This is the investigation document which touches each aspect of Low Cost SAN making right from hardware, OS and Softwares. The layered architecture of our SAN is shown in following diagrams.
In this diagram, three boxes in red color depicts the solution for windows and DFS is Microsoft distributed file system for windows server.
4.2 SAN Features and available options
Having above architecture in mind we have tried to achieve all the features of low cost SAN in terms of speed, reliability, security, scalability and availability. Following table gives us an overview against the features and corresponding available options. All the softwares which we have used to achieve SAN features are available on FOSS:
Available Options On FOSS
Low Cost & Simplicity
AoE Protocol and corresponding softwares are available on FOSS.
No routability provides inherent security
Speed of ATA disk
1) Typical 7200-rpm SATA disk drive: 105 MB/s (sustained throughput)
2) Typical 7200-rpm PATA disk drive: 72 MB/s (sustained throughput)
Speed of Ethernet
1) Gigabit Ethernet (1000baseT): 125 MB/s
2)10-Gigabit Ethernet: 1,250 MB/s
AoE simply delivers 48 bytes and data ( only extra 48 bytes )
Full Virtualization Support
Fully Compatible with hypervisors such as Xen, VMware, Microsoft Virtual PC to virtualize computers that are used as servers
We can combine multiple 22 TB disk into a single RAID disk.
Device access through Internet
Remote access to an AoE device through the Internet can be achieved
through tunneling, we can use software to convert local packets into routable packets at both ends of a link.
Easy management of AoE Servers and nodes
AoE Tools like CEC provides a terminal interface for AoE device. All the clusters and nodes can also be managed by RHCS cluster manager
Connecting Multiple Disks
24 port SATA controller PCI express card having capacity >=2TB per disk
Theoretical limits of AoE devices
AoE has a limitation of 65535 major x 255 minor addresses, so you're limited to approximately 16 million block devices on a single broadcast domain / san. For each individual block device, the ATA lba48 addressing restricts you to about 140 PetaBytes.
Diskless booting Support
Diskless booting (PXE booting) is available in AoE for windows as well as for Linux
RHCS fencing daemon provide fencing against corresponding failover domains
Network Load balancing
RHCS lvs and piranha provides network load balancing
Proper Synchronization among all the nodes
RHCS GFS/GFS2 uses DLM to provide this feature
Block Level Redundancy
DRBD is a tool available on Foss to provide high availability in SAN in terms of block level. If DRBD is used with heartbeat and rhcs, it's a very good solution for HA in storage networking.
Directory level Redundancy
NFS fail over and auto mounting is easily handled by RHCS.
Resource Management and ensured communication among other nodes
CMAN of RHCS and Heartbeat are good solutions against this.
4.3 Overview of SAN with HA/Failover
The main challenge of a reliable SAN is high availability and zero down time. Thanks to the tools like LVS, RHCS, HEARTBEAT and DRBD by which we can easily restart our applications and can do migration of services. Following diagram shows the failover a node and relocation of services, so that users get their applications running even if corresponding node crashed.