EMC Storage Product Knowledge Sharing

The Clariion Formats the disks in Blocks. Each Block written out to the disk is 520 bytes in size. Of the 520 bytes, 512 bytes is used to store the actual DATA written to the block. The remaining 8 bytes per block is used by the Clariion to store System Information, such as a Timestamp, Parity Information, Checksum Data.

Element Size – The Element Size of a disk is determined when a LUN is bound to the RAID Group. In previous versions of Navisphere, a user could configure the Element Size from 4 blocks per disk 256 blocks per disk. Now, the default Element Size in Navisphere is 128. This

means that the Clariion will write 128 blocks of data to one physical disk in the RAID Group before moving to the next disk in the RAID Group and write another 128 blocks to that disk, so on and so on.

Chunk Size – The Chunk Size is the amount of Data the Clariion writes to a physical disk at a time. The Chunk Size is calculated by multiplying the Element Size by the amount of Data per block written by the Clariion.

128 blocks x 512 bytes of Data per block = 65,536 bytes of Data per Disk. That is equal to 64 KB. So, the Chunk Size, the amount of Data the Clariion writes to a single disk, before writing to the next disk in the RAID Group is 64 KB.

In order to use the control functions of Solutions Enabler, you must create device groups and add/associate Symmetrix devices with the group. The following example shows how to create a device group, add a standard device to it and associate two BCV devices to the group.
The following commands will create a device group using the default type (regular). Next we will add a device to the device group and assign it a logical name. Then we associate two BCV devices with the device group so we can switch back and forth with the BCV devices.

NOTE: At this point you have only added/associated devices with a device group. These actions do not in any way describe which devices should actually be paired. This may be confusing as the documentation is not very explicit. The fact is that the symmetrix may already have BCV pair information about these devices depending on how they were used in the past.
Now issue the commands to define the STD/BCV pair and actually synchronize the pair with a full establish.

This explicit definition of the STD device and the particular BCV device will cause any existing pair information to be disregarded and will use this new information to create a pair. This is

comparable to the older TimeFinder Command Line Interface "bcv -f filename" where the file "filename" consisted on one line entries pairing STD devices with BCV devices. And finally, split this TimeFinder pair and synchronize the STD device with a different BCV device.