[Beowulf] Data Destruction

[Ellis Wilson]

Apologies in advance for the top-post -- too many interleaved streams 
here to sanely bottom-post appropriately.

SED drives, which are a reasonably small mark-up for both HDDs and SSDs, 
provide full drive or per-band solutions to "wipe" the drive by revving 
the key associated with the band or drive.  For enterprise HDDs the 
feature is extremely common -- for enterprise SSDs it is hit or miss 
(NVMe tend to have it, SATA infrequently do).  This is your best bet for 
a solution where you're a-ok with wiping the entire system.  Note 
there's non-zero complexity here usually revolving around a non-zero 
price KMIP server, but it's (usually) not terrible.  My old employ 
(Panasas) supports this level of encryption in their most recent release.

Writing zeros over HDDs or SSDs today is an extremely dubious solution. 
  SSDs will just write the zeros elsewhere (or more commonly, not write 
them at all) and HDDs are far more complex than the olden days so you're 
still given no hard guarantees there that writing to LBA X is actually 
writing to LBA X.  Add a PFS and then local FS in front of this and 
forget about it.  You're just wasting bandwidth.

If you have a multi-tenant system and cannot just wipe the whole system 
by revving encryption keys on the drives, you're options are static 
partitioning of the drives into SED bands per tenant and a rather 
complex setup with a KMIP server and parallel parallel file systems to 
support that, or client-side encryption.  Lustre 2.14 provides this via 
fsencrypt for data, which is actually pretty slick.  This is your best 
bet to cryptographically shred the data for individual users.  I have no 
experience with other commercial file systems so cannot comment on who 
does or doesn't support client-side encryption, but whoever does should 
allow you to fairly trivially shred the bits associated with that 
user/project/org by discarding/revving the corresponding keys.  If you 
go the client-side encryption route and shred the keys, snapshots, PFS, 
local FS, RAID, and all of the other factors here play no role and you 
can safely promise the data is mathematically "gone" to the end-user.

Best,

ellis

On 9/29/21 10:52 AM, Paul Edmon via Beowulf wrote:
> I guess the question is for a parallel filesystem how do you make sure 
> you have 0'd out the file with out borking the whole filesystem since 
> you are spread over a RAID set and could be spread over multiple hosts.
> 
> -Paul Edmon-
> 
> On 9/29/2021 10:32 AM, Scott Atchley wrote:
>> For our users that have sensitive data, we keep it encrypted at rest 
>> and in movement.
>>
>> For HDD-based systems, you can perform a secure erase per NIST 
>> standards. For SSD-based systems, the extra writes from the secure 
>> erase will contribute to the wear on the drives and possibly their 
>> eventually wearing out. Most SSDs provide an option to mark blocks as 
>> zero without having to write the zeroes. I do not think that it is 
>> exposed up to the PFS layer (Lustre, GPFS, Ceph, NFS) and is only 
>> available at the ext4 or XFS layer.
>>
>> On Wed, Sep 29, 2021 at 10:15 AM Paul Edmon <pedmon at cfa.harvard.edu 
>> <mailto:pedmon at cfa.harvard.edu>> wrote:
>>
>>     The former.  We are curious how to selectively delete data from a
>>     parallel filesystem.  For example we commonly use Lustre, ceph,
>>     and Isilon in our environment.  That said if other types allow for
>>     easier destruction of selective data we would be interested in
>>     hearing about it.
>>
>>     -Paul Edmon-
>>
>>     On 9/29/2021 10:06 AM, Scott Atchley wrote:
>>>     Are you asking about selectively deleting data from a parallel
>>>     file system (PFS) or destroying drives after removal from the
>>>     system either due to failure or system decommissioning?
>>>
>>>     For the latter, DOE does not allow us to send any non-volatile
>>>     media offsite once it has had user data on it. When we are done
>>>     with drives, we have a very big shredder.
>>>
>>>     On Wed, Sep 29, 2021 at 9:59 AM Paul Edmon via Beowulf
>>>     <beowulf at beowulf.org <mailto:beowulf at beowulf.org>> wrote:
>>>
>>>         Occassionally we get DUA (Data Use Agreement) requests for
>>>         sensitive
>>>         data that require data destruction (e.g. NIST 800-88). We've
>>>         been
>>>         struggling with how to handle this in an era of distributed
>>>         filesystems
>>>         and disks.  We were curious how other people handle requests
>>>         like this?
>>>         What types of filesystems to people generally use for this
>>>         and how do
>>>         people ensure destruction?  Do these types of DUA's preclude
>>>         certain
>>>         storage technologies from consideration or are there creative
>>>         ways to
>>>         comply using more common scalable filesystems?
>>>
>>>         Thanks in advance for the info.
>>>
>>>         -Paul Edmon-
>>>
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> 
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