Re: OT:Question on NVME disk direct access?

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On 04/04/2018 09:43 PM, Michael D. Setzer II wrote:

Thanks for the reply. There are lots of issues with doing cloning.
Usually, doing a disk clone gets arround issues where the boot loader is
using the blkid, since it makes the blikids for the partitions the same. Problem
with that thou is that you can't have to disks in the same machine with the
same blkids. Once cloned a disk, and then rebooted it to the OS without
disconnecting, and for some reason, it mounted some partitions from the first
disk, and others from the second?

Same issue with the boot loaders using the /dev/sdx option. If you clone a
disk on /dev/sda to /dev/sdb it works fine, but if you remove sda to test if it
will boot, it will not since second disk with have sdb instead of the sda. Have
to switch cables, or change boot order in bios.

Contacted the person in charge of the nvme program, and he says it should
work as it does with the virtualbox test I did.

Chuckle.  I have the same problem.  My two backup drives and my clone
drive fit into a removable SATA drive sleeve.  If I forget to remove
the clone drive after I do the clone, Fedora will boot off the clone
drive and mix things up as you describe.  I researched as to why
this happens and it is all do to both drives having the same UUID
numbers on their partitions.

I am not in my office at the moment, but when I do get back, I can
send you a bash script I wrote to warm me when this happens.  Let
me know if you would like it.

I frequently forget to swap out the clone drive and reinsert one
of the backup drives.  The first clue is that it takes about
eight times longer to boot.


User was using a windows program called eraser to clear the drive, but from
what I have just found it seems to be a security eraser, and rights random
data to the unused space as contrasted to writing nulls. Think the program
was probable working just fine, but with completely random data the lzop
compression doesn't work well. About twice the speed of gzip but 10% larger
images. I could take a 1T disk, and compress it down to a 40G file with
Windows 10 and Fedora 25 on it.

If you what to completely blank a disk out, don't mess around with that
operating system whose name I shall not mention.  (I hear it is slow,
buggy, and expensive.)  Stay in Linux.

   # dd bs=1M if=/dev/zero of=/dev/sdx

/dev/zero is the fastest, but you also have /dev/one which is slower
and /dev/random which is really slow.


My classroom setup also, had and NFTS clone image file on a separate
partitions, and had an grub boot option, that would reimage the 160G
Windows 10 partition in about 12 minutes.  About a 20G image file.

Have a program on the g4l disk that will zero out the unused space, so have
asked the user to try using that to clean disk, and then make image.

Hopefully, that will result in the expected compression.

Take a look at Clone Zilla, it does all that for you:
http://clonezilla.org/

The author is extremely responsive to questions too.

I use Clone Zilla with its rescue mode (advanced setting) on
NTFS drives with bad sectors on them ALL THE TIME.

What ?? Yes, I have to work on THAT operating system whose name I
shall not mentions too.  My customer base is mainly small
businesses and they can not get apps to run on anything other
than THAT operating system.  It is what it is.

Tip: stay the hell away from Intel SSD drives.  I use to sell them.
They are garbage.  I took around a $2000 loss so far having to replace
them as they go bad in my customer's machines.

I switched to Samsung SSD's and they are rock solid.  Not a
single failure yet.  They are about 20% more expensive than
Intel's drives, but when your have to replace them for free
and just before they brick and lose your customer's data,
they become extremely expensive.

Samsung's NVMe drives are awesome.  (My wife named them NeVada
Medical Examiner drives to remember the abbreviation.)

Tip: try to size your SSD drives such that they have at least 50%
or more free space on them.  This improves your wear life.  And
the wear leveling algorithm on the drive will adore you.



Thanks again for the info.

You are most welcome.

-T
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