CLARiiON
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Image:EMC Clariion CX500.jpg The CLARiiON is EMC's midrange storage array. The CLARiiON was acquired by EMC from Data General, where it had become a successful business. EMC offers both Fibre Channel and Serial ATA disks for this unit.
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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 Availablity 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 current CLARiiON line (CX300, CX500, CX700) and a low end SATA based CLARiiON array, the AX100 (now updated to AX150).
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)
AX100/150 has 12 SATA drives, and emulation that presents 12 FC drives on a single loop to the CLARiiON SPs.
There are two types of DAE - Fibre Channel, or ATA. As of March 2006 CLARiiON supports 36 GB 15krpm, 72 GB 10k or 15krm, 146 GB 10 or 15krpm, 300 GB 10krpm Fibre Channel drives, and 250 Gb 5400 rpm, or 500 GB 7200 rpm ATA drives.
Software
CLARiiON Microcode is called FLARE, the management software is called Navisphere. Management is self contained - to manage an array browse to it's management IP adress, 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. Various features exist in addition to basic RAID functionality:
LUN Migration - LUNs can be moved between RAID types, and between drives types (FC to ATA for instance), online, while hosts are accessing data. It is a slow process though.
SnapView/Snapshots - Snapshots allow to 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 has to be stopped for a brief period. Once snapshot is taken, application can resume I/O on source LUN and other hosts can access the data on snapshot as a regular LUN. Snapshots use principle of COFW (Copy on first write). Modified data blocks on source LUNs are stored in a reserved area and pointers are maintained for tracking. This copy is made only on first write application. Virtual image is presented with help of these pointers, source LUN and blocks stored in reserved LUNs.
SnapView/Clones - Clones allow to create identical copies of any regular LUN within an array. This copy takes exact amount of space as taken by source LUN.
MirrorView - Synchronous or Asynchronous SAN based replication to other CLARiiONs (not on CX300, or AX series arrays)
SANCopy - Copy data to/from other storage arrays on the SAN (including other vendor storage arrays), can be incremental if the CLARiiON is the source of the copy (not AX arrays).
RM/SE - Windows software sitting above SnapView/SANcopy to simplify/automate replication and recovery of SQL Server and Exchange databases on CLARiiONs
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.