On 02/01/15 11:57 AM, Kevin O'Gorman wrote:
On Fri, Jan 2, 2015 at 8:50 AM, Gary Dale <garyd...@torfree.net
<mailto:garyd...@torfree.net>> wrote:
On 31/12/14 04:57 PM, Kevin O'Gorman wrote:
I've just gotten 4 4TB drives to replace my 4 2TB drives. I'm
wanting to have one normal 4TB drive and one logical 12TB
drive, so I will make three physical drives into one group,
one logical volume and one partition support the big
partition. My system actually resides on a fifth: an SSD
drive. I am not interested in RAID, and I'm not sure striping
would even help. I just have gigantic files I need to create
and process once in a while, so it's really temporary space.
I do want to insulate the one drive from any failures on the
other three. That data is not at all temporary, but it is
backed up regularly. I want to limit it's failure profile.
I've read through some documentation, including
http://www.debian-administration.org/article/410/A_simple_introduction_to_working_with_LVM
So I think I know how to do it. I'm just not sure I know how
to do it _best_. I'm a bit daunted by the size of
/etc/lvm/lvm.conf, and wonder if the defaults are going to
work for me.
I'm about to start a backup of the existing system. It will
take a while. I wonder if anyone has wisdom they'd like to share.
I've never had any use for LVM. With 4 x 4T drives, why not create
a single 12T RAID 5 array, or use ZFS or BTRFS as others have
suggested.
I've decided on mdadm, as you suggest. I understand RAID, just not
the details of mdadm. Both ZFS and BTRFS are unknowns to me, so I'll
avoid them for now just because I'm lazy. Would either of them span
multiple drives, or would I have to have a RAID anyway?
MDADM RAID is simple, although it may not be easy to set up when you
already have 4 drives in your system. Most MBs only allow for 6 SATA
devices. However you can set up the array with a couple of simple
commands. And it can be moved between machines because it doesn't depend
on the hardware.
Both ZFS and BTRFS allow just about everything that RAID and LVM offer
plus more. BTRFS is the touted as being the next standard Linux file
system. If I understand it correctly, you can upgrade ext* to btrfs in
place, add new drives into the file system and remove the old ones
(using the correct file system commands).
Of course, nothing is 100% safe but is there a point in telling you to
backup 8T of data first? MDADM RAID would allow you to copy the data to
the new array before removing it from the old disks. Btrfs would allow
you to revert if moving data off a drive runs into a problem. However if
your current data doesn't have redundancy, a failure during the move
could still mean data loss.
This isn't the place for either a RAID or file system tutorial, but
there are lots out there on the web. Search engines will find them for you.
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