1.精简卷介绍

redhat官网详细介绍：

https://access.redhat.com/documentation/zh-cn/red_hat_enterprise_linux/8/html/configuring_and_managing_logical_volumes/creating-and-managing-thin-provisioned-volumes_configuring-and-managing-logical-volumes

2.精简卷环境测试

2.1.添加测试磁盘（sdb）

[root@csdb ~]# lsblk 
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda             8:0    0   35G  0 disk 
├─sda1          8:1    0  300M  0 part /boot
└─sda2          8:2    0 34.7G  0 part ├─rhel-root 253:0    0 17.7G  0 lvm  /├─rhel-swap 253:1    0    2G  0 lvm  [SWAP]└─rhel-u01  253:2    0   15G  0 lvm  /u01
sdb             8:16   0    1G  0 disk 
sr0            11:0    1  4.2G  0 rom

2.2.创建并挂载精简卷

## 创建pv
[root@csdb ~]# pvcreate /dev/sdbPhysical volume "/dev/sdb" successfully created.## 创建vg
[root@csdb ~]# vgcreate vg_cs /dev/sdbVolume group "vg_cs" successfully created## 创建精简卷池
[root@csdb ~]# lvcreate -L 1010M -T vg_cs/cspoolRounding up size to full physical extent 1012.00 MiBThin pool volume with chunk size 64.00 KiB can address at most 15.81 TiB of data.Logical volume "cspool" created.## 创建精简卷
[root@csdb ~]# lvcreate -V 200G -T vg_cs/cspool -n lv_csWARNING: Sum of all thin volume sizes (200.00 GiB) exceeds the size of thin pool vg_cs/cspool and the size of whole volume group (1020.00 MiB).WARNING: You have not turned on protection against thin pools running out of space.WARNING: Set activation/thin_pool_autoextend_threshold below 100 to trigger automatic extension of thin pools before they get full.Logical volume "lv_cs" created.## 挂载精简卷
[root@csdb ~]# mkfs -t xfs /dev/vg_cs/lv_cs
meta-data=/dev/vg_cs/lv_cs       isize=512    agcount=16, agsize=3276800 blks=                       sectsz=512   attr=2, projid32bit=1=                       crc=1        finobt=0, sparse=0
data     =                       bsize=4096   blocks=52428800, imaxpct=25=                       sunit=16     swidth=16 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=25600, version=2=                       sectsz=512   sunit=16 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0[root@csdb /]# mkdir cs
[root@csdb ~]# mount /dev/vg_cs/lv_cs /cs
[root@csdb ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root     18G  3.9G   14G  22% /
devtmpfs                 894M     0  894M   0% /dev
tmpfs                    910M     0  910M   0% /dev/shm
tmpfs                    910M   27M  884M   3% /run
tmpfs                    910M     0  910M   0% /sys/fs/cgroup
/dev/sda1                297M  161M  137M  54% /boot
/dev/mapper/rhel-u01      15G  6.0G  9.1G  40% /u01
tmpfs                    182M   12K  182M   1% /run/user/42
tmpfs                    182M     0  182M   0% /run/user/0
/dev/mapper/vg_cs-lv_cs  200G   33M  200G   1% /cs

2.3.数据库测试

## 创建测试表空间
SQL> create tablespace cs datafile '/cs/cs01.dbf' size 600M;Tablespace created.[oracle@csdb ~]$ df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root     18G  3.9G   14G  22% /
devtmpfs                 894M     0  894M   0% /dev
tmpfs                    910M     0  910M   0% /dev/shm
tmpfs                    910M   27M  884M   3% /run
tmpfs                    910M     0  910M   0% /sys/fs/cgroup
/dev/sda1                297M  161M  137M  54% /boot
/dev/mapper/rhel-u01      15G  6.1G  9.0G  41% /u01
tmpfs                    182M   12K  182M   1% /run/user/42
tmpfs                    182M     0  182M   0% /run/user/0
/dev/mapper/vg_cs-lv_cs  200G  633M  200G   1% /cs此时空间使用率查看正常，添加600M数据文件，使用空间也相对增加，剩余空间还有很多很多，继续添加数据文件测试。SQL> alter tablespace cs add datafile '/cs/cs02.dbf' size 600M;
alter tablespace cs add datafile '/cs/cs02.dbf' size 600M
*
ERROR at line 1:
ORA-01119: error in creating database file '/cs/cs02.dbf'
ORA-27052: unable to flush file data
Linux-x86_64 Error: 5: Input/output error
Additional information: 1此时，出现错误ORA-01119、ORA-27052。## 查看错误介绍
[oracle@csdb ~]$ oerr ORA 27052
27052, 00000, "unable to flush file data"
// *Cause:  fsync system call returned error, additional information indicates which function encountered the error
// *Action: check errno[oracle@csdb ~]$ oerr ORA 01119
01119, 00000, "error in creating database file '%s'"
// *Cause:  Usually due to not having enough space on the device.
// *Action:有明显的原因，就是因为由于设备上没有足够的空间导致的。此时，df -h看到的空间使用率才1%，基本上未使用。这就涉及到了一个精简卷的问题，从上面测试中可以看到，实际总磁盘大小1GB，分配1GB给精简卷池，从精简池中又分配200GB空间给精简卷，远远大于磁盘、VG、精简池的大小，从而导致了df -h数据的不准确。
如果没有上帝视角，不清楚精简卷，只看df -h的显示结果，也可能会脑袋一懵。建议使用 lsblk 或 lvs -a -o +devices 查看实际所用磁盘大小或lvm的大小。