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ManagingTheDomU

This is an operational document. It details steps to move a DomU from one machine to another in the event of system failure.

In this document, I'm attempting to move a 50Gb VM with a 2Gb RAM allocation. I will do a series of system checks before I do the move. In this document I present those and what actions have to be taken to fix any issues I discover along the way.

1. Find your new host

2. Check it has enough disk space

  ~# vgdisplay
    --- Volume group ---
    VG Name               node0185vg0
    System ID
    Format                lvm2
    Metadata Areas        1
    Metadata Sequence No  192
    VG Access             read/write
    VG Status             resizable
    MAX LV                0
    Cur LV                48
    Open LV               24
    Max PV                0
    Cur PV                1
    Act PV                1
    VG Size               922.00 GiB
    PE Size               4.00 MiB
    Total PE              236033
    Alloc PE / Size       109851 / 429.11 GiB
    Free  PE / Size       126182 / 492.90 GiB
    VG UUID               qkscTI-GoRF-xauD-w87w-lvQl-7C1H-ceTeCM

As you can see, the vldisplay command has shown that we have 492Gb free on this system.

3. Check you have enough free ram

    ~# xm list
   Name                                        ID   Mem VCPUs      State   Time(s)
   Domain-0                                     0   501     8     r----- 903717.7
   xen03                                        1  2048     1     -b----  11742.1
   xen05                                        2   512     1     -b----   5016.2
   xen08                                       15    96     1     -b----   3864.4
   xen13                                       16   512     1     -b----  13691.0
   xen16                                       14    96     1     -b----  32135.6
   xen17                                        7   784     1     -b----   7414.3
   xen18                                        8  2048     1     -b---- 346771.8
   xen19                                        9  1228     1     -b----  38826.1
   xen22                                       10   512     1     -b----  30983.0
   xen29                                       11   512     1     -b----  12942.8

As you can see, we have 8849 mb in use on this system

Check how much ram we actually have in the system...

   # dmidecode > thishardware.txt
   # nano thishardware.txt

   Handle 0x0028, DMI type 16, 15 bytes
   Physical Memory Array
        Location: System Board Or Motherboard
        Use: System Memory
        Error Correction Type: Multi-bit ECC
        Maximum Capacity: 192 GB
        Error Information Handle: Not Provided
        Number Of Devices: 6

   Handle 0x0029, DMI type 19, 15 bytes
   Memory Array Mapped Address
        Starting Address: 0x00000000000
        Ending Address: 0x000000003FF
        Range Size: 1 kB
        Physical Array Handle: 0x0028
        Partition Width: 0

   Handle 0x002A, DMI type 17, 28 bytes
   Memory Device
        Array Handle: 0x0028
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
        Size: 2048 MB
        Form Factor: DIMM
        Set: None
        Locator: DIMM0
        Bank Locator: BANK0
        Type: Other
        Type Detail: Other
        Speed: 1333 MHz (0.8 ns)
        Manufacturer: Manufacturer00
        Serial Number: 00000000
        Asset Tag: AssetTagNum0
        Part Number:

I found we have 6 * 2Gb, which is 12GB, so we have enough free for me to add our 2Gb customer.

4. Check the raid array is ok (this should be the case, but as we're not on every system all the time, we just do a quick check).

   ~# cat /proc/mdstat
   Personalities : [raid1] [raid10]
   md1 : active raid10 sda5[4](F) sdd1[3] sdc1[2] sdb5[1]
      966791424 blocks 64K chunks 2 near-copies [4/3] [_UUU]

   md0 : active raid1 sda1[2](F) sdb1[1]
      979840 blocks [2/1] [_U]

   unused devices: <none>

Ok that's not good! So that will need fixing first as the sda seems to have vanished. Now in this case I happen to know that the sda just came up as sdc on my system, so all I need to do is reassemble the array.

Skip over to our managing RAID page for more help on that if needed.

Page last modified on October 23, 2015, at 01:40 AM EST