SAN BASICS..Why we will go for SAN?

1. Why we will go for SAN?
 In DAS HDDs are connected in a single path and
bandwidth also shared.
 SCSI cable length is max. 25 meter and can
connect max. 16 disks
 Maintenance down time is there
 Application needs performance

2. Why we will go for SAN?
 Scalability
 Difficult backup management
 Inaccessible to data during maintenance

3. I/O Channel SCSI
 Few devices connected
 Static (One to one) (can’t attaché another
server)
 Low latency

4. I/O Channel SCSI
 Short distance 25 meter
 Hardware based delivery management (Block
level)

5. I/O channel (Ethernet)
 Many Devices connected
 Dynamic Plug and play
 High latency

6. I/O channel (Ethernet)
 Longer distance
 Software based delivery management
(TCP/IP)

7. I/O Channel (FC)
 Many devices 16 Million
 Dynamic
 Low latency Micro second

8. I/O Channel (FC)
 Long distance 1000KM
 Hardware based delivery management (Block
level)

9. Every Advantage over other protocol
Disadvantage-Costlier Initially ……

10. Introduction
to
Storage Area Network

11. What is Storage Area Network
Storage Area Network (SAN) is a
specialized, high speed, high availability
network that uses fiber channel
technology to connect servers to storage
disks.

12. Common SAN Definitions
 Node -Any device connected to the SAN (servers, Tap drives,
Tape library, VMware server, Unix server etc.…)
 WWN (world wide Name)-Unique identifiers used to identify
storage devices
 Fabric-Encompasses all hardware that connects servers and
workstations to storage devices through the use of fiber
channel switching technology
 Fiber Channel-High speed network technology used mainly
for the storage area

13. Design Considerations
 Should solve an underlying business need.
 Meet business requirements for availability
and reliability
 Be scalable to meet current and future
business needs
 Be cost-effective and easy of manageability

14. Benefits of a SAN
 Eliminates restrictions on the amount of data that can be
accessed by an individual server as oppose to server with
direct attached disk.
 Storage can be accessed by multiple serves simultaneously
with more robust, faster processing.
 Storage resources can be centrally managed and storage
space can be allocated and deallocated to hosts as needed.
 Components are hot-swappable, eliminating downtime

15. Three Basic Forms of Network Storage
 Direct access storage (DAS)
 Network attached storage (NAS)
 Storage area network (SAN)

16. Direct Attached Storage

21. Quick Overview

23. Small Computer System Interface
(SCSI)
 From Shugart’s 1979 SASI implementation
 An I/O bus for peripheral device, such as hard drives, tape drives,
CD-ROM, scanners, etc.
 an improvement over IDE
 A single SCSI bus connects multiple elements (max 7 or 15).
 High speed data transfer:
 Overlapping I/O capability:
 Multiple read & write commands can be outstanding simultaneously
 Different SCSI drives to be processing commands concurrently rather than
serially. The data can then be buffered and transferred over the SCSI bus at
very high speeds

24. SCSI Distribution Architecture
 SCSI is a client/server architecture.
 The client is called the initiator and issues request to the
server. The client is I/O subsystem under the typical OS
control.
 The “server” is called the target, which is the SCSI
controller inside the storage device. It receives, process,
and responds to the requests from the initiator.
 SCSI commands support block I/O, transferring large
amount of data in blocks.

25. SCSI Client/Server Architecture

26. SCSI Block I/O Operation

27. SCSI Transport Mechanism

28. Network Attached Storage (NAS)
 Specialized storage device or group of storage devices providing
centralized fault-tolerant data storage for a network

29. Network Attached Storage (NAS)

30. Network Attached Storage (NAS)
 NAS is a dedicated storage device, and it operates in a
client/server mode.
 NAS is connected to the file server via LAN.
 Protocol: NFS (or CIFS) over an IP Network
 Network File System (NFS) – UNIX/Linux
 Common Internet File System (CIFS) – Windows Remote file system
(drives) mounted on the local system (drives)
 evolved from Microsoft NetBIOS, NetBIOS over TCP/IP (NBT), and Server Message Block
(SMB)
( NETBIOS is an acronym for Network Basic Input/output System. It provides
services related to the session layer of the OSI model allowing applications on
separate computers to communicate over a local area network. As strictly an API,
NetBIOS is not a networking protocol)

31. NAS Device
 NAS devices, which typically do not have a keyboard or
display, are configured and managed with a browser-based
utility program.
 Each NAS resides on the LAN as an independent network
node and has its own IP address.

32. NAS DEVICE BENEFIT
 An important benefit of NAS is its ability to provide multiple clients on the
network with access to the same files.
 Prior to NAS, enterprises typically had hundreds or even thousands of
discrete file servers that had to be separately configured and maintained.
Today, when more storage capacity is required, NAS appliances can simply
be outfitted with larger disks or clustered together to provide both vertical
scalability and horizontal scalability.
 Many NAS vendors partner with cloud storage providers to provide
customers with an extra layer of redundancy for backing up files.

