[SOLVED] Optimizing disk layout after changing to advanced sector drive?

cosmos

Renowned Member
Apr 1, 2013
134
5
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Hello all,

got a rather old community-version PVE system running:
Code:
# pveversion -v
proxmox-ve-2.6.32: 3.4-172 (running kernel: 2.6.32-44-pve)
pve-manager: 3.4-13 (running version: 3.4-13/4c745357)
pve-kernel-2.6.32-44-pve: 2.6.32-172
pve-kernel-2.6.32-41-pve: 2.6.32-164
pve-kernel-2.6.32-37-pve: 2.6.32-150
pve-kernel-2.6.32-42-pve: 2.6.32-165
pve-kernel-2.6.32-26-pve: 2.6.32-114
pve-kernel-2.6.32-43-pve: 2.6.32-166
lvm2: 2.02.98-pve4
clvm: 2.02.98-pve4
corosync-pve: 1.4.7-1
openais-pve: 1.1.4-3
libqb0: 0.11.1-2
redhat-cluster-pve: 3.2.0-2
resource-agents-pve: 3.9.2-4
fence-agents-pve: 4.0.10-3
pve-cluster: 3.0-19
qemu-server: 3.4-7
pve-firmware: 1.1-5
libpve-common-perl: 3.0-24
libpve-access-control: 3.0-16
libpve-storage-perl: 3.0-34
pve-libspice-server1: 0.12.4-3
vncterm: 1.1-8
vzctl: 4.0-1pve6
vzprocps: 2.0.11-2
vzquota: 3.1-2
pve-qemu-kvm: 2.2-23
ksm-control-daemon: 1.1-1
glusterfs-client: 3.5.2-1

On this system I'm utilising 3 disks:
* /dev/sda is the boot
* /dev/sdb holds the actual VMs
* /dev/sdc holds backups

/dev/sdb used to be a WD blue drive with a native 512 sector size. For performance reasons I replaced this with a WD Black drive, after using dd_rescue to clone the blue to the black.

System boots and works just fine. However, I'm afraid of the disk performance I am losing due to having partitions on the new /dev/sdb misaligned:
Code:
# fdisk -lu /dev/sdb

Disk /dev/sdb: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x7e996182

  Device Boot  Start  End  Blocks  Id  System
/dev/sdb1  63  976768064  488384001  7  HPFS/NTFS/exFAT
Partition 1 does not start on physical sector boundary.
Also:
Code:
cat /etc/fstab
# <file system> <mount point> <type> <options> <dump> <pass>
/dev/pve/root / ext3 errors=remount-ro 0 1
/dev/pve/data /var/lib/vz ext3 defaults 0 1
UUID=e1746fa2-eb42-4aa9-a09d-53cd3c6387b2 /boot ext3 defaults 0 1
/dev/pve/swap none swap sw 0 0
proc /proc proc defaults 0 0
/dev/sdc1 /mnt/backups ext3 errors=remount-ro 0 2

This WD disk holds a VG named ExternalStorage on /dev/sdb1:
Code:
# pvdisplay
  --- Physical volume ---
  PV Name  /dev/sdb1
  VG Name  ExternalStorage
  PV Size  465.76 GiB / not usable 1.50 MiB
  Allocatable  yes
  PE Size  4.00 MiB
  Total PE  119234
  Free PE  88770
  Allocated PE  30464
  PV UUID  9EPIVy-go2e-3k2W-L2Y7-5g3Z-NQFj-Bp0XmC

  --- Physical volume ---
  PV Name  /dev/sda2
  VG Name  pve
  PV Size  297.59 GiB / not usable 4.00 MiB
  Allocatable  yes
  PE Size  4.00 MiB
  Total PE  76182
  Free PE  4094
  Allocated PE  72088
  PV UUID  BKx0SX-Ycta-hi1f-24zL-VMb6-O4F6-tubCC0

ExternalStorage VG details:
Code:
# vgdisplay ExternalStorage
  --- Volume group ---
  VG Name  ExternalStorage
  System ID
  Format  lvm2
  Metadata Areas  1
  Metadata Sequence No  28
  VG Access  read/write
  VG Status  resizable
  MAX LV  0
  Cur LV  3
  Open LV  2
  Max PV  0
  Cur PV  1
  Act PV  1
  VG Size  465.76 GiB
  PE Size  4.00 MiB
  Total PE  119234
  Alloc PE / Size  30464 / 119.00 GiB
  Free  PE / Size  88770 / 346.76 GiB
  VG UUID  VPXGW3-DzKg-J6iF-t1jR-fCkr-TbF7-ZUZEAI

