Richard L. Hamilton wrote:
> Well, one exception: I would _not_ recommend swapping to a lofi block
> device, esp not one based on a tmpfs file!
I'm more interested in block devices that are mounted using iSCSI or 
similar.  Didn't swap via
NFS have to use a remote file mounted as a block device?

Even then the situation is not what you seem to be describing with a 
tmpfs file.

I've not used the diskless support - just dataless with local swap and 
cachefs on the workstation
drive.

For this analysis though, I'm trying to determine whether *any* current 
*nix can reliably swap
over a network to any kind of block device using its internal NIC rather 
than an iSCSI HBA
which looks like a disk controller to the device.

It seems to me that emulation of such a device (ie with its own IP stack 
that hooks in at a low
level to IP) would fit the bill - essentially by moving the memory 
reservation and allocation
problem - but no system currently has such a facility.  I'm hoping 
someone will say I'm
wrong in this - and I'm wondering if it might be possible to achieve a 
similar effect using Xen
or xVM or whatever with a swapless dom0 that can provide a swap facility 
to a guest.  But I
don't know whether that would work either.

James


>   That latter case is (a) useless,
> since it's not actually adding any swap, and (b) is just begging for a 
> deadlock
> or worse.  The system may not prevent you from doing it, either; I just
> did (on a Solaris 8 workstation), but didn't push it to the point of _using_
> the swap on the lofi device on top of the tmpfs file, so I got all that torn
> down again without crashing my workstation.
>
> (Actually, as long as one didn't create a sparse file with mkfile -n, I 
> suppose
> it _might_ not lock or crash the system to swap via a lofi device based on
> a tmpfs file, but since it doesn't actually provide more swap space, I'm 
> having
> a hard time imagining any good reason to do it at present.)
>  
>  
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