The space available inside a PC is limited. In addition, the average user does not perhaps want to get their hands dirty in order to add a hard drive configuration that runs in and risking the damage. In fact, the solution of the SIN is an alternative that is gaining credibility every day, and despite a relatively high cost.
There are variety of iSCSI servers, many of them are proprietary and some of the companies that market include IBM, Sun, HP, etc. As we see, are big companies, and therefore the price of their solutions is usually quite big too. As we do not want to pay others and we are sure that we understand very well the iSCSI technology (assuming they read the previous post in this blog ) They do not need this kind of support, we will install our SAN or Storage Area in good Area Network.
iSCSI is an extension of SCSI, which is not nothing but a protocol for device communication. SCSI is typically used in devices physically connected to a host or server, such as hard drives, CD or tape devices. In iSCSI, the SCSI commands that manage the device, sent over the network. So that instead of having a SCSI disk physically connected to our team, we connect through the network. But that does not already exist with Samba or NFS. No, these systems work by importing a file system via the network. iSCSI hardware device imports the entire network, so that the client is detected as a SCSI device. All this is done transparently, as if the disc is connected directly to hardware.
The simple answer is to centralize and disk storage server information. For example we could have an iSCSI server with 1 Terabyte (1024 Gigabytes) of storage to centralize all storage devices in our network. On the other hand we could have our servers: mail, ftp, web, samba, all without disks or partitions for data. Data disks be connected via iSCSI over the network and if any of our servers were to fall or to maintain them would have the information on a disc that could be "plugged" by the network. So if we have a secondary server, we only have to connect the iSCSI disk and we will walk in a very short service time.
SCSI disks typically provide excellent transfer rates. But if SCSI is carried over the network then the speed and performance could drop severely decline. Why iSCSI is recommended only for high-speed switched networks such as those that provide Gigabit Ethernet. Although iSCSI can run even on Fast Ethernet is not recommended if you seek performance, since disk access is slow down a lot.
The transfer speed of iSCSI is 1000 MB / Sec, but due to protocol, the low speed up to 800 MB / Sec. If we use cards DUAL CHANNEL, such as those with the QNAP, we get to 1600 MB / Sec taking into account losses by protocol.
ISCSI
The iSCSI protocol is an application layer protocol for transporting SCSI commands over a network. The thing to understand is that it is possible to export a device through a network by presenting it as a SCSI device. Besides the fact that the SCSI protocol is a standard industry massively deployed in production, is going through a conventional IP network reduces the cost of implementation compared to the deployment of storage solutions based on Fibre Channel. Furthermore, data backup can be done at the server level iSCSI, which limits the cost of the backup solution.
However, open source solutions are not numerous and it is difficult to convince an IT manager to switch to a solution of this type based on free software. For my part, I tried to use the OpenFile distribution based on rPath Linux (meta-distribution based on RedHat) and iSCSI Enterprise Target for Part iSCSI, but the product has not yet matured enough to consider professional use.
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