33. NAS USE CASES
 In the home, NASes are often used for storing and serving multimedia files
and for automated backups. Many smart homes rely on NAS to provide
centralized storage for smart TVs, security systems and other Internet of
Things (IoT) components in the home.
 In the enterprise, a NAS array can be used as a backup target for archiving
and disaster recovery.
 If a NAS device has a server mode, it can also function as an email,
multimedia, database or print server for a small business.
 Some higher-end NAS products can hold enough disks to support RAID, a
storage technology that turns multiple hard disks into one logical unit in
order to provide better performance times, high availability and
redundancy.

34. NAS PRODUCT CATEGORIES
 NAS devices are grouped in three broad categories based on
the number of drives,
 Drive support
 Drive capacity
 and scalability

35. High-end or enterprise NAS
 The high end of the market is driven by businesses that need
to store huge amounts of files, including virtual machine (VM)
images. High-end NAS provides rapid access and NAS
clustering capabilities.

36. Midmarket NAS
 This end of the market can accommodate businesses that
require several hundred terabytes of data. But this Midmarket
NAS devices cannot be clustered.

37. Low-end or desktop NAS
 The low end of the market is aimed at small businesses and home users
who require local shared storage. Increasingly, this market is shifting
toward a cloud NAS model.

40. What is Direct Attached Storage
(DAS)?
 Direct Attached Storage (DAS), the name is pretty self-explanatory. A
disk subsystem that is directly connected to a host rather than going
through a switched network, thereby giving the host exclusive access to
the disks. The category obviously includes disks internal to a physical
server, but in the storage realm we most often think about JBOD (“just a
bunch of disks”) shelves attached to a server via SAS cable.
(or)
Direct attached storage (DAS), also called direct attach storage, is digital
storage that is attached directly to a computer or a server. In other words,
DAS isn't part of a storage network. The most familiar example of DAS is
the internal hard drive in a laptop or desktop PC. In practice, the phrase
direct attached storage is used most often in reference to dedicated
storage arrays attached directly to servers.

41. HDD (Hard disk)
 1956: IBM ships the first hard drive in the RAMAC 305 system. The
drive holds 5MB of data at $10,000 a megabyte.
 Rotational speed-Measured in revolutions per minute (RPM), most
disks you'll consider for enterprise storage rotate at speeds of 7,200,
10,000 or 15,000 RPM with the latter two being the most common.
A higher rotational speed is associated with a higher performing
disk
 Average latency-The time it takes for the sector of the disk being
accessed to rotate into position under a read/write head.

43. HDD IOPS calculation
 Average seek time- The time (in ms) it takes for the hard drive's
read/write head to position itself over the track being read or
written. There are both read and write seek times; take the
average of the two values.
 Average IOPS= (1 / (average latency in ms +
average seek time in ms).

44. HDD IOPS calculation
 Rotational speed: 10,000 RPM
 Average latency: 3 ms (0.003 seconds)
 Average seek time: 4.2 (r)/4.7 (w) = 4.45 ms (0.0045 seconds)
 Calculated IOPS for this disk: 1/(0.003 + 0.0045) = about 133
IOPS
 Access time=Seek time + Rotational delay (4 to 10ms)

45. HDD IOPS calculation
 1 sector=512Bytes (Disk block size)
 1.Sequential access and 2. Random access
 If access time is 10ms (One operation)
 Then 1 sec how many operations=1000ms/10ms=100 IOPS
 SAS or FC =200 IOPS
 NL_SAS =100 IOPS
 EFD (Enterprise Flash drive) = 4000 IOPS
 Oracle Block size =8K
 200*8kb=1.6MB per sec (Random access)
 Sequential access will take 30 to 100 MB per sec

46. RAID (Redundant Array of
Independent Disks)
 RAID (redundant array of independent disks;
originally redundant array of inexpensive disks) provides a way
of storing the same data in different places on multiple hard
disks (though not all RAID levels provide redundancy). By
placing data on multiple disks, input/output (I/O) operations
can overlap in a balanced way, improving performance. Since
multiple disks increase the mean time between failures
(MTBF), storing data redundantly also increases fault
tolerance.

47. BLOCK SIZE
 File system block size 4k (OS-Linux,
SOLARIS,WINDOWS)
 Application Block size 8k
 Exchange block size 1K
 VNX BLOCK size 64KB
Windows can support maximum block size 64K due to
SCSI

48. RAID
 A group of hard disks is called a disk array
 RAID combines a disk array into a single virtual device
called RAID drive
 Provide fault tolerance for shared data and applications
 Different implementations: Level 0-5
 Characteristics:
 Storage Capacity
 Speed: Fast Read and/or Fast Write (Performance)
 Resilience in the face of device failure (Fault tolerance)

49. RAID Functions
 Striping
 Write consecutive logical byte/blocks on consecutive physical disks (Parallel)
 Mirroring
 Write the same block on two or more physical disks
 Parity Calculation

50. RAID LEVELS
 RAID 0 – striping (Min-2 and Max-16)
 RAID 1 – mirroring (Min-2 and Max-2)
 RAID 5 – striping with parity(Min-3, max-16)
 RAID 6 – striping with double parity (Min-4,
Max-16)
 RAID 10 – combining mirroring and striping
(Min-2, Max-16

51. RAID level 0 – Striping
 In a RAID 0 system data are split up
in blocks that get written across all
the drives in the array. By using
multiple disks (at least 2) at the same
time, this offers superior I/O
performance

52. RAID level 0 – Striping
Advantages-:
 RAID 0 offers great performance, both in read and write
operations. There is no overhead caused by parity
controls.
 All storage capacity is used, there is no overhead.
 The technology is easy to implement
Disadvantages-:
 RAID 0 is not fault-tolerant. If one drive fails, all data in
the RAID 0 array are lost. It should not be used for
mission-critical systems

53. RAID 0- Ideal Use
 RAID 0 is ideal for non-critical storage of data that have to be read/written
at a high speed, such as on an image retouching or video editing station.

