Hello everybody, I think some people in here are familiar with the idea of creating temporary filesystems in RAM, that gives a huge performance boost at some workloads (e.g. MySQL). However, those setups never got widely used because of one problem: the whole thing crashes if you run out of space in the ramdisk. One guy (Yves Trudeau) said "Let's use a union filesystem and the problem will be solved! It will write to ramdisk while it has free space, and use the HDD when the ramdisk is full" (www.bigdbahead.com/?p=137). However, that guy never published any code.
I'm now trying to revive that idea. Yves Trudeau proposed using UnionFS-FUSE, but it obviously can't handle anything like that. MHDDFS is much closer to the solution, but it's still FUSE-based. AuFS seems to be a perfect way to fix the ramdisk problem; however, I've failed to find the proper mount options. I need a creation policy that fills the ramdisk first, and after it's filled, writes to the HDD. Looks like I need either "top-down-freespace" that doesn't care about parents and writes to the highest branch that has enough free space, or a "least-free-space" policy with out-of-disk errors suppression. Is this possible to achieve with AuFS? If yes, how to do it? Cheers, -- Sergey "Shnatsel" Davidoff ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1
