Raid 0 -- Data is striped across, If one disks fail then entire data will be lost.
Advantage: Best performance, usable capacity equals 100%
Disadvantage: No data protection
Raid 1: Data is mirrored, Disadvantage is require more disks.
Advantage: Single disk failure will not loose the data.
Raid 3: In case of one disk failure: Data rebuilt using information stored on the remaining disks
In case of failure of more than one disk : All data in an array being lost. Parity is single disks
Raid 2: is failure because in this technology ECC is used
Raid 5: Raid 5 is a strped set with distributed parity. Raid 5 does not use a dedicated parity drive. Instead, parity blocks are evenly distributed across all physical disk drives.
Raid 5: is a very popular, due to its good balance between performance, availability, and usable capacity.
Raid 6: Enhanced Data protection : Double drive failure :
Hardware: Dedicated system and array controller to manage the hardware raid.
Software Raid: Host system take care of Raid configuration. Overhead the performance of CPU memory
Raid 10: combination of Raid 0+1 .
Raid 10 is a way to expand mirroring onto four or more disk drives. usable capacity is only 50% of total storage capacity. Mostly used to write archive logs.etc
Arrays and logical drives:
*An array is simply a set of physical disk drives.
*All logical drives (LUN) inside an array will use the same RAID level.
Interface Options:
Serial attached SCSI : A serail communication protocol designed for transfer of SCSI commands and data to and from devices over point-to-point intercinnections.
Parallel SCSI Devices: connectivity of this device is a daisy chain. If one disk fails the entire connectivity to disks is lost.
SAS : Distance limitations - 8 meters per discreet connections. dedicated controller connectivty to each disks, if one disks fails there is no impact to other disks.
SAS expanders, which will support SAN-like capabilities for SAS, are still in development. Speed limit is 3GB ps.
iSCSI Internet Small computer system interface : A network protocol that enables transmission of SCSI commands and data over an IP-based network usually via an Ethernet interface. iSCSI works on Inititator and targets. Inititator is also Host and the targets is Storage.
software initiator is used by software, Hardware initiator is managed by HBA, data processing coming thru software is managed by HBA card/ software .
**DS 3000 speed is 1GBPS
DS 5000 speed is 10gbps..
FC Basics and Benefits:
FC - Fibre Channel - A serial networking interface that supports the transmssion of upper protocols - including SCSI command sets and data - over fiber optic or copper cables.
Fibre Channel--- is a protcol
Fiber optic--- is a medium / cables.
FC -- Distance 10, 000 meters maximum cabling length. suppots upto 16 million addresses.
- High bandwidth -- low latency and high IOPs
Performance + Scalability ---Then go for FC
Performance + Cost -- SAS technology
DS3200 -- SAS disk system
DS3300 --- iSCSI disk system
DS3500 --- FC disk system
DS3000 -- Base unit is 12 disks , expansion upto 48 disks.
DS3300 -- Base unit is 12 disks, expansion upto 48 disks capacity with 1TB (Total 48TB space)
DS3400 --- Works on FC ports , Can be connected directly upto two hosts with SAN switch.
DS5000 controller will have XOR ASIC --Application specific inter connected.
D5000 Controller technology -- Will have built-in Flash drive per controller, This will help incase of power failure all the data written to cache will be moved to Flash drive this is called destaging. When the powers is back the same data will be given to caches.
DAY -2
Caching:
Where sequential data is used: Video streaming
DACstore : Array can be exported and or imported.
IOPS is heavily dependent on the number of disk drives(spindles) for performance.
Drive-limited configurations can result in similar performance between systems with different maximum capabilities
IOPS performance is critical to transactions-based applications with random small-block I/O
300GB 15k rpm 146GB 15k rpm --- both perform well
Zoneing : Logical grouping of host and storage port.
Zones are created based on WWPN No.
NDMP : Network data management protocol used to take backup .. Developed by Legato
IBM XIV Storage:
total 180TB of RAW space out of 15TB is used for Global Hot Spare , 7.5TB Reserved space for metadata, distibution
Remaining 158TB /2 because of primary and secondary controller.
XIV Storage Capacity
A single XIV rack has 180TB of raw capacity, of which 22 TB are required for space capacity (in case of drives failures) and metadata. The dual write protection system leaves 79TB of available.storage capacity ((180-22)/2 = 79). As all data volumes are spread evenly over all the drives, the array can be filled completely if the performance characteristics of the workload are suitable. There is no requirement to reserve capacity for reorganization.
if two drives fail simultaneously (one in the primary data module, one in the secondary data module) By the nature of Nextra's spread-data-across-all-drives approach, the loss of one drive affects all data in that data module, regardless of whether it holds the primary chunks or the mirrored chunks. If another drive fails, but this time in a data module holding the mirrored chunks and while the first failed drive is still being rebuilt, a lot of data will be lost. "
Synchronous remote: is used if the distance is short
VTL : Is actually emulates/emulation of a physical tape library
Deduplication: Deduplication involves referencing the large quantity of data to the first location and deleting the extra copies of the data,
Deduplication is a process used to eliminate redundant data. During the process, a computer’s hard drive is scanned for large sequences of data across comparison windows. While scanning for duplicate data, sequences of eight kilobytes or more are typically picked out. If the sequence is found elsewhere on the storage system, the duplicated file is referenced rather than stored again.
SAN SVC : Is a storage virtulization engine.
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