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What are the Components need for DAS Setup?
* Host or Sever with PCI or PCI-X or PCI-E slots.
* RAID Controller(one or more) gets connected to any of PCI slots depending on the card support.
* Connectors & Cables depending on the type of interfaces SATA, SCSI, SAS, FC or IDE.
* Firmware for the Controller.
* Operating systems (Windows or Linux or Solaries flavours)
* Driver for the Controller depending on the OS.
* RAID Controller Management software as per the vendor.
* Storage subsystems, Indivisual Drives or Enclosure/Drive tray with drives.
What is FIRMWARE?
Firmware is a combination of software and hardware. Computer chips that have data or programs recorded on them are firmware. These chips commonly include the following:
* ROMs (read-only memory)
* PROMs (programmable read-only memory)
* EPROMs (erasable programmable read-only memory)
How do we upgrade or downgrade Firmware?
Firmwares for controller cards will be available in the respective vendor websites.
Firmware upgrade/Downgrade can be done using specific Utilities or third party tools as specified by the vendor.
Outline the Configurations supported by RAID controller cards in DAS?
* Logical drive creation/deletion/modification:
Using one or more drives connected to RAID controller card, can create Logical drives according to the RAID level (RAID0,1,3,5,6,10,50 etc.) choosen.
LD configuration created can be removed at any point of time by deletion options. the LD properties such as Stripe size, cache size, rebuild rate, Initialization rate etc can be modified for the specific LD configurations.
Modification to Logical drive properties depends on the Vendor support.
* Syncronization or Initialization:
Usually when new LD is created, Syncronization starts automatically, it is much like formating process but syncronization erases the previous data & add 0's to all the sectors of the Logical drives.
Initialization can be done manually on the existing LD, whenever you like to erase the old data on the LD, initialization can be started.
Fast initialization options erases only the Mettadata information of the LD, not entire LD data & hence it is fast initialization.
Full initialization options erases all data present on the entire LD & hence it is slow process takes hours depending on the LD configuration & Implementation.
* Rebuild Logical Drive:
Rebuild of Logical drive starts due to redundancy feature of RAID, whenever any drive fails within redundant Logical drives, upon insertion of new drive Rebuilding of data takes place & it takes hours to rebuild data depending on the RAID level & properties of specific LDs.
* RAID Level Migration:
Some cards support RAID level Migration but not all the raid levels can be changed to each other, for example RAID1 (2 drives) can be migrated to RAID5 (3 drives) but RAID0 (2drives) cannot be migrated to RAID1(2drives), limitation is total storage capacity which is more in RAID0(2drive) than RAID1(2drives).
Also, it depends on the Vendor implimentations (see picture).
* Reconstruction:
Logical Drive data reconstruction happens for 2 reasons;
>> when Logical drive capacity is expanded (increased), for example: Old Raid config RAID1 with say 20 GB was configured &80 GB remained unused, can be increased upto the free capacity available in the specific raid config(80GB in this example).
>> When RAID Level Migration is started.
* HotSpare:
Some RAID cards allow user to assign unused drive as Hotspare. after configuration Hotspare will remain in standby mode, if any drive fails in Redundent array hotspare will automatically act as replacement drive for failed drive.
main use of the Hotspare is elimination of manual action of removing failed drive & inserting new drive to specific RAID config.
Vendors provide Local Hotspare (assigned to specific Raid config, work for only the Raid config to which it is assigned) & Global Hotspare (can get assigned to any of raid config within storage subsystem, acts on first come first serve basis).
For expert consultation contact Mail ID: storagetrendz@gmail.com
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