Lori Alt wrote:
> Darren J Moffat wrote:
>> As part of the ARC inception review for ZFS crypto we were asked to 
>> follow up on PSARC/2006/370 which indicates that swap & dump will be 
>> done using a means other than a ZVOL.
>>
>> Currently I have the ZFS crypto project allowing for ephemeral keys to 
>> support using a ZVOL as a swap device.
>>
>> Since it seems that we won't be swapping on ZVOLS I need to find out 
>> more how we will be providing swap and dump space in a root pool.
>>   
> The current plan is to provide what we're calling (for lack of a
> better term.  I'm open to suggestions.) a "pseudo-zvol".  It's
> preallocated space within the pool, logically concatenated by
> a driver to appear like a disk or a slice.  It's meant to be a low
> overhead way to emulate a slice within a pool.  So no COW or
> related zfs features are provided, except for the ability to change
> its size without having to re-partition a disk.  A pseudo-zvol
> will support both swap and dump.
> 
> It will also be possible to use a slice for swapping, just as is
> done now with ufs roots.  But we're hoping that the overhead of
> a pseudo-zvol will be low enough that administrators will
> take advantage of it to simplify installation (it allows a user
> to dedicate an entire disk to a root pool, without having to
> carve out part of it for swapping.)
> 
> Eventually, swapping on true zvols might be supported (the
> problems with swapping to zvols are considered bugs), but
> fixing those bugs are a bigger task than we want to take on
> for the zfs-boot project.  We decided on pseudo-zvols as
> a lower-risk approach for the time being.
> 
>> I suspect that the best answer to encrypted swap is that we do it 
>> independently of which filesystem/device is being used as the swap 
>> device - ie do it inside the VM system.
>> '
>>   
> Treat a pseudo-zvol like you would a slice. 


So these new zvol-like things don't support snapshots, etc, right?
I take it they work by allowing overwriting of the data, correct?

Are these a zslice?

<aside>
For those of us who've been swapping to zvols for some time, can
you describe the failure modes?
</aside>

- Bart

-- 
Bart Smaalders                  Solaris Kernel Performance
[EMAIL PROTECTED]               http://blogs.sun.com/barts
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