1. you cannot use this option for nfs based storage since we zero the
files any way when we delete the disk (the only way to actually delete
it in nfs).
2. configuration on the storage side is the administrator decision...
they can choose not to use this option and use a different method on
storage side.
Dafna
On 02/28/2014 08:11 AM, Sandro Bonazzola wrote:
Il 27/02/2014 22:16, Dafna Ron ha scritto:
wipe = writing zero's on the space allocated to that disk to make sure any data
once written will be deleted permanently.
so it's a security vs speed decision on using this option - since we zeroing
the disk to make sure any information once written will be overwritten,
a delete of a large disk can take a while.
I think this may be not really useful, zeroing files on modern file systems
can't grant any kind of security improvement.
According to shred man page:
CAUTION: Note that shred relies on a very important assumption: that
the file system overwrites data in place. This is the traditional way to
do things, but many modern file system designs do not
satisfy this assumption. The following are examples of file systems on
which shred is not effective, or is not guaranteed to be effective in
all file system modes:
* log-structured or journaled file systems, such as those supplied with
AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)
* file systems that write redundant data and carry on even if some
writes fail, such as RAID-based file systems
* file systems that make snapshots, such as Network Appliance's NFS
server
* file systems that cache in temporary locations, such as NFS version 3
clients
* compressed file systems
In the case of ext3 file systems, the above disclaimer applies (and
shred is thus of limited effectiveness) only in data=journal mode, which
journals file data in addition to just metadata. In both
the data=ordered (default) and data=writeback modes, shred works as
usual. Ext3 journaling modes can be changed by adding the data=something
option to the mount options for a particular file system
in the /etc/fstab file, as documented in the mount man page (man mount).
In addition, file system backups and remote mirrors may contain copies
of the file that cannot be removed, and that will allow a shredded file
to be recovered later.
Dafna
On 02/27/2014 04:14 PM, Richard Davis wrote:
Hi
What is the purpose of the "Wipe on delete" option for a VM disk ?
Why would you not want data wiped on delete if the alternative is to leave LV
metadata and other data languishing on the SD ?
Thanks
Rich
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Dafna Ron
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