![Evgeniy Polyakov](/assets/img/avatar_default.png)
On Mon, Jan 19, 2009 at 10:12:24AM -0800, Randy Dunlap (randy.dunlap@oracle.com) wrote: > > DST build fails when CONFIG_BLOCK=n: DST should depend on block and block device, in the original patch its kconfig entry was in the BLK_DEV menu, so this dependency was satisfied automatically. Should attached patch be pushed into drivers/staging? Reported-by: Randy Dunlap <randy.dunlap@oracle.com> Acked-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
68 lines
3.4 KiB
Text
68 lines
3.4 KiB
Text
config DST
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tristate "Distributed storage"
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depends on NET && CRYPTO && SYSFS && BLK_DEV
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select CONNECTOR
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---help---
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DST is a network block device storage, which can be used to organize
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exported storage on the remote nodes into the local block device.
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DST works on top of any network media and protocol; it is just a matter
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of configuration utility to understand the correct addresses. The most
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common example is TCP over IP, which allows to pass through firewalls and
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create remote backup storage in a different datacenter. DST requires
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single port to be enabled on the exporting node and outgoing connections
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on the local node.
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DST works with in-kernel client and server, which improves performance by
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eliminating unneded data copies and by not depending on the version
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of the external IO components. It requires userspace configuration utility
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though.
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DST uses transaction model, when each store has to be explicitly acked
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from the remote node to be considered as successfully written. There
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may be lots of in-flight transactions. When remote host does not ack
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the transaction it will be resent predefined number of times with specified
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timeouts between them. All those parameters are configurable. Transactions
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are marked as failed after all resends complete unsuccessfully; having
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long enough resend timeout and/or large number of resends allows not to
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return error to the higher (FS usually) layer in case of short network
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problems or remote node outages. In case of network RAID setup this means
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that storage will not degrade until transactions are marked as failed, and
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thus will not force checksum recalculation and data rebuild. In case of
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connection failure DST will try to reconnect to the remote node automatically.
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DST sends ping commands at idle time to detect if remote node is alive.
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Because of transactional model it is possible to use zero-copy sending
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without worry of data corruption (which in turn could be detected by the
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strong checksums though).
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DST may fully encrypt the data channel in case of untrusted channel and implement
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strong checksum of the transferred data. It is possible to configure algorithms
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and crypto keys; they should match on both sides of the network channel.
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Crypto processing does not introduce noticeble performance overhead, since DST
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uses configurable pool of threads to perform crypto processing.
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DST utilizes memory pool model of all its transaction allocations (it is the
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only additional allocation on the client) and server allocations (bio pools,
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while pages are allocated from the slab).
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At startup DST performs a simple negotiation with the export node to determine
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access permissions and size of the exported storage. It can be extended if
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new parameters should be autonegotiated.
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DST carries block IO flags in the protocol, which allows to transparently implement
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barriers and sync/flush operations. Those flags are used in the export node where
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IO against the local storage is performed, which means that sync write will be sync
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on the remote node too, which in turn improves data integrity and improved resistance
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to errors and data corruption during power outages or storage damages.
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Homepage: http://www.ioremap.net/projects/dst
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Userspace configuration utility and the latest releases: http://www.ioremap.net/archive/dst/
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config DST_DEBUG
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bool "DST debug"
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depends on DST
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---help---
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This option will enable HEAVY debugging of the DST.
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Turn it on ONLY if you have to debug some really obscure problem.
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