为AlmaLinux 9.3服务器现有LVM Vault卷组添加SSD缓存的无数据丢失方案咨询

我的AlmaLinux 9.3服务器目前使用LVM配置：

• 一个卷组（VG）映射到系统SSD，包含root和swap两个逻辑卷（LV），这部分运行正常无需改动。
• 另一个名为Vault的卷组由三块硬盘组成，作为数据存储挂载在/vault下。当服务器上的Docker服务关闭后，这个LV可以被禁用且不会影响基础系统运行。

最近我发现特定场景下top命令里的wa值很高，想通过给现有的Vault LVM配置添加SSD缓存来解决这个问题。不过买好SSD还没安装时，我发现大部分指南都是讲安装时集成缓存的，而且很多资料（包括RHEL文档和一些技术博客）都警告说给现有Vault添加缓存会丢失数据。

我之前已经扩展过Vault两次，但从没加过缓存。现在我没有足够的外部存储来备份所有数据，只备份了关键内容，丢失其他数据会很麻烦。有没有人分享过相关经验或者能提供靠谱的操作文档？

相关命令输出 #

pvdisplay输出：

--- Physical volume ---
PV Name               /dev/sdc2
VG Name               system
PV Size               207.88 GiB / not usable 4.00 MiB
Allocatable           yes (but full)
PE Size               4.00 MiB
Total PE              53217
Free PE               0
Allocated PE          53217
PV UUID               JUC0bk-nF8l-YQmR-GZnn-zzvo-pes3-t6rjud

--- Physical volume ---
PV Name               /dev/sdd1
VG Name               vault
PV Size               <9.10 TiB / not usable 2.98 MiB
Allocatable           yes (but full)
PE Size               4.00 MiB
Total PE              2384383
Free PE               0
Allocated PE          2384383
PV UUID               oSUiba-13Zq-Ug7I-Ggwk-aCs4-HeIy-mL8b55

--- Physical volume ---
PV Name               /dev/sda
VG Name               vault
PV Size               <7.28 TiB / not usable <1.34 MiB
Allocatable           yes (but full)
PE Size               4.00 MiB
Total PE              1907721
Free PE               0
Allocated PE          1907721
PV UUID               W3nnD4-LbDZ-krY8-KVOZ-jnl0-1Khb-C56F6W

--- Physical volume ---
PV Name               /dev/sdb
VG Name               vault
PV Size               <20.01 TiB / not usable 4.00 MiB
Allocatable           yes (but full)
PE Size               4.00 MiB
Total PE              5245439
Free PE               0
Allocated PE          5245439
PV UUID               1YIaLl-DRtM-vMAS-1SKb-6iUg-87Gv-2BgnJ1

vgdisplay输出：

--- Volume group ---
VG Name               system
System ID
Format                lvm2
Metadata Areas        1
Metadata Sequence No  3
VG Access             read/write
VG Status             resizable
MAX LV                0
Cur LV                2
Open LV               2
Max PV                0
Cur PV                1
Act PV                1
VG Size               <207.88 GiB
PE Size               4.00 MiB
Total PE              53217
Alloc PE / Size       53217 / <207.88 GiB
Free  PE / Size       0 / 0
VG UUID               BHmjRL-1pC6-Y5FY-tDBd-ID5P-Vvcl-jvmpzA

--- Volume group ---
VG Name               vault
System ID
Format                lvm2
Metadata Areas        3
Metadata Sequence No  6
VG Access             read/write
VG Status             resizable
MAX LV                0
Cur LV                1
Open LV               1
Max PV                0
Cur PV                3
Act PV                3
VG Size               36.38 TiB
PE Size               4.00 MiB
Total PE              9537543
Alloc PE / Size       9537543 / 36.38 TiB
Free  PE / Size       0 / 0
VG UUID               Bi5H7i-FWY5-kMEN-K7aK-0NST-TKjP-sZnpMY

lvdisplay输出：

--- Logical volume ---
LV Path                /dev/system/root
LV Name                root
VG Name                system
LV UUID                Ju9Hve-q3xe-YYa7-msvG-EelX-wQdh-vrMrcS
LV Write Access        read/write
LV Creation host, time core, 2023-01-03 15:00:41 +0100
LV Status              available
# open                 1
LV Size                <191.88 GiB
Current LE             49121
Segments               1
Allocation             inherit
Read ahead sectors     auto
- currently set to     8192
Block device           253:0

--- Logical volume ---
LV Path                /dev/system/swap
LV Name                swap
VG Name                system
LV UUID                SVDs7q-QjNu-LN1W-4Bjm-psC3-kXbH-l6SdZa
LV Write Access        read/write
LV Creation host, time xxx, 2023-01-03 15:00:41 +0100
LV Status              available
# open                 2
LV Size                16.00 GiB
Current LE             4096
Segments               1
Allocation             inherit
Read ahead sectors     auto
- currently set to     8192
Block device           253:1

--- Logical volume ---
LV Path                /dev/vault/vault
LV Name                vault
VG Name                vault
LV UUID                Gxzis5-NCCX-FhQa-e2rv-FNcn-nQpt-7Ni0fV
LV Write Access        read/write
LV Creation host, time xxx, 2019-06-04 22:07:37 +0200
LV Status              available
# open                 1
LV Size                36.38 TiB
Current LE             9537543
Segments               3
Allocation             inherit
Read ahead sectors     auto
- currently set to     8192
Block device           253:2

备注：内容来源于stack exchange，提问作者Rage