Requirement
support 4096 physical devices, 16384 devices with multiple IO paths ( multipath ) (link to list thread)
Iscsi Patches - includes scripts History and Links
Overall test plan
OSDL/IBM testing
IBM provided a system with 256 physical devices, commected via fiber to a switch. The switch was then connected to 4 fiber channel controllers ( QLA2300 ) , which caused the operating system to discover and configure 1024 disk devices. The devices were partitioned into 5 partitions, which allowed > 1024 disk partitions to be mounted and accessed.
Scripts available here were created to count, configure and run some IO operations against the disks. ( See Tools/Tarballs above ). No significant problems were exposed by the testing, the system was not configured for very large io. With all disks divided into the maximum 15 partitions ( one extended partition was not mountable ) 3584 disk partitions were created and mounted.
Noteworthy
SuSE's hwscan program takes a very long time to finish ( 10-15 minutes ) and uses up a bunch of CPU. Kernel complains about depreciated SCSI ioctl in use.
hotplug agent programs ( scsi.agent, etc ) also produce a big load spike at inital boot, but run quite quickly
No resource bottlenecks found other than the above long startup time.
Was able to saturate the fiber with 100-150 spindles of disk, depending on the test.
OSDL iSCSI testing
OSDL is using the linux-isci code to simulate large numbers of disk devices from a remote host. We use the unh-iscsi code to provide the target, and have been porting that code to newer kernels.
4k disk test unh-iscsi patch for newer kernels ( may be obsolete )