Date post: | 09-Aug-2015 |
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Engineering |
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Storage Management
Kasun Rathnayaka
BSc Eng,AM(SL),RHCE,RHCSA,CCIP,CCNA
Why we need Storage devices?
What is Storage devices ?
How it works?
How it Manage ?
Do You Know ?
Example : Human mind
Computer Storage
Storage Types
● Primary storage
– Internal memory , main memory– Directly access to CPU – RAM– Processor registers
● Hold word (32 or 64 bit)of data ● addressed by mechanisms other than main
memory and can be accessed more quickly– Processor cache(L1/L2/L3)
● intermediate stage between ultra-fast registers and much slower main memory
Storage Types
Example
Working example with Linux OS
Disk Partitioning - Linux
● Linux still uses MS-DOS partition table for disks less than 2TB in size.
● It also has GPT (Guide Partition table) to be used with larger SCSI/SAS disks
● MS-DOS partition table uses MBR (Master Boot Record)
● MBR
– Size of MBR is 512 bytes
– MBR keeps
● Boot Loader– GRUB stage 1 (Linux)– NTLDR (Windows)
● Primary partition table (As a data structure :linked list)
Disk Partitioning - Linux
* AA55 or Magic Numbercrafted at the time of manufacturing
* 0-446 bytes are occupied by the boot loader
* 64 bytes are used by the primary partition table
GPT
GPT allocates 64 bits for logical block addresses and therefore allows a maximum partition size of 2^(64)−1 sectors
Storage Types
● Secondary Storage
– External memory
– Differs from primary storage in that it is not directly accessible by the CPU
– The computer usually uses its input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage
● Tertiary Storage
– involves a robotic mechanism
– Mount in mass storage media
● Off line Storage
– Not control in processing Unit
Oh!
Problems
1.Dynamic resizing is not possible or requires third party tools.
2. Maximum size of a file system is limited by the size of the largest physical disk available.
3. Creating a snapshot (point in time backup) of the file system on-line (at run time) is not possible.
4. Number of partitions are limited by the kernel. For example an SCSI disk can have maximum 15 partitions while an IDE disk can have 63 partitions.
Logical Volume
• Abstraction layer between the physical disks and file systems
• Resize(extend or reduce) easily
• Use discontiguous disk space spanning over multiple disks allowing to create file systems larger than the physical disks available.
• Allow point in time backup of file system called snapshots.
Logical Volume
RAID
Redundant Array of Inexpensive Disks
Basic idea is to connect multiple disks together to provide
large storage capacity
faster access to reading data
redundant data
Many different levels of RAID systems
differing levels of redundancy, error checking, capacity, and cost
RAID 0
• Often called striping
• Break a file into blocks of data
• Stripe the blocks across disks in the syste
• no redundancy or error detection
RAID 1
• A complete file is stored on a single disk
• A second disk contains an exact copy of the file
• Provides complete redundancy of data
• Read performance can be improved
- file data can be read in parallel• Write performance suffers
- must write the data out twice• Most expensive RAID
implementation-requires twice as much storage space
RAID 3
• One big problem with Level-1,2 are the disks needed to detect which disk had an error
• Modern disks can already determine if there is an error
-using ECC codes with each sector
• So just need to include a parity disk
RAID 5,10
Network Storage
Network Storage
● Store and Share data access the Network● Mainly to common types
– SAN• Storage Area Network
• Exports block devices via FC (Fiber Channel) and iSCSI protocols
– NAS• Network-attached storage
• Exports file systems (as folders) via NFS and CIFS protocols
Network-Attached Storage
Mainly use File sharing
Not use for server-centric system( ex:email,file management)
Can user multiple NAS devices
Contain one or more disks, often arranged into logical, redundant storage containers or RAID arrays
The protocol used with NAS is a file based protocol such as NFS, Samba or Microsoft's Common Internet File System (CIFS)
Multiple Operating system on the device such as Celerra on EMC's devices or NetOS on NetApp NAS devices
The performance depends on cached memory (the equivalent of RAM) and network interface overhead
NAS:Advantage
● NAS allows multiple server access through a file-based protocol.
● implement simple and low cost load-balancing and fault-tolerant systems.
● For example:
● Corporate e-mail system with multiple, load-balanced webmail servers
● Load-balanced web servers access the same contents from NAS storage
NAS:Disadvantage
● local network will slow down the resulting access time.
● backup solution is more expensive than the storage solution.
● Not support in advance storage environment.
NAS
✔ Heterogeneous Environment✔ Centralized Storage✔ Low Performance✔ Limited scalability✔ Network Congestion during backups & Restore✔ Ethernet Limitations
Example
NAS :Samba,NFS
Storage Area Network
● Centralizing data storage operation● Primarily used to make storage devices, such as disk
arrays, tape libraries, and optical jukeboxes● Administrating all of the storage resources in high-
growth and mission-critical environments can be daunting and very expensive
● SANs can be based upon several different types of high-speed interfaces
● Fibre Channel● iSCSI interfaces
FC vs iSCSI
FC vs iSCSI
FC SAN iSCSI SAN
Fiber network Ethernet network
High cost Lower than FC
Bandwidth 1,2,4,8,10,1 6Gbps Bandwidth 1,2,4,10Gbps
High performances Low than FC,but good for small company
FC SANs use SCSI and FC drives for their high performance and reliability.
iSCSI SANs commonly use SATA and SAS drives, primarily for their low cost and large capacity
Zoning and VSAN
• partitioning of a Fibre Channel Fabric into smaller subsets to restrict interference
• Add security, and to simplify management
• SAN should only be allowed access to a controlled subset of these devices/ports
• Zoning is different from VSAN, in that each port can be a member of multiple zones, but only one VSAN.
• VSAN (similarly to VLAN) is in fact a separate network.
Zoning types
Soft zoning
implemented in software
uses filtering implemented in fibre channel switches to prevent ports from being seen from outside of their assigned zones.
Connect to any port on the switch
Soft Zoning means that the FC switch will place a host WWN in a zone, without dealing with the port numbers they’re connected to in the FC switchhard zoning
Hard zoning
• implemented in hardware.
• physically blocks access to a zone from any device outside of the zone.
• Usually hard zoning is used when using VLANs. You would associate a port into a zone
Zoning types
SAN
➢ Centralized Storage Management
➢ High Degree of Fault Tolerance
➢ Best and superior performance
➢ Storage Consolidation
➢ Fast and efficient backups and restores
➢ Dynamic Scalability
➢ Expensive solution for small setups