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We are considering adding a SAN.

I have two choices right now, the Dell MD3000 and the Dell MD3000i, 15 x 146Gb san drives.

Naturally the latest model is more expensive (2x as much), but can someone tell me if the speed difference is considerable to be worth the extra cost?

Our DB on Sql Server 2008 r2 is only about 30Gb and not expected to grow much over the next few years. We have 2 db and 2 web severs that will share this new san.

What metric should I be looking at to verify if the non-iscsi model will work fine for us?

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As far as I know, the MD3000 isn't SAN capable. It's a DAS (Direct Attached Storage) device. –  joeqwerty Jan 3 '13 at 23:29

2 Answers 2

up vote 2 down vote accepted

Sequential read and write performance is the metric you should care about.

SAS == 300 MB/s
iSCSI == less :)

The MD3000 is SAS-attached and intended for two servers (assuming multipath) or four servers. Those are oversubscribed 3Gbps SAS links. The typical use-case is a database cluster of two nodes, but this can also be used as low-cost virtualization storage or just general selective-presentation direct-attached disk space.

The MD3000i is iSCSI attached. More flexibility for more hosts, but not capable of the same sequential read/write performance as the higher-bandwidth 3Gbps SAS link.

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so you are saying the older model is faster? I think with 2 db servers, we should be fine then. –  Alex Jan 4 '13 at 15:30
    
Just saying that it can be faster under specific circumstances. Are you sure about the relationship between the two products? They were marketed by Dell at the same time. Different applications... –  ewwhite Jan 4 '13 at 16:18

One would argue that the md3000 isn't a true SAN, but simply shared DAS. In some cases, DAS can be faster than iSCSI depending on connectivity options, but is more limited in the number of hosts it can support (even more so when trying to have redundant paths to the storage) compared to iSCSi connectivity. the MD3000 will likely require an external SAS HBA to be purchased as well, the 3000i may require additional NIC's and/or switching gear depending on your current infrastructure.

All this being said, you haven't really told us what your needs on the DB's as well as the web servers connected to it (expected IOPS, read/write ratio, expected RAID settings, etc) along with the current/expected usage of the other servers you are planning on connecting and desired level of redundancy, etc.. From your general description, either would be probably be fine from a performance perspective but with 4 hosts, the MD3000 will only allow a single path to the storage. the 3000i could allow you to setup MPIO with iSCSi (assuming you have the appropriate number of NIC's and switching).

This also borders on a "what do I buy" type of question which is generally frowned upon here.

Is there a reason you are set on only those two options?

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For our current DB and Web server, we are running Raid 10 on dell r510 and r620 servers. We plan to set up Hyper V next week, so we can start using live migration capability (within our cabinet and to a offsite server). Which bring up a related question, Is it not more cost effective to just use Hyper V live migration rather than install a SAN? My focus is two part- HA-DR, speeding up our application would be a bonus in this case. –  Alex Jan 4 '13 at 14:54

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