CLARiiON
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The CLARiiON is EMC's line of midrange storage arrays. EMC currently offers wide spectrum of arrays within this family, starting from entry level CLARiiON AX150 (capable of accommodating 12 disks) to powerful CLARiiON CX3 model 80 (capable of accommodating 480 disks). The CLARiiON was acquired by EMC from Data General, where it had become a successful business.
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[edit] History
The CLARiiON disk array's humble beginnings came from Data General's engineering department, which created something known as "HADA", an acronym for "High Availability Disk Array".
Patented in 1994, DG's HADA had some interesting features that are now standard in the data storage and computing industry. Features mentioned in the patent paperwork included hot swappability, guide rails for proper electrical contact, and a method to lock the drives in place once they were secured in the channel.
Because of the HADA's innovation, it quickly became the beginning of the CLARiiON line. The CLARiiON line quickly spanned from 7 slot SCSI disk arrays, to 30 slot SCSI disk arrays.
In 1997, Data General's CLARiiON division took the unusual step of adopting an emerging standard - Fibre Channel. The FC5000 array utilized a Fibre Channel Arbitrated Loop connection that doubled the performance of SCSI arrays at that time.
From there, the CLARiiON disk arrays grew into a fast, expandable midrange storage platform culminating in the FC4700 under Data General. After EMC acquired Data General, significant development of a new range of CLARiiON arrays took place, resulting in the first CX series of CLARiiONs (CX200, CX400 and CX600). Processor and bandwidth upgrades brought us the CLARiiON line (CX300, CX500, CX700) and a low end SATA based CLARiiON array, the AX100 (now updated to AX150). In May 2006, EMC introduced the 3rd generation CX-3 series of arrays, consisting of the CX3-20, CX3-40 and CX3-80. These arrays support 4GB/s Fibre Channel drives on the back end. and have many new hot-swappable parts.
[edit] Hardware
Each CLARiiON has two storage processors (SPs), and each SP has two (CX300, CX500), or four 2 GB fibre channel ports for host connections. It also has 1 (CX300), 2 (CX500), or 4 (CX700) 2 GB back end connections to drive shelves known as DAE's (Drive Array Enclosures).
CX300 can address four shelves of 15 disks (60 in total)
CX500 can address eight shelves of 15 disks (120 in total)
CX700 can address sixteen shelves of 15 disks (240 in total)
Depending on the model, EMC offers support for Fibre Channel, Low-cost Fibre Channel (LCFC) and Serial ATA (SATA) disks. For example, CLARiiON AX100/150 accommodates SATA drives only, and has emulation that presents them as FC disks to the SPs; CX300 can accommodate both Fibre Channel and SATA disks; CX3 models 20/40/80 can accommodate both Fibre Channel and FATA disks.
There are two types of DAE - Fibre Channel, or ATA. As of March 2006 CLARiiON supports 36 GB 15krpm, 72 GB 10k or 15krpm, 146 GB 10 or 15krpm, 300 GB 10krpm Fibre Channel drives, and 250 Gb 5400 rpm, or 500 GB 7200 rpm ATA drives.
[edit] Software
CLARiiON Microcode is called FLARE, the management software is called Navisphere. Management is self contained - to manage an array browse to its management IP address. Navisphere is a large Java applet. Multiple arrays can be managed by grouping them into a CLARiiON domain. AX100/AX150 management use an incompatible, but similar web based GUI called Navisphere Express.
CLARiiON offers following RAID options: No RAID (pure disk), RAID-0 (striping), RAID-1 (mirroring), RAID-1/0 (striping with mirroring), RAID-3 (striping with parity), and RAID-5 (striping with distributed parity). Various features exist in addition to basic RAID functionality:
LUN Migration - LUNs can be moved between RAID types, and between drive types (FC to ATA for instance), online, while hosts are accessing data. This can be a slow process depending on various factors.
SnapView/Snapshots - Snapshots create virtual point-in-time copies of a LUN so that they can be accessed by other hosts. Snapshots are created in an instant and application I/O has to be stopped for a brief period. Once the snapshot is taken, application I/O can resume on the source LUN and other hosts can access the data on snapshot as a regular LUN. Snapshots use the principle of COFW (Copy on first write). The first time a data block is written to after the snapshot is taken, the old data is copied to a reserved area. Pointers into the reserved area are maintained and used to present the snapshot as virtual LUN.
SnapView/Clones - Clones create identical copies of any regular LUN within an array. This copy takes the same amount of space as the source LUN.
MirrorView - Synchronous or Asynchronous SAN based replication to other CLARiiONs (not on CX300, or AX series arrays)
SAN Copy - SAN Copy is a tool to copy data to/from other storage arrays on the SAN (including those of other vendors). Standard copies always fully copy the source LUN to the destination LUN. Application I/O must be stopped during this process. Incremental copies make an initial full copy while each subsequent copy only sends the changes made to the source LUN. Application I/O can continue during these copies. However, incremental copies can only be to other storage arrays, not from.
RM/SE - Windows software sitting above SnapView/SANcopy to simplify/automate replication and recovery of SQL Server and Exchange databases on CLARiiONs
[edit] iSCSI
There are three CLARiiON iSCSI models - CX300i, CX500i, and AX150i - these have 1 Gbit copper ethernet interfaces at the front ends, rather than fibre channel. For high end arrays to export iSCSI LUNs an EMC Celerra gateway or functional equivalent is required.
