小编给大家分享一下ceph中使用技巧有哪些，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！
1. 设置cephx keys
如果ceph设置了cephx，就可以为不同的用户设置权限。
#创建dummy的key
$ ceph auth get-or-create client.dummy mon 'allow r' osd 'allow rwx pool=dummy'
[client.dummy]
key = AQAPiu1RCMb4CxAAmP7rrufwZPRqy8bpQa2OeQ==
$ ceph auth list
installed auth entries:
...
client.dummy
key: AQAPiu1RCMb4CxAAmP7rrufwZPRqy8bpQa2OeQ==
caps: [mon] allow r
caps: [osd] allow rwx pool=dummy
...
#对dummy的key重新分配权限
$ ceph auth caps client.dummy mon 'allow rwx' osd 'allow rwx pool=dummy'
updated caps for client.dummy
$ ceph auth list
installed auth entries:
client.dummy
key: AQAPiu1RCMb4CxAAmP7rrufwZPRqy8bpQa2OeQ==
caps: [mon] allow rwx
caps: [osd] allow allow rwx pool=dummy/dev/sda2 /srv/ceph/osdX1 xfs rw,noexec,nodev,noatime,nodiratime,barrier=0 0 0
2. 查看rbd被挂载到哪里
由于rbd showmapped只能显示本地挂载的rbd设备，如果机器比较多，而你恰好忘了在哪里map的了，就只能逐个机器找了。利用listwatchers可以解决这个问题。
对于image format为1的块：
$ rbd info boot
rbd image 'boot':
size 10240 MB in 2560 objects
order 22 (4096 kB objects)
block_name_prefix: rb.0.89ee.2ae8944a
format: 1
$ rados -p rbd listwatchers boot.rbd
watcher=192.168.251.102:0/2550823152 client.35321 cookie=1
对于image format为2的块，有些不一样：
[root@osd2 ceph]# rbd info myrbd/rbd1
rbd image 'rbd1':
size 8192 kB in 2 objects
order 22 (4096 kB objects)
block_name_prefix: rbd_data.13436b8b4567
format: 2
features: layering
[root@osd2 ceph]# rados -p myrbd listwatchers rbd_header.13436b8b4567
watcher=192.168.108.3:0/2292307264 client.5130 cookie=1
需要将rbd info得到的序号加到rbd_header后面。
3. 怎样删除巨型rbd image
之前在一些博客看到删除巨型rbd image，如果直接通过rbd rm的话会很耗时（漫长的夜）。但在ceph 0.87上尝试了一下，这个问题已经不存在了，具体过程如下：
#创建一个1PB大小的块
[root@osd2 ceph]# time rbd create myrbd/huge-image -s 1024000000
real 0m0.353s
user 0m0.016s
sys 0m0.009s
[root@osd2 ceph]# rbd info myrbd/huge-image
rbd image 'huge-image':
size 976 TB in 256000000 objects
order 22 (4096 kB objects)
block_name_prefix: rb.0.1489.6b8b4567
format: 1
[root@osd2 ceph]# time rbd rm myrbd/huge-image
Removing image: 2% complete...^\Quit (core dumped)
real 10m24.406s
user 18m58.335s
sys 11m39.507s
上面创建了一个1PB大小的块，也许是太大了，直接rbd rm删除的时候还是很慢，所以用了一下方法：
[root@osd2 ceph]# rados -p myrbd rm huge-image.rbd
[root@osd2 ceph]# time rbd rm myrbd/huge-image
2014-11-06 09:44:42.916826 7fdb4fd5a7e0 -1 librbd::ImageCtx: error finding header: (2) No such file or directory
Removing image: 100% complete...done.
real 0m0.192s
user 0m0.012s
sys 0m0.013s
来个1TB大小的块试试：
[root@osd2 ceph]# rbd create myrbd/huge-image -s 1024000
[root@osd2 ceph]# rbd info myrbd/huge-image
rbd image 'huge-image':
size 1000 GB in 256000 objects
order 22 (4096 kB objects)
block_name_prefix: rb.0.149c.6b8b4567
format: 1
[root@osd2 ceph]# time rbd rm myrbd/huge-image
Removing image: 100% complete...done.
real 0m29.418s
user 0m52.467s
sys 0m32.372s
所以巨型的块删除还是要用以下方法：
format 1：
[root@osd2 ceph]# rbd create myrbd/huge-image -s 1024000000
[root@osd2 ceph]# rbd info myrbd/huge-image
rbd image 'huge-image':
size 976 TB in 256000000 objects
order 22 (4096 kB objects)
block_name_prefix: rb.0.14a5.6b8b4567
format: 1
[root@osd2 ceph]# rados -p myrbd rm huge-image.rbd
[root@osd2 ceph]# time rados -p myrbd ls|grep '^rb.0.14a5.6b8b4567'|xargs -n 200 rados -p myrbd rm
[root@osd2 ceph]# time rbd rm myrbd/huge-image
2014-11-06 09:54:12.718211 7ffae55747e0 -1 librbd::ImageCtx: error finding header: (2) No such file or directory
Removing image: 100% complete...done.
