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Tue, 04 Dec 2007

DST FAQ.

The most frequently asked question about DST is:

Can you give us a summary of how this differs from using device mapper with NBD or iSCSI?

From the higher point of view it does not, but it operates quite differently: it has async processing of the requests, thus not blocking, it has different protocol with smaller overhead, supports strong checksums, has in-kernel export server, which supports simple security attributes (i.e. allow to connect, to read or write). It uses smaller amount of memory (zero additional allocations in the common path for linear mapping, not including network allocations, it uses smaller amount of additional allocations for mirroring case). DST supports failure recovery in case of dropped connection (core will reconnect to the remote node when it is ready), thus it is possible to turn off and on remote nodes without special administration steps. DST has simple autoconfiguration at the startup time (support checksums and storage size autonegotiation). It is possible to turn one of the mirror nodes off and use it as a offline backup, since dst mirror node stores data at the end of the storage, so it can be mounted locally.

/devel/dst :: Link / Comments (0)

New distributed storage subsystem release.

This is a maintenance release and includes bug fixes and simple feature extensions only.

Short changelog:

• fixed bug with XFS metadata update (it can provide slab pages to the DST, so it is not allowed to transfer them using ->sendpage())
• fixed async error completion path
• extended netlink communication channel to report errors back to userspace
• DST name is now "The 10'th dynasty of smuggled slothes"
• number of fixes for userspace DST target

/devel/dst :: Link / Comments (2)

The 22'th century netchannels release.

This is the 22'th release of the netchannels, a peer-to-peer protocol agnostic communication channel between hardware and users. It uses unified cache to store channels, allows to allocate buffers for data from userspace mapped area or from other preallocated set of pages (like VFS cache). All protocol processing happens in process context.

Users of the system can be for example userspace - it allows to receive and send traffic from the wire without any kernel interference, to implement own protocols and offload its processing to the hardware.

This idea was originally proposed and implemented by Van Jacobson. This patchset (with userspace netowrk stack) is a logical continuation of the idea with move to the full peer-to-peer processing.

Short changelog:

• update cached route in the netchannel when it expires

/devel/networking :: Link / Comments (0)