Contained in ExternalStorage:
Code:
  --- Logical volume ---
  LV Path  /dev/ExternalStorage/vm-103-disk-3
  LV Name  vm-103-disk-3
  VG Name  ExternalStorage
  LV UUID  pv6pdD-fPCJ-1Rbt-3FGu-k7Sk-jIgr-zXeetc
  LV Write Access  read/write
  LV Creation host, time pve-1, 2015-11-04 13:08:05 +0200
  LV Status  available
  # open  0
  LV Size  24.00 GiB
  Current LE  6144
  Segments  1
  Allocation  inherit
  Read ahead sectors  auto
  - currently set to  256
  Block device  253:1

  --- Logical volume ---
  LV Path  /dev/ExternalStorage/vm-104-disk-1
  LV Name  vm-104-disk-1
  VG Name  ExternalStorage
  LV UUID  bxLeyW-Pb5W-vhOe-hqHs-VdrI-bDgu-7FpXyA
  LV Write Access  read/write
  LV Creation host, time pve-1, 2016-01-04 08:34:59 +0200
  LV Status  available
  # open  1
  LV Size  35.00 GiB
  Current LE  8960
  Segments  1
  Allocation  inherit
  Read ahead sectors  auto
  - currently set to  256
  Block device  253:2

  --- Logical volume ---
  LV Path  /dev/ExternalStorage/vm-100-disk-1
  LV Name  vm-100-disk-1
  VG Name  ExternalStorage
  LV UUID  SlaihD-PDLF-bPgb-0044-cE5A-r1iH-cjncsL
  LV Write Access  read/write
  LV Creation host, time pve-1, 2016-01-05 08:47:25 +0200
  LV Status  available
  # open  1
  LV Size  60.00 GiB
  Current LE  15360
  Segments  1
  Allocation  inherit
  Read ahead sectors  auto
  - currently set to  256
  Block device  253:3

All in all, I'm trying to figure out how to align all things ExternalStorage-related... Being newbie in this area certainly does not help.

Any ideas on how to proceed, has someone tackled this successfully.
 
Replying to myself, I took the logical way of backing up the VMs stored in the WD disk to another disk, removed the VMs, removed the VG, PV and /dev/sdb1 and recreated the latter one. This time it was 4k-aligned. Recreated the PV, VG, configured the Vm storage from web admin and restored the backups. Nicely done with proxmox :)
 
Following up from this... My physical drives are aligned and happy. But, I get notes like this for VM disks. How do I fix that? Do I need to fix that? Is it just a bug in fdisk?

Disk /dev/zd240: 12 GiB, 12884901888 bytes, 25165824 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 8192 bytes
I/O size (minimum/optimal): 8192 bytes / 8192 bytes
Disklabel type: dos
Disk identifier: 0x6fde7e00

Device Boot Start End Sectors Size Id Type
/dev/zd240p1 * 2048 22661119 22659072 10.8G 83 Linux
/dev/zd240p2 22663166 25163775 2500610 1.2G 5 Extended
/dev/zd240p5 22663168 25163775 2500608 1.2G 82 Linux swap / Solaris

Partition 3 does not start on physical sector boundary.

gdisk -l shows:
root@pve2:~# gdisk -l /dev/zd240
GPT fdisk (gdisk) version 0.8.10

Partition table scan:
MBR: MBR only
BSD: not present
APM: not present
GPT: not present


***************************************************************
Found invalid GPT and valid MBR; converting MBR to GPT format
in memory.
***************************************************************

Disk /dev/zd240: 25165824 sectors, 12.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 625685BF-56BC-49F2-B147-0545CC50F87A
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 25165790
Partitions will be aligned on 2048-sector boundaries
Total free space is 6077 sectors (3.0 MiB)

Number Start (sector) End (sector) Size Code Name
1 2048 22661119 10.8 GiB 8300 Linux filesystem
5 22663168 25163775 1.2 GiB 8200 Linux swap
 
Last edited:
Can't really tell, not a Linux expert here. However, the first/data partition seems to be just fine, so perhaps you could delete the swap and the extended partition and do directly a swap partition. Check if the issue persists.