Couple iSCSI SAN Questions

[CoreyWilson]

Hey guys,

Couple real quick questions with respect to moving forward with an iSCSI SAN solution.

First off, I realize each server connecting to the SAN requires two network cards, one for the primary network and one for the SAN network. Do the NIC's connecting to the SAN have to be of specific model or brand or will any 1GB card work?

Secondly, this comes down more to the hardware itself and may be to specific from one vendor to another and I am specifically referencing EMC's aix150 here, but does the brand of hard drive matter so long as it meets the requirements, do you have to purchase additional drive directly from the SAN vendor, I realize for IBM or HP which has a larger market and more inventory, but does ECM supply the hard drives? I am guessing simply a seagate or? in order to get the drive cages to install them in the rack.

Thirdly from a scalability standpoint, how effective is an iSCSI SAN solution utilizing SATA drives? We will not be hosting any intensive apps, if any apps at all for that matter. It will be primarily a means of consolidating data in a single architecture and exchange data. With that being said, are there any real shortcomings aside from performance? I realize that iscsi is limited to 1GBps vs 2-4 for that of fibre but a FB SAN is more then most mid-size companies can afford to invest in.

Thanks for your time.

 

[comtec17]

Any 1GB NIC will work, you only need to install and load the iSCSI initiator software. It is also best practice to place 2 NIC's in a machine for iSCSI path failover. This will ensure that your server has redundant connections.

I have answered your second question in the EMC forum.

For your third question, SATA is slow, tier 3 storage. It is not lightning fast. One thing you have to keep in mind is that a 100GB spindle is rotating at the same speed as the new 500GB spindles. This will slow down performance of reads/writes and bursty I/O. The rated throughput of an SATA drive is 50 I/O per second. SCSI and FC rate almost 3 times that and spin 2800 RPM's faster which allow faster seeks.

iSCSI is an affordable solution for Data Centers that have smaller wallets than others. I have personally seen customers purchase a 2GB solution but have some old servers that cannot push that kind of bandwidth out the bus of the server. There are a few areas you really need to know about your environment before you invest into a FC SAN or iSCSI SAN. Some of these areas will include;

Can your server handle faster I/O?

Performance of your current servers

Network Bandwidth currently used

 

[xmsre]

1. You need to make sure that your chosen SAN supports the specific version of the iSCSI initiator you plan to use. For clarification, we are talking about the MS iSCSI software initiator.

2. If your chosen SAN supports jumbo frames, you want to turn that on on both the initator and target. Jumbo frames support a payload of up to 9000 bytes. For 4K IOs, this means an IO will fit in a single frame.

3. Exchange can be very IO intensive and uses small block sizes. SATA is not your best bet. The IOPS/spindle for SATA is far lower than FC, and to get acceptable performance you'll end up using many more spindles.

 

[comtec17]

xmsre, your #2 point is wrong. For clarity, the network itself must support Jumbo Frames from end-to-end. That means the initiator, switches, routers, backbone, and target. An FC frame is 2148 bytes even if you have 2 bytes of data.

A typical network MTU size is 1500 bytes so if you had to move a 2148 byte frame the Server and NIC would need to split this frame in half. By using a Jumbo Frame setting of 9000, it does not give you a frame of 9000 bytes, it allows the channel to pass that large of a frame through if it were that size. There is no queueing when it comes to iSCSI payload, it sends a 2148 byte frame no matter what.