ZFS CoW and Ceph CoW and CSI (by quqi99)

古城微笑少年丶 2022-11-04 08:20 157阅读 0赞

**作者：张华 发表于：2021-03-08  
版权声明：可以任意转载，转载时请务必以超链接形式标明文章原始出处和作者信息及本版权声明**

## ZFS Basic Usage ##

sudo apt install zfsutils-linux
    #sudo zpool create new-pool /dev/sdb /dev/sdc         #striped pool, raid-0
    #sudo zpool create new-pool mirror /dev/sdb /dev/sdc  #mirrored pool, raid-1
    sudo zpool create -m /usr/share/pool new-pool mirror /dev/sdb /dev/sdc #-m is mount point
    sudo zpool add new-pool /dev/sdx
    sudo zpool status
    zfs list
    sudo zpool destroy new-pool
    sudo zfs snapshot <pool-id>
    sudo zfs rollback <pool-id>

## ZFS CoW Test ##

使用vim或rsync修改ZFS上的文件会导制整个文件重新写入，以CoW写入 (ZFS是文件系统级别CoW, Ceph是块级别Cow)

sudo apt install zfs -y && sudo /sbin/modprobe zfs
    dd if=/dev/zero of=/tmp/disk0  bs=1M  count=100
    sudo zpool create testpool /tmp/disk0
    sudo zfs create testpool/sdc
    sudo zfs get recordsize testpool/sdc
    sudo cp ~/.vimrc /testpool/sdc/vimrc
    $ ls -i /testpool/sdc/
    256 vimrc
    $ zdb -ddddd testpool/sdc 256
    ...
    Indirect blocks:
                   0 L0 0:4ae00:3800 3800L/3800P F=1 B=152/152 cksum=52e2222c06f:25cf8696e8501d:b54096cb07913e1f:d6eba6a36d42e991
    
    zdb -R testpool 0:4ae00:3800:r > /tmp/file
    $ diff /tmp/file /testpool/sdc/vimrc 
    459d458
    < 
    \ No newline at end of file
    
    echo 'modify vimrc' |sudo tee -a /testpool/sdc/vimrc
    $ ls -i /testpool/sdc/vimrc 
    256 /testpool/sdc/vimrc
    $ zdb -ddddd testpool/sdc 256
    0 L0 0:69e00:3800 3800L/3800P F=1 B=189/189 cksum=52f651a16b5:25cf8cebaf016b:b54096de7b2dc560:d6eba6d2669c6ef3
    
    zdb -R testpool 0:4ae00:3800:r > /tmp/file_old
    zdb -R testpool 0:69e00:3800:r　> /tmp/file_new
    #vimdiff /tmp/file_old /tmp/file2
    $ diff /tmp/file_old /tmp/file_new
    459c459,462
    < 
    \ No newline at end of file
    ---
    > modify vimrc
    
    
    sudo cp /testpool/sdc/vimrc /tmp/vimrc
    echo 'xxxxxxxxx' |sudo tee -a /tmp/vimrc
    $ sudo rsync -av --inplace --no-whole-file /tmp/vimrc /testpool/sdc/vimrc
    sending incremental file list
    vimrc
    sent 506 bytes  received 161 bytes  1,334.00 bytes/sec
    total size is 14,335  speedup is 21.49
    $ zdb -ddddd testpool/sdc 256
    ...
    0 L0 0:84e00:3800 3800L/3800P F=1 B=318/318 cksum=53056157fa5:25cf8f4613d2d3:b54096e2b7747740:d6eba6d8fd3d794b
    zdb -R testpool 0:84e00:3800:r > /tmp/file_after_rsync_replace

## Ceph CoW Test ##

ceph snapshot是把源volume基于CoW做一个只读副本，以后用于恢复。  
ceph clone可以基于snapshot来做clone, 也是基于CoW。即基于snapshot的clone只创建了映射到源(这里是快照)的逻辑，没有给clone分配真实的物理空间。虽然快照是只读的，但是基于快照创建的克隆是可读可写的。当我们给clone的镜像写操作时系统才会真正的给clone的镜像分配物理空间。明白了上面的道理所以我们知道从快照克隆的镜像时依赖于快照的，一旦快照被删除则这个克隆镜像也就毁了，所以我们要保护好这个快照。

