Mirror disk from two storage

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Hi,

What is a good solution to mirror disks from two different storage arrays? Is it secure to use lvm mirroring on production servers?

Thanks

Sylwester

Responses

Hi Sylwester,

The LVM mirror functionality is available and supported in RHEL, but it's also deprecated. To quote the RHEL 8.2 release notes:

LVM mirror is deprecated

The LVM mirror segment type is now deprecated. Support for mirror will be removed in a future major release of RHEL.

Red Hat recommends that you use LVM RAID 1 devices with a segment type of raid1 instead of mirror. The raid1 segment type is the default RAID configuration type and replaces mirror as the recommended solution.

To convert mirror devices to raid1, see Converting a mirrored LVM device to a RAID1 device.

LVM mirror has several known issues. For details, see known issues in file systems and storage.

I'm going to forward your question to the LVM developers in case they want to add anything.

You can definitely use LVM to "mirror" two storage arrays. Add the two storage arrays to a Volume Group (VG):

$> vgcreate my_vg /dev/ /dev/

Then you can create a Logical Volume (LV) from that VG that you will use:

$> lvcreate -m 1 --name my_lv -l 100%FREE my_vg

  • This will default to creating the newer "raid1" segment type, not the older "mirror" segment type.
  • This command assumes only 2 devices in your VG
  • Note that '-m 1' means "1 additional copy" i.e. a two-way mirror

There are many options you can use with 'lvcreate' - you can also specify a size and which devices you want the RAID array use.

$> lvcreate -m 1 --name my_lv -L 750G my_vg /dev/ /dev/

For more information on creating RAID Logical Volumes with LVM, see the 'lvmraid(7)' man page.