsvg -P myvg

Physical Volume   Mirror Pool

hdisk1        oldpool1

hdisk2        oldpool2

hdisk3        oldpool1

hdisk4        oldpool2

hdisk5        oldpool1

hdisk6        oldpool2

You can have a maximum of 3 pools at once. Add newpool1 and build 3rd mirror copy.

# extendvg -p newpool1 myvg hdisk101

# mirrorvg -S -c 3 -p copy1=oldpool1 -p copy2=oldpool2 -p copy3=newpool1 myvg hdisk101

Check if mirroring has finished (STALE PPs should be 0)

# lsvg myvg | grep STALE

Remove oldpool1 disks

# unmirrorvg -c 2 myvg hdisk1 hdisk3 hdisk5

# reducevg myvg hdisk1 hdisk3 hdisk5

# for d in hdisk1 hdisk3 hdisk5; do rmdev -dl $d; done

Repeat for newpool2 and oldpool2

# extendvg -p newpool2 myvg hdisk201

# mirrorvg -S -c 3 -p copy1=oldpool2 -p copy2=newpool1 -p copy3=newpool2 myvg hdisk201

# lsvg myvg | grep STALE

# unmirrorvg -c 2 myvg hdisk2 hdisk4 hdisk6

# reducevg myvg hdisk2 hdisk4 hdisk6

# for d in hdisk2 hdisk4 hdisk6; do rmdev -dl $d; done

Resulting layout

# lsvg -P myvg

Physical Volume   Mirror Pool

hdisk101    newpool1

hdisk201    newpool2

Low level command flags

lqueryvg -g -c VG's number of disks

lqueryvg -g -n VG's number of LVs

lqueryvg -g -P VG's PVIDs

lqueryvg -g -s/S? PP size

getlvodm –C (lspv)

getlvodm -e LV name

getlvodm -m LV mount point

getlvodm -y LV type

getlvodm -c LV copies

getlvodm -N stripped or not

getlvodm -v VGID

getlvodm -g name of (one) PV

getlvodm -L all LVs/LVIDs of a VG

getlvcb -AT all information about the LV

getlvcb -a intrA-physical volume allocation policy

getlvcb -c copies

getlvcb -f file system name

getlvcb –L label

getlvcb -r inteR-physical volume allocation policy

getlvcb –P stripe expn

getlvcb –S striping width

getlvcb -s strictness

getlvcb –t type of filesystem

getlvcb –u upper limit

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