ISCSI storage solution Recommendation ?

Question

Hi I am trying to understand where exactly does iSCSI fit in the storage solutions.
is iSCSI recommended ?
My interest:
I would like to provide our users, access to our mass storage, provided by, Sun Fire V890 via 6130 Storage Arrays.
Our users working from their windows box would like to have their mass storage directories mounted as their network drive. Does iSCSI software initiative or hardware HBA's fit into these requirements ???
Can anyone please provide any form of guidance to develope an understanding of the requirements.
thank you!

Answer 1

Hi,
Depending on your situation iSCSI might be a low-cost replacement of a Fibre Channel SAN.
Both are block-level storage solutions. That is, the protocols access devices by reading/writing blocks of raw data not knowing what file they belong to.
The advantages of iSCSI are that it communicates over IP and as such is even able to use the internet for connecting servers and storage placed in a remote location (FC is able to do that too but requires extra, expensive, routing hardware).
Furthermore, if it is about connecting local storage to a server iSCSI can use a basic UTP cabling based ethernet infrastucture which is a lot cheaper than an FC infrastructure. One should however keep in mind that iSCSI requires a separate network to be able to perform well, so connecting iSCSI devices over a company network that is used for other communications too is not a good idea.
To get good performance an iSCSI ethernet infrastructure should at least be Gigabit based and should be redundant to get availability.
FC SAN's are definetly the ones with the better performance. This is due to the infrastructures which are running at 4Gbit/s (most common in recent setups). iSCSI is mostly implemented based on a 1 Gbit/s infrastructure.
As said, both FC and iSCSI are block-based. If you need the storage to replace a fileserver both are not the right solation. In that case you need a NAS (network attached storage) solution which are able to get you file-sharing capabilities right away (CIF, NFS etc.).
(iSCSI and/or FC can be behind the NAS-device as the actual storage, that would involve so called gateways).
An issue that always comes up using iSCSI is that it is not fully vendor independant. The server to connect have to run a so called iSCSI Initiator and, to avoid problems, only those initiators can be used that are certified by the storage vendor. Furthermore the iSCSI initiator takes quite a lot of CPU power of the server to connect so the server should have a lot of CPU power left to handle it. There is a solution for this: using rather expensive networkcards that have an initiator implemented in hardware (so called iSCSI HBA's, or TOE= TCP Offload Engines, HBA's allow for booting from iSCSI too) but besides of being expensive these initiators need to be on the storage vendor's certified list too.
So iSCSI is not as open as it seems to be in the first place (Things are getting better however).
FC is not free of all these compatibiliy problems. In fact, depending on the storage vendor you chooce, there are several compatibiltyy matrices to be met in order for the total solution to be certified. You should leave the design of a FC SAN to a single specialist who knows were to find and how to use these matrices.
My advise would be to first decide on the budget (based on business requirements), than decide on wether file or block access is needed from the storage device and what OS-platforms are to connect, and decide on the performance you need.
This would lead you to the right choice for storage technology.
Regards,
Willeon