DragonFly commits List (threaded) for 2008-07
Re: cvs commit: src/sbin/hammer cmd_mirror.c cmd_pseudofs.c hammer.8 hammer.c hammer.h
Matthew Dillon wrote:
: HAMMER Utilities: Streaming mirroring!
: * Add a new streaming mirroring feature called 'mirror-stream' which works
Please note that this is not quite ready for testing yet. There is
a race between normal filesystem writes and the mirror's B-Tree scan
which can cause a DATA CRC and other assertions.
In fact, the only known bugs in the filesystem at the moment, assuming
I fixed that blocking bug reported on the lists, is due to buffer
cache aliasing between vnode-mapped buffers and device-mapped buffers.
I think the cluster_read I do on the device-mapped buffers is causing
I hope to have the bug fixed by tomorrow evening.
The new bandwidth-limited streaming mirroring feature is going to be
very spiffy! It's working except for the above bug!
It will make it possible to have a streaming mirror continuously
running in the background but not eating much in the way of system
resources. So instead of batching your backups you would be able to
maintain a continuously running backup. It should also work well for
sporatically connected boxes, like a laptop, where you want it to
maintain a backup automatically whenever it happens to have internet
connectivity, but also not eat up too much of your WIFI bandwidth.
That's pretty cool! One question though: If I'd like to have the exact
same snapshots on each machine, is that as easy as just "copying" the
softlinks? That is, are the transaction ids (those @@0x... numbers :)
identical on the master and it's mirrors?