54. RAID level 1 – Mirroring
 Data are stored twice by writing them to both the
data drive (or set of data drives) and a mirror drive
(or set of drives) . If a drive fails, the controller uses
either the data drive or the mirror drive for data
recovery and continues operation. You need at
least 2 drives for a RAID 1 array.

56. RAID-1 Advantages
 RAID 1 offers excellent read speed and a write-speed
that is comparable to that of a single drive.
 In case a drive fails, data do not have to be rebuild,
they just have to be copied to the replacement drive.
 RAID 1 is a very simple technology.

57. RAID-1 Disadvantages
 The main disadvantage is that the effective storage capacity is
only half of the total drive capacity because all data get
written twice (Costly)
 No performance gain

58. RAID-1 Ideal Use
 RAID-1 is ideal for mission critical storage, for
instance for accounting systems. It is also
suitable for small servers in which only two
data drives will be used.

59. RAID level 5
 RAID 5 is the most common secure RAID level. It requires at least 3 drives
but can work with up to 16. Data blocks are striped across the drives and
on one drive a parity checksum of all the block data is written. The parity
data are not written to a fixed drive, they are spread across all drives, as
the drawing below shows. Using the parity data, the computer can
recalculate the data of one of the other data blocks, should those data no
longer be available. That means a RAID 5 array can withstand a single drive
failure without losing data or access to data. Although RAID 5 can be
achieved in software, a hardware controller is recommended. Often extra
cache memory is used on these controllers to improve the write
performance.

63. RAID-5 Advantages
 Read data transactions are very fast while write data
transactions are somewhat slower (due to the parity
that has to be calculated) –High read performance
 If a drive fails, you still have access to all data, even
while the failed drive is being replaced and the
storage controller rebuilds the data on the new drive.
–Fault tolerance

64. RAID-5 Disadvantages
 Drive failures have an effect on throughput, although
this is still acceptable.
 This is complex technology. If one of the disks in an
array using 4TB disks fails and is replaced, restoring
the data (the rebuild time) may take a day or longer,
depending on the load on the array and the speed of
the controller. If another disk goes bad during that
time, data are lost forever.

65. RAID-5 Ideal use
 RAID 5 is a good all-round system that
combines efficient storage with excellent
security and decent performance. It is ideal for
file and application servers that have a limited
number of data drives

66. RAID level 6 – Striping with double
Distributed parity
 RAID 6 is like RAID 5, but the parity data are written to two
drives. That means it requires at least 4 drives and can
withstand 2 drives dying simultaneously. The chances that two
drives break down at exactly the same moment are of course
very small. However, if a drive in a RAID 5 systems dies and is
replaced by a new drive, it takes hours to rebuild the swapped
drive. If another drive dies during that time, you still lose all of
your data. With RAID 6, the RAID array will even survive that
second failure.

68. RAID-6 Advantages
 Like with RAID 5, read data transactions are very fast.
–High read performance
 If two drives fail, you still have access to all data, even
while the failed drives are being replaced. So RAID 6
is more secure than RAID 5. –High fault tolerance

69. RAID-6 Disadvantages
 Write data transactions are slowed down due to
the parity that has to be calculated.
 Drive failures have an effect on throughput,
although this is still acceptable.
 This is complex technology. Rebuilding an array in
which one drive failed can take a long time.

70. RAID-6 Ideal use
 RAID 6 is a good all-round system that
combines efficient storage with excellent
security and decent performance. It is
preferable over RAID 5 in file and application
servers that use many large drives for data
storage

71. RAID level 10 – combining RAID 1 &
RAID 0
 It is possible to combine the advantages (and disadvantages) of RAID 0
and RAID 1 in one single system. This is a nested or hybrid RAID
configuration. It provides security by mirroring all data on secondary drives
while using striping across each set of drives to speed up data transfers.
 For more random access we can go for this raid and EMC called this raid as
fastest raid.
 Mirroring + Striping (Gives highest performance as there is no calculation
happening)

74. RAID-10 Advantages & Disadvantages
 If something goes wrong with one of the disks in a RAID 10 configuration,
the rebuild time is very fast since all that is needed is copying all the data
from the surviving mirror to a new drive. This can take as little as 30
minutes for drives of 1 TB. (high read and write performance and fault tolerance)
&
 Half of the storage capacity goes to mirroring, so compared to large RAID
5 or RAID 6 arrays, this is an expensive way to have redundancy.