對於一個存儲，不可避免的會遇到擴容、縮減存儲容量的問題。

1 為Glusterfs擴容

提前準備好了一個gluster volume:

[[email protected] ~]# gluster volume info repvol
 
Volume Name: repvol
Type: Replicate
Volume ID: 7015b7fe-8039-4d5d-b698-e8321df5289c
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x 2 = 2
Transport-type: tcp
Bricks:
Brick1: node01.lab.example.com:/bricks/thinvol1/brick
Brick2: node02.lab.example.com:/bricks/thinvol1/brick
Options Reconfigured:
performance.stat-prefetch: off
storage.batch-fsync-delay-usec: 0
server.allow-insecure: on
performance.readdir-ahead: on
transport.address-family: inet
nfs.disable: on

可以看出repvol是一個包含2個brick的1x2復制卷，將repvol掛載到node02 server上，並寫入一些數據以作測試。

[[email protected] ~]# mount -t cifs //node01.lab.example.com/gluster-repvol -o user=smbuser,pass=redhat /mnt

[[email protected] ~]# cd /mnt
[[email protected] mnt]# ls
[[email protected] mnt]# touch {1..100}.file

使用如下命令為repvol再增加兩個brick

[[email protected] ~]# gluster volume add-brick repvol node01.lab.example.com:/bricks/thinvol2/brick node02.lab.example.com:/bricks/thinvol2/brick
volume add-brick: success

[[email protected] ~]# gluster volume info repvol
 
Volume Name: repvol
Type: Distributed-Replicate
Volume ID: 7015b7fe-8039-4d5d-b698-e8321df5289c
Status: Started
Snapshot Count: 0
Number of Bricks: 2 x 2 = 4
Transport-type: tcp
Bricks:
Brick1: node01.lab.example.com:/bricks/thinvol1/brick
Brick2: node02.lab.example.com:/bricks/thinvol1/brick
Brick3: node01.lab.example.com:/bricks/thinvol2/brick
Brick4: node02.lab.example.com:/bricks/thinvol2/brick
Options Reconfigured:
performance.stat-prefetch: off
storage.batch-fsync-delay-usec: 0
server.allow-insecure: on
performance.readdir-ahead: on
transport.address-family: inet
nfs.disable: on

可以看到repvol已經變成了一個2x2的分布式復制卷，擴容後我們還需要把原有的數據rebalance

[[email protected] ~]# gluster volume rebalance repvol start
volume rebalance: repvol: success: Rebalance on repvol has been started successfully. Use rebalance status command to check status of the rebalance process.
ID: a8fba779-6c2d-449b-8847-58aeb2ae1798

[[email protected] ~]# gluster volume rebalance repvol status
                                    Node Rebalanced-files          size       scanned      failures       skipped               status  run time in h:m:s
                               ---------      -----------   -----------   -----------   -----------   -----------         ------------     --------------
                               localhost               48        0Bytes           100             0             0            completed        0:0:5
                                  node02                0        0Bytes             0             0             0            completed        0:0:2
volume rebalance: repvol: success

這裏有一個需要註意的地方，當數據量太大的時候，對數據進行rebalance必須要考慮的一個問題就是性能，不能因為數據rebalance而影響我們的存儲的正常使用。Glusterfs也考慮到了這個問題，在進行數據rebalance時，根據實際場景不同設計了三種不同的“級別”：

1）lazy：每次僅可以遷移一個文件
2）normal:默認設置，每次遷移2個文件或者是(CPU邏輯個數-4)/2,哪個大，選哪個
3）aggressive:每次遷移4個文件或者是(CPU邏輯個數-4)/2

通過以下命令進行配置：

gluster volume set VOLUME-NAME cluster.rebal-throttle [lazy|normal|aggressive]

如將volume repvol設置為lazy

[[email protected] ~]# gluster volume set repvol cluster.rebal-throttle lazy
volume set: success

2 縮減volume大小

將我們剛剛添加的2個brick再從volume repovl中刪掉

[[email protected] ~]# gluster volume remove-brick repvol node01.lab.example.com:/bricks/thinvol2/brick node02.lab.example.com:/bricks/thinvol2/brick start
volume remove-brick start: success
ID: db72aaf8-e60d-4e56-be60-54469df9c233

[[email protected] ~]# gluster volume remove-brick repvol node01.lab.example.com:/bricks/thinvol2/brick node02.lab.example.com:/bricks/thinvol2/brick status
                                    Node Rebalanced-files          size       scanned      failures       skipped               status  run time in h:m:s
                               ---------      -----------   -----------   -----------   -----------   -----------         ------------     --------------
                               localhost               48        0Bytes           101             0             0            completed        0:0:3
                                  node02                0        0Bytes             0             0             0            completed        0:0:1

[[email protected] ~]# gluster volume remove-brick repvol node01.lab.example.com:/bricks/thinvol2/brick node02.lab.example.com:/bricks/thinvol2/brick commit
Removing brick(s) can result in data loss. Do you want to Continue? (y/n) y
volume remove-brick commit: success
Check the removed bricks to ensure all files are migrated.
If files with data are found on the brick path, copy them via a gluster mount point before re-purposing the removed brick.

此時再看repvol已經重新變為1x2的復制卷了

[[email protected] ~]# gluster volume info repvol
 
Volume Name: repvol
Type: Replicate
Volume ID: 7015b7fe-8039-4d5d-b698-e8321df5289c
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x 2 = 2
Transport-type: tcp
Bricks:
Brick1: node01.lab.example.com:/bricks/thinvol1/brick
Brick2: node02.lab.example.com:/bricks/thinvol1/brick
Options Reconfigured:
cluster.rebal-throttle: lazy
performance.stat-prefetch: off
storage.batch-fsync-delay-usec: 0
server.allow-insecure: on
performance.readdir-ahead: on
transport.address-family: inet
nfs.disable: on

[[email protected] ~]# ls /bricks/thinvol1/brick/ | wc -w
100

本文出自 “不積跬步，無以至千裏” 博客，請務必保留此出處http://jiaxiaolei.blog.51cto.com/3117381/1951535

Glusterfs 擴容、縮減