Hi,

And thank you for all contributions.

On Mon 2020-05-11 19.40.15, Greater London Linux User Group wrote:

On Mon, May 11, 2020 at 01:15:55PM +0100, James Courtier-Dutton via GLLUG wrote:
<snip>
If you have a separate data from the OS partition:
you could "rsync -avpP"  the data/image/picture/whatever files over to
the new disks on top of LVM.
You could handle the OS partition offline.
You can then do a final "catch up" rsync of the data in offline mode.
<snip>

Can I add a suggestion to use '-H' ('--hard-links') to the list of
rsync options to make sure that files which are hard links are not
copied as separate non-linked files?

This is important for the OS partitions, where several deb packages
install the same file under different names (eg bzip2).

It does have the downside of being slightly slower as it has to check
for hard links, so might be skipped for those filesystems where you
know there are no hard links.

I feel rather nervous as I am about to do all this, and I do have some 
questions (see below).

1. Create Physical Volumes on the two new 8 TB hard disk drives:

  pvcreate /dev/sdc
  pvcreate /dev/sde

2. Create a Volume Group containing these Physical Volumes

  vgcreate vg_blobs /dev/sdc /dev/sde

3. Create a mirrored Logical Volume using this Volume Group

  lvcreate -n lv_blobs -m1 vg_blobs
Questions:
  - How do I make the new volume use all available space? Will mirroring choose 
the physical volumes automatically?
  - Where does the log go? = Do I need a partition on a separate disk for it? 
How large should it be and how do I incorporate it?

4. Create a new file system on the mirrored LV

  mkfs.ext4 /dev/vg_blobs/lv_blobs

5. Copy the data from the existing RAID-1 system (on sda and sdb) to the new 
mirrored LV

  rsync -at <RAID mount point> <LV mount point> # or -avpP or -avpPH?

6. How do I then remove sda + sdb from RAID-1 md127p1?

7. How do I eliminate RAID-1 md127p1?

8. Create Physical Volumes on the two old 8 TB hard disk drives:

  pvcreate /dev/sda
  pvcreate /dev/sdb

9. Do I now extend the Volume Group created in step 2 or do I create a new 
Volume Group?

  vgextend vg_blobs
Or: vgcreate vg_blobs2

10. ?

  lvextend

  Or:
lvresize

11. Grow the filesystem to 16 TB.

Are there any more ideas concerning these commands and their options?

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