Deciphering the Proper LVM

Hey guys,

My experience with logical volume managers (lvms) is limited. I’ve often added drives and extended them at work using cloud VMs, but beyond that I’ve never had to resize, remove or really “manage” them (just delete VM when I’m done with it )

I have a home server running CentOS 6. I set up an LVM when I first built it but as a less-informed Linuxer at the time and just want to see what you guys think of the setup and if it should be changed. I’m looking into it more now as I just bought a 4 TB HDD I want to add.


Current Disks:

/dev/sda – 64 GB SSD – assigned to lv_root (supposedly for /, but also has boot sector)

/dev/sdb – 2 TB HDD – assigned to lv_home (supposedly for /home)

Adding a 4 TB HDD to extend /home dirs.


My VG/PV/LV and df -h output is below:

vgdisplay:

Code:
--- Volume group --- VG Name vg_charlie System ID Format lvm2 Metadata Areas 2 Metadata Sequence No 7 VG Access read/write VG Status resizable MAX LV 0 Cur LV 3 Open LV 3 Max PV 0 Cur PV 2 Act PV 2 VG Size 1.88 TiB PE Size 4.00 MiB Total PE 492070 Alloc PE / Size 491923 / 1.88 TiB Free PE / Size 147 / 588.00 MiB VG UUID 89FdWQ-xFkj-oTLQ-r93N-SR5N-oCk1-a04klF

pvdisplay:

Code:
[root@charlie: /dev/vg_charlie]# pvdisplay --- Physical volume --- PV Name /dev/sda2 VG Name vg_charlie PV Size 59.14 GiB / not usable 4.00 MiB Allocatable yes (but full) PE Size 4.00 MiB Total PE 15138 Free PE 0 Allocated PE 15138 PV UUID XvQPeA-IZCU-Bz4o-Ok1d-JtZn-vjYr-mIDGy6 --- Physical volume --- PV Name /dev/sdb VG Name vg_charlie PV Size 1.82 TiB / not usable 1.09 MiB Allocatable yes PE Size 4.00 MiB Total PE 476932 Free PE 147 Allocated PE 476785 PV UUID bxJTA5-h0Me-ahUK-EP7H-Hxvk-U0YG-Yc8lDI

lvdisplay:

Code:
[root@charlie: /dev/vg_charlie]# lvdisplay --- Logical volume --- LV Path /dev/vg_charlie/lv_root LV Name lv_root VG Name vg_charlie LV UUID GizFrC-I1Lw-3hjF-iUMd-bvWc-Ez09-0DYyn6 LV Write Access read/write LV Creation host, time charlie, 2014-07-29 17:56:22 -0400 LV Status available # open 1 LV Size 48.45 GiB Current LE 12402 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0 --- Logical volume --- LV Path /dev/vg_charlie/lv_home LV Name lv_home VG Name vg_charlie LV UUID 4dJHsn-dDLn-ya4q-0IFC-1nRK-s2yi-ulUUpc LV Write Access read/write LV Creation host, time charlie, 2014-07-29 17:56:43 -0400 LV Status available # open 1 LV Size 1.82 TiB Current LE 477995 Segments 2 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:2 --- Logical volume --- LV Path /dev/vg_charlie/lv_swap LV Name lv_swap VG Name vg_charlie LV UUID njaAy6-ef9w-t9pi-dFxF-tNH8-Ja4b-Qyhi2e LV Write Access read/write LV Creation host, time charlie, 2014-07-29 17:56:46 -0400 LV Status available # open 1 LV Size 5.96 GiB Current LE 1526 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:1

df -h:

Code:
[root@charlie: /dev/vg_charlie]# df -hFilesystem Size Used Avail Use% Mounted on/dev/mapper/vg_charlie-lv_root 48G 5.1G 41G 12% /tmpfs 3.8G 164K 3.8G 1% /dev/shm/dev/sda1 477M 169M 283M 38% /boot/dev/mapper/vg_charlie-lv_home 1.8T 1.5T 262G 86% /home

I wanted to check a few things:

1. I’ve heard its not a good idea to set up an LVM for disks at different r/w speeds. Is it a better idea not to have SSD and HDDs on the same LVM?

2. Ideally I want root (/) on the SSD and /home on the HDDs. According to df -h that looks like it is correct, but can I trust df -h with an LVM? Since I wouldn’t think they are directly ‘mounted’.

3. I also noticed there is a swap logical volume but can’t really tell what disk it was created with. Is there a command to check?

4. I’m thinking of upgrading the OS to Centos 7 since 6 is quickly reaching EOL, maybe even doing a fresh install so I can use disk encryption. Is there a good way or resource anyone has on the best way to “break up” an LVM? I’d be worried of file corruption on files that extend to multiple physical disks but maybe this isn’t a problem since each disk is part of its own logical volume?


Sorry in advance for the barrage of info and questions :). Really also just looking for general advice on if and how others have set up LVMs, particularly with different disk types.

Thanks!

Mike

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