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What's good about iSCSI?

Posted on 2011-02-10
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I have very limited knowledge and experience with external storage solutions. All my experience is to setup NAS devices. I do not know SAN or things like that.

Recently we will need to purchase one more Buffalo TeraStation III, I see they have an iSCSI version of TeraStation III, and it is not much more expensive at all. Who would be able to explain to me in plain language regarding the following questions?
1. What is good about iSCSI? Why I should use iSCSI as opposed to a NAS?
2. Does iSCSI have to be "attached" to a server? If so, we have a Dell PE2900, would this server work with iSCSI?

Thanks in advance
jack
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Question by:techcity
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by:SterlingMcClung
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iSCSI differs from NAS protocols like nfs and smb/cifs in the fact that iSCSI shares block devices over the network and nfs/smb/cifs shares files.  To the server, an iSCSI drive looks almost identical to an internal drive.  This means that only a single server can attach to an iSCSI share.  As long as the iSCSI server, TeraStation in your case, is connected to the network, you are OK.  Performance wise it makes sense to have a dedicated network for the iSCSI data, but it will work with everything on one network.  I know that there are iSCSI initators for 2003 and beyond.  Not sure about 2000.  Any linux machine should be able to do this.  Here is a good comparison between iSCSI and NAS:

http://searchstorage.techtarget.com/tip/1,289483,sid5_gci994985,00.html

Just scroll down to see the entire article.
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Thanks. but what is " iSCSI initators"? I saw it in the bios of Dell T610
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1. What is good about iSCSI? Why I should use iSCSI as opposed to a NAS?

iSCSI allows you to externalise the harddrives from your servers.  This is particularly good if you need to build cluster servers where more that one server needs access to the same drive at the same time.  Keep in mind that iSCSI doe not look like a share to servers but rather connects a physical drive to an OS to be mounted as a drive.

In my opinion the biggest differentiator beteen iSCSI and Fiber Chaqnnel is that fiber channel needs specialised (and therefore very expensive) hardware whereas iSCSI uses off the shelf Ethernet cards

2. Does iSCSI have to be "attached" to a server? If so, we have a Dell PE2900, would this server work with iSCSI?

Yes, in iSCSI there are two components to the connection.  The device that contains the physical drives is exposed to the network as an iSCSI Target, and the hardware or software that connects a server to this target is called an iSCSI Initiator.  Pretty much any server that has a software iSCSI initiator can connect to an iSCSI target.
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by:kevinhsieh
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The iSCSI initiator is the component that makes the connection from the server to the storage. It is the functional equivalent of a SCSI or SATA card. Often times it is just a piece of software such as the Microsoft iSCSI initiator. It can also be part of the NIC BIOS, or it can be an HBA (host bus adapter) which is dedicated as a storage adapter. Windows 2008 and above the the iSCSI initiator included as part of Windows. The latest version for down load for Windows 2000/2003/XP is 2.08.
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=12cb3c1a-15d6-4585-b385-befd1319f825

You generally would use the software iSCSI initiator that is for your operating system, not the initiator that you configure from the BIOS. That is usually used for booting a server from your iSCSI storage.

You do have to attach your server to the iSCSI storage to have access to it as a drive. You can attach multiple servers to the TerraStation, but you can generally only attach 1 server to each LUN (volume). The TerraStation should be able to support multiple LUNs.
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by:wynandkunkel
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Thanks. but what is " iSCSI initators"? I saw it in the bios of Dell T610

iSCSI initiators can be implemented either in hardware or software.  I cannot specifically say for the Del model in question but it would then seem that the server would be able to connect to the iSCSI target even before the OS loads.  In the way the OS would not even know about iSCSI.  As far as the OS will be concerned, there will be harddrives it can use, and it would be oblivious of the fact of whether the drives are directly attached or iSCSI attached.
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Thank you all!!
I got a much better picture of iSCSI now.
Jack
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