a basic active-passive failover cluster typically consists of a RAID (makes your disks HA) and at least two server nodes. the RAID is either dual-ported SCSI or fibre-attached, such that both nodes (or more in the case of fibre) can 'see' the LUNs on the raid at the same time.
the key is having a volume manager that allows 'importing' or 'deporting' of the volume sitting on the shared LUN. Both systems, although they physically can, should never try and write to the shared LUN at the same time. you need to be able to control this, so you can logically move ownership of the volume back and forth between systems, depending on the state of the cluster.
veritas volume manager does this - if a volume is deported, the other system can mount it, etc. i suspect DiskSuite (which comes with Solaris) would do the same thing, but not sure.
if you can wrapper up something to move the ownership of the volume around, then the rest is trivial (ifconfig-ing up and down the network interfaces - i.e moving the primary system's node name between boxes; and starting/stopping Oracle and the sql*net listeners)
as long as both systems will normally obey the rules of the volume manager, you could roll up a basic failover system from scratch pretty easily. (if node B notices the database on node A is down, it takes ownership of the volume, ups server's IP address on it's net interface, and starts oracle.
another nice thing to have, which isn't there by default on most Suns, is the ability to 'kill' the node that is 'thought' to be down. i.e. if it appears that node A is dead, and it really isn't (maybe just the network card is hosed) - you need to be able to ensure that node B can take over without node A holding on to stuff (like the IP address) - SGI provides a serial controller to do this on most of their systems, but Sun doesn't.
anyway, at the very least you need that - the rest you could probably pick up from the usual linux open-source HA packages (heartbeat stuff, process monitoring, notification, etc.)
the only reason HA stuff isn't more popular on linux is due to lack of a world-class volume manager - if such a thing existed, there'd be a lot more HA stuff for linux floating around i bet.
The Data Management System is the first European hardware to be delivered to ISS. It was developed and manufactured in Europe by an industrial consortium led by Daimler-Chrysler of Bremen, Germany. ESA is supplying the system to the Russian partner in return for two flight-unit docking systems (no exchange of funds) for use with a later ESA element, the Automated Transfer Vehicle.
Two parking spots on the station in exchange for a computer system sounds like a deal to me.
Has anyone done this with Java's 2D API? I have an app that dishes up media via a servlet, and I really need to sort out some kind of watermarking -on the fly- (i.e. as the image is being delivered to the browser, with timestamp, ip address, remote_user, etc.) - since the servlet is lit up and running, it would be ideal to do it there in Java, without the overhead of forking a separate perl or imagemagick or gimp process. Both hidden and visible watermarks would be ideal. Any ideas or pointers to existing code?
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looking at their balance sheets, they've lost approx. $55 million over the last three years.
this is broken out into 'production, content, and product', 'sales and marketing', and 'general administrative'.
my guess is most of the cash went into employees' pockets, and advertising/marketing campaigns.
how much you think the top dogs at salon were making back in the good ole days?
i bet there's a good number of people at salon who've raked in salaries in the $ millions over the last few years there.
a basic active-passive failover cluster typically consists of a RAID (makes your disks HA) and at least two server nodes. the RAID is either dual-ported SCSI or fibre-attached, such that both nodes (or more in the case of fibre) can 'see' the LUNs on the raid at the same time.
the key is having a volume manager that allows 'importing' or 'deporting' of the volume sitting on the shared LUN. Both systems, although they physically can, should never try and write to the shared LUN at the same time. you need to be able to control this, so you can logically move ownership of the volume back and forth between systems, depending on the state of the cluster.
veritas volume manager does this - if a volume is deported, the other system can mount it, etc. i suspect DiskSuite (which comes with Solaris) would do the same thing, but not sure.
if you can wrapper up something to move the ownership of the volume around, then the rest is trivial (ifconfig-ing up and down the network interfaces - i.e moving the primary system's node name between boxes; and starting/stopping Oracle and the sql*net listeners)
as long as both systems will normally obey the rules of the volume manager, you could roll up a basic failover system from scratch pretty easily.
(if node B notices the database on node A is down,
it takes ownership of the volume, ups server's IP address on it's net interface, and starts oracle.
another nice thing to have, which isn't there by default on most Suns, is the ability to 'kill' the node that is 'thought' to be down. i.e. if it appears that node A is dead, and it really isn't (maybe just the network card is hosed) - you need to be able to ensure that node B can take over without node A holding on to stuff (like the IP address) - SGI provides a serial controller to do this on most of their systems, but Sun doesn't.
anyway, at the very least you need that - the rest you could probably pick up from the usual linux open-source HA packages (heartbeat stuff, process monitoring, notification, etc.)
the only reason HA stuff isn't more popular on linux is due to lack of a world-class volume manager - if such a thing existed, there'd be a lot more HA stuff for linux floating around i bet.
mt
From the press kit...
The Data Management System is the first European hardware to be delivered to ISS. It was developed and manufactured in Europe by an industrial consortium led by Daimler-Chrysler of Bremen, Germany. ESA is supplying the system to the Russian partner in return for two flight-unit docking systems (no exchange of funds) for use with a later ESA element, the Automated Transfer Vehicle.
Two parking spots on the station in exchange for a computer system sounds like a deal to me.
Perhaps the same CPU that's in my 300M....
Has anyone done this with Java's 2D API? I have an app that dishes up media via a servlet, and I really need to sort out some kind of watermarking -on the fly- (i.e. as the image is being delivered to the browser, with timestamp, ip address, remote_user, etc.) - since the servlet is lit up and running, it would be ideal to do it there in Java, without the overhead of forking a separate perl or imagemagick or gimp process. Both hidden and visible watermarks would be ideal. Any ideas or pointers to existing code?
tia,
ilmdba