./generate-bundle.sh --ceph --name k8s --create-model --run
    juju scp kubernetes-master/0:config ~/.kube/config
    juju ssh ceph-mon/0 -- sudo -s
    ceph -s
    ceph df
    ceph osd tree
    ceph osd lspools  #rados lspools
    rbd ls <pool>
    
    sudo modprobe rbd
    #pg_num=128(<5 OSDs), pg_num=512(5~10 OSDs), pg_num=4096(10~50 OSDs)
    # pg_num(https://ceph.com/pgcalc/) (> 50 OSDs)
    ceph osd pool create testpool 128
    sudo rbd create --size 1 -p testpool test1
    sudo rbd ls testpool
    sudo rbd info testpool/test1
    
    #create snap
    sudo rbd snap create testpool/test1@test1-snap
    # sudo rbd snap list testpool/test1
    SNAPID  NAME        SIZE   PROTECTED  TIMESTAMP               
         4  test1-snap  1 MiB             Mon Mar  8 02:57:24 2021
    
    # create clone
    sudo rbd snap protect testpool/test1@test1-snap
    sudo rbd clone testpool/test1@test1-snap testpool/test1-snap-clone
    sudo rbd snap unprotect testpool/test1@test1-snap
    #sudo rbd snap rm testpool/test1@test1-snap
    # sudo rbd ls testpool
    test1
    test1-snap-clone
    # sudo rbd info testpool/test1-snap-clone |grep parent
            parent: testpool/test1@test1-snap
    
    #如果不想被依赖于快照，需要对克隆和快照做一个合并
    sudo rbd flatten testpool/test1-snap-clone
    # sudo rbd info testpool/test1-snap-clone |grep parent
    #

## k8s使用ceph-csi消费RBD作为持久化存储 ##

#set up ceph k8s env
    ./generate-bundle.sh --ceph --name k8s --create-model --run
    juju scp kubernetes-master/0:config ~/.kube/config
    
    charm yaml已经帮助部署了ceph-csi(git clone https://github.com/ceph/ceph-csi.git), 如果重头开始搭建见：
    K8S使用ceph-csi持久化存储之RBD - https://mp.weixin.qq.com/s?__biz=MzAxMjk0MTYzNw==&mid=2247484067&idx=1&sn=43bdeb61540c088035d798ee42bbd076

## k8s使用ceph-csi持久化存储之CephFS ##

k8s也可以在块的基础上来使用FS, 见 - https://www.cnblogs.com/wsjhk/p/13710577.html

## k8s CSI插件开发 ##

k8s CSI插件开发导读见 - https://www.jianshu.com/p/88ec8cba7507

ZFS CSI Driver - https://github.com/openebs/zfs-localpv  
Ceph CSI Driver - https://github.com/ceph/ceph-csi

ZFS基于文件级实现CoW, Ceph基于块级实现CoW.

ZFS CSI Driver（https://github.com/openebs/zfs-localpv/blob/master/pkg/driver/controller.go）实现了Volume, Snap等生命周期管理的方法。

*  CreateZFSVolume
 *  CreateSnapClone

Ceph CSI Driver 不仅实现了Volume, Snap的生命周期管理，也实现了Clone的生命周期管理，所以理论上Ceph CSI Driver也是支持CoW的。见：  
https://github.com/ceph/ceph-csi/blob/devel/internal/rbd/clone.go  
https://github.com/ceph/ceph-csi/blob/devel/internal/rbd/driver.go

## Reference ##

\[1\] https://ubuntu.com/tutorials/setup-zfs-storage-pool\#2-installing-zfs  
\[2\] http://tim-tang.github.io/blog/2016/06/05/zfs-cow-deepin  
\[3\] https://my.oschina.net/wangzilong/blog/1595081