On 13.04.2017 17:43, Alan Altmark wrote:
One of the tenets of a secure system is the idea that you do not leave
residual data on a device that has been removed from a server. It should
be formatted immediately after de-provisioning, prior to placing in the
'available' pool. The primary purpose is to ensure that confidential or
other sensitive data is deleted since it is no longer under effective
access control. The side effect is that you don't have to worry about
driver fingerprints, smudged or partial.
You also cleanse a device when it is first added to the pool since you
don't know where it's been or what it's been doing.
This is one of the reasons people like thin provisioning: you effectively
format the device by simply releasing all of the extents. (Writing zeroes
is SO twentieth century.) Of course, getting people to separate "format"
from "erase" is a tall order. When all you have is a hammer....
Alan,
I fully agree, well put.
In this system, all guests get their disks from a static pool of EDEVICEs.
In the birth of the system, all those SAN disks were empty.
As z/VM does not have any means to provide thin provisioning for minidisks,
I've tried to follow the
above norm by using the 20th century methods
DIRM PURGE CLEAN for de-provisioning guests
DIRM DMDISK CLEAN for de-provisioning single mdisks
I think that meets the security aspects of the policy.
The technical issue I am now wondering is that are the freed blocks formatted
by DIRM CLEANing
process in a way that sles12.2 drivers don't recognize new minidisks on those
blocks as fba devices.
If that's the case, I really have to bring my cleaning processes up to the
century at hand :)
But note: that is not a fact yet! I cannot be sure that just the blocks that
happened to form the
minidisk I was using in this case were formatted by DIRM CLEAN. I'll have to do
more tests..
(Our DIRM CLEAN is still in its factory default settings..)
--
Regards,
Juha
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