real 0m0.191s
user 0m0.015s
sys 0m0.010s
format 2:
[root@osd2 ceph]# rbd create myrbd/huge-image -s 1024000000 --image-format=2
[root@osd2 ceph]# rbd info myrbd/huge-image
rbd image 'huge-image':
size 976 TB in 256000000 objects
order 22 (4096 kB objects)
block_name_prefix: rbd_data.14986b8b4567
format: 2
features: layering
[root@osd2 ceph]# rados -p myrbd rm rbd_id.huge-image
[root@osd2 ceph]# rados -p myrbd rm rbd_header.14986b8b4567
[root@osd2 ceph]# rados -p myrbd ls | grep '^rbd_data.14986b8b4567' | xargs -n 200 rados -p myrbd rm
[root@osd2 ceph]# time rbd rm myrbd/huge-image
2014-11-06 09:59:26.043671 7f6b6923c7e0 -1 librbd::ImageCtx: error finding header: (2) No such file or directory
Removing image: 100% complete...done.
real 0m0.192s
user 0m0.016s
sys 0m0.010s
注意，如果块是空的，不许要xargs那条语句；如果是非空就需要了。
所以，如果是100TB以上的块，最好还是先删除id，再rbd rm进行删除。
4. 查看kvm或qemu是否支持ceph
$ sudo qemu-system-x86_64 -drive format=?
Supported formats: vvfat vpc vmdk vhdx vdi sheepdog sheepdog sheepdog rbd raw host_cdrom host_floppy host_device file qed qcow2 qcow parallels nbd nbd nbd dmg tftp ftps ftp https http cow cloop bochs blkverify blkdebug
$ qemu-img -h
...
...
Supported formats: vvfat vpc vmdk vhdx vdi sheepdog sheepdog sheepdog rbd raw host_cdrom host_floppy host_device file qed qcow2 qcow parallels nbd nbd nbd dmg tftp ftps ftp https http cow cloop bochs blkverify blkdebug
可以到 http://ceph.com/packages/下载最新的rpm或deb包。
5. 利用ceph rbd配置nfs
一种简单实用的存储方法，具体如下：
#安装nfs rpm
[root@osd1 current]# yum install nfs-utils rpcbind
Loaded plugins: fastestmirror, priorities, refresh-packagekit, security
Loading mirror speeds from cached hostfile
epel/metalink | 5.5 kB 00:00
* base: mirrors.cug.edu.cn
* epel: mirrors.yun-idc.com
* extras: mirrors.btte.net
* rpmforge: ftp.riken.jp
* updates: mirrors.btte.net
Ceph | 951 B 00:00
Ceph-noarch | 951 B 00:00
base | 3.7 kB 00:00
ceph-source | 951 B 00:00
epel | 4.4 kB 00:00
epel/primary_db | 6.3 MB 00:01
extras | 3.4 kB 00:00
rpmforge | 1.9 kB 00:00
updates | 3.4 kB 00:00
updates/primary_db | 188 kB 00:00
69 packages excluded due to repository priority protections
Setting up Install Process
Package rpcbind-0.2.0-11.el6.x86_64 already installed and latest version
Resolving Dependencies
--> Running transaction check
---> Package nfs-utils.x86_64 1:1.2.3-39.el6 will be updated
---> Package nfs-utils.x86_64 1:1.2.3-54.el6 will be an update
--> Finished Dependency Resolution
Dependencies Resolved
======================================================================================================================================
Package Arch Version Repository Size
======================================================================================================================================
Updating:
nfs-utils x86_64 1:1.2.3-54.el6 base 326 k
Transaction Summary
======================================================================================================================================
Upgrade 1 Package(s)
Total download size: 326 k
Is this ok [y/N]: y
Downloading Packages:
nfs-utils-1.2.3-54.el6.x86_64.rpm | 326 kB 00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Updating : 1:nfs-utils-1.2.3-54.el6.x86_64 1/2
Cleanup : 1:nfs-utils-1.2.3-39.el6.x86_64 2/2
Verifying : 1:nfs-utils-1.2.3-54.el6.x86_64 1/2
Verifying : 1:nfs-utils-1.2.3-39.el6.x86_64 2/2
Updated:
nfs-utils.x86_64 1:1.2.3-54.el6
#创建一个块并格式化、挂载
[root@osd1 current]# rbd create myrbd/nfs_image -s 1024000 --image-format=2
[root@osd1 current]# rbd map myrbd/nfs_image
/dev/rbd0
[root@osd1 current]# mkdir /mnt/nfs
[root@osd1 current]# mkfs.xfs /dev/rbd0
log stripe unit (4194304 bytes) is too large (maximum is 256KiB)
log stripe unit adjusted to 32KiB
meta-data=/dev/rbd0 isize=256 agcount=33, agsize=8190976 blks
= sectsz=512 attr=2, projid32bit=0
data = bsize=4096 blocks=262144000, imaxpct=25
= sunit=1024 swidth=1024 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal log bsize=4096 blocks=128000, version=2
= sectsz=512 sunit=8 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
[root@osd1 current]# mount /dev/rbd0 -o rw,noexec,nodev,noatime,nobarrier /mnt/nfs
#改写exports文件，添加一行
[root@osd1 current]# vim /etc/exports
/mnt/nfs 192.168.108.0/24(rw,no_root_squash,no_subtree_check,async)
[root@osd1 current]# exportfs -r
这里还需要执行指令service rpcbind start
[root@osd1 current]# service nfs start
Starting NFS services: [ OK ]
Starting NFS quotas: [ OK ]
Starting NFS mountd: [ OK ]
Starting NFS daemon: [ OK ]
Starting RPC idmapd: [ OK ]
此时客户端就可以挂载了。客户端运行：
showmount -e 192.168.108.2
然后进行挂载：
mount -t nfs 192.168.108.2:/mnt/nfs /mnt/nfs
如果无法挂载，运行 service rpcbind start或 service portmap start命令试一下。
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