Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Greg Freemyer <greg.freemyer at ...> writes: > > On 2/15/07, Greg Freemyer <greg.freemyer at ...> wrote: > <snip> > > As to: > > > > "You can stack DRBD on top of md, md on top of DRBD is nonsense, however". > > > > I still don't know why that is true in a active-passive setup. It > > seems totally logical to me to stack md raid0 above drbd raid1 in a > > active-passive setup, but that may be different thread. > > > I was thinking some more about this and I believe the issue is with > ordered writes. > > IIRC, drbd provides 3 modes of operation related to ordered writes. > By stacking a raid layer above drbd you break its ability to control > ordered writes because no single instance of drbd sees the whole > picture. I'm not a drbd expert, but if you look at the 3 modes you > can probably see why it would be bad even in a active passive setting. > > Greg I'm thinking (hoping?), that because each separate DRBD will preserve the correct write ordering of its chunk of the raid-0 stripe; the overall write ordering of the entire stripe will also be preserved. I guess that I'm just going to have to dig into the combinitorial discussion in the DRBD docs; and then, of course there's tons of testing to do. _Rick