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Storage Concepts for IT Pro 2-Controllers and Models

06/16/2013

In the first article of this series http://msincic.wordpress.com/2013/05/13/storage-concepts-for-it-pros-raid-types-and-iops/ we discuss some important and basic concepts for it professionals about the RAID types available and used today in arrays and also how to calculate IOPS (reading and writing operations) for each type of disk and applications.

In this article we will cover the most common types of controllers and models of arrays.

The following table taken from Microsoft’s document "Characterizing and Analyzing IO Size Considerations" available in http://bit.ly/18nlbTg shows how the physical controller bus type used for your storage influences directly on performance:

image

HBA – Host Bus Adapter

This is a very bus type used before the iSCSI and very efficient, connecting the storage directly with the server by a dedicated Board, being used by Fibre Channel (example Compellent) or direct-attached model (example MD3000).

As can be seen in the table above, for being a dedicated bus have all the performance without competition, different from the iSCSI HBA in each server connects to a storage or output to a dedicated switch and iSCSI use two network trips to all servers.

In addition, a dedicated storage are at least two, redundant controllers and seat for access, ensuring safety and high performance.

The downside of HBA models is due to the limitation of possible connections, since in some models (example MD3000) are 4 doors, limited to 4 servers. For this model using HBA and assemble a cluster of 4 us is a good alternative.

Fibre Channel

The FC is one of HBA models widely used due to the high performance and unlimited number of hosts that can be connected by Fibre Channel switch.

In addition, FC allows boot of Diskless servers, which guarantees the replacement of a host just putting another identical hardware and changing the WWN in storage.

In FCs storages use the World Wide Name (WWN) to indicate which LUNs will be used for each server, it is very simple to be held and configured. With Windows 2012 we can deliver arrays directly VMs for creating a virtual WWN in Hyper-v:

image

The disadvantage of FC is given by the cost higher than the other solutions involving and iSCSI HBA. However, the technical, administrative and performance advantages make FC the best type of connection to storage.

iSCSI

ISCSI (Internet SCSI) is the most widely used model today on account of the cost accessible, several options of manufacturers, models and sizes. Basically iSCSI uses ethernet network communications, but with some advantages that improve performance if followed:

  • Using separate network switches only for network storage
  • Working with 2 NICs in each server to configure the MPIO (Multipath i/o) that allows you to use the two data access simultaneous, doubling the speed of access
  • Configure Jumbo Frame to work with 9 k data packets rather than 1.5 K, since storage always travels data in larger packages Unlike common communication network

The disadvantage of iSCSI is given exactly by the points above, since the network structure needs to be dedicated to have better performance and redundancy.

ISCSI support can be at storage or even by software that enables a common server to become a storage iSCSI, what is called a Server iSCSI Initiator and the iSCSI client Initiator. Microsoft has this software available, but it is very well known on the market the StarWind iSCSI Initiator Server.

SMB NAS 3.0

The technology of NAS (Network Attached Server) is based on the Windows Server 2012 with SMB 3.0 makes it compatible with virtualization, enabling Hyper-V use a File Server to store virtual machines, allowing them to be mounted a Cluster based only on File Server.

The advantages of this model are low cost, ease of administration and delivery for new servers.

The disadvantages are given on behalf of the network that has the same requirements listed of iSCSI, having some additional considerations:

  • MPIO need to have redundant network cards on the server MESSAGE BLOCK (SMB)-based Direct and non-RDMA trivial templates on servers currently
  • The Jumbo Frame makes that machine users (customers) use the server for file guard, unless you enable the Jumbo Frame them with implications in all Core network switches
  • Arrays are multi-controllers sources, which is not always present on File Servers

Conclusion

Using the types of storages are available and considering your needs it is possible to have a trusted environment and with good performance and redundancy.

Source: http://bit.ly/13uRbOs (Windows Server 2012 White Paper Storage)

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