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On 11/9/17 2:01 AM, David Christensen
wrote:
On
11/08/17 17:44, Bob Weber wrote:
On 11/8/17 5:59 PM, David Christensen
wrote:
I have read articles about building a
RAID 1 with three drives, migrating in
data, pulling one drive and placing it off-site, operating in
degraded mode on
two drives, and then periodically re-installing the third
drive, resilvering,
pulling one drive and placing it off-site, and returning to
degraded
operations on two drives. But STFW just now, I see a lot of
posts with titles
indicating this is a bad idea.
...
But what I really want is some form of
snapshot technology (rsync/hard link,
LVM, btrfs, ZFS) with all the goodies -- realtime compression,
realtime
de-duplication, and encryption. I need a more powerful backup
server (many
core processor with AES-NI, 16+ GB RAM, SSD caches, etc.).
I have used raid 1 to make a drive I can
take off site for backup. You just
grow the raid 1 array by one disk and add the disk you want to
take out (even on
a usb/sata connection ... but slow). Of course the disk or
partition(s) need
to be the same size as the array. Let it sync and then boot to
a live cd and
you can fail and remove that drive. Or just power down and
remove the drive.
That way the embedded file system will be unmounted correctly.
I have then
taken that one drive and connected it to another system and been
able to run the
raid 1 in degraded mode and mount the embedded file system(s) to
get to the
files. To make the original raid happy just grow the array
again setting the
number of drives back to what it was originally (you can grow to
a smaller
number). The syncing can be slow since every byte on the drive
needs to be
"synced" instead of just the space the files take up.
Okay. What RAID technology were you using -- LVM, mdadm, btrfs,
ZFS, other?
I use software raid with mdadm. Its pretty forgiving with powering
down and removing a drive (after sync) and growing the array back
down to the original size. I mainly do this on my backup server
running backuppc. The files are compressed and hard linked between
backups if they have not changed. This makes any other type of
offsite backup pretty hard ... rsync just ran out of memory. So
adding a drive to the raid 1 and syncing is easy in comparison.
Having grub make the drive bootable (since the os is also on a raid
1 partition) makes the drive very easy to just install in new
hardware and get going again (assuming the original backup system
was destroyed).
--
...Bob
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