On 11/13/20 2:34 PM, Bill Bogstad wrote:
An external USB drive that I use solely for full and incremental
backups is developing bad blocks. For pricing reasons, I'm going with
a new drive which uses SMR for recording.
I might be doing that and don't know it. Are the new portable 5TB WD
USB-C affordable disks disk-managed SMR? If so, I am. (Before that, a
sequence of old "super speed" USB disks and somewhat smaller capacity,
depending on purchase date.)
I wondered why, after I am done with the backup, I can feel the disk
vibrating, still doing something for some time later. I do note the
USB-Cs are shorter in this than were the previous models. Maybe that was
the disk managing itself.
I backup with rsync and a
hard link tree for incrementals which means that file data is
typically not overwritten at the file level. Metadata of old files
changes when a hard link in a new incremental is made to the
preexisting file. A
That I *am* doing and have been doing for sometime. (rsync and
--link-dest is great!) And because these disks are affordable I
ping-pong between multiple disks, kept in different locations.
Because I litter these in various locations, I encrypt them; luksFormat
the whole disk, and then format with XFS.
Donno why I chose XFS, seemed like a good idea back when.
This has worked well, I have not only done backups but also done
"restores" (for copying my data to a new computer, more than once, only
a couple times grabbing a specific old file).
The whole system has worked great, I really like that every time I do a
backup I am smoke testing that the disk still significantly works and
will ~likely~ be able to do a restore. (I would like a Linux file system
that is error checked, but last I looked I didn't see a good option for
that.)
It is nice that the backup directly mountable, making the "restore time"
extremely short if I can do what I need directly off the disk.
That last couple disks (the USB-C) I have been a good camper and written
the entire disk with high quality random data before luksFormat and mkfs.
re there any things I should watch out for this
use case? Particular filesystems that are either good or bad for SMR
drives? I obviously want the system to be reliable, but I doubt that
making the system rewrite shingles over and over again due to frequent
updates to the same disk blocks is good for the longevity of the
drive. Any info/opinions appreciated.
A disk managed SMR (if done well) is not going to rewrite the shingles
that much, it is going to remap things to avoid that. Isn't it?? But the
remapping isn't free, some usage patterns are going to stress it. I do
my incremental backups every few days at most, and even then I am
rotating that across more than one disk, so each backup is significant
in size, the ratio of meta data rewrite to new data isn't going to be
that high. If disk managed SMR firmware can work with any usage pattern,
I think the write-once nature of this backup scheme should be pretty
friendly.
-kb
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