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I'm curious about Lefthand SAN solutions from HP. People from Dell have told me that Lefthand SAN's require at least two nodes and data must be mirroring between them so capacity is a half less compare to other SAN technology (e.g.Equal Logic). Is it true? Can a HP lefhand SAN be used as a stand-alone storage server with full RAID function (1, 10, 5)?

TIA, -giobuon

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Depending on your requirements, you might also consider the MSA2000 from HP. It has less features than the LeftHand units, but supports dual controllers, so you've got redundancy should one go bad. –  Chris S Jun 9 '10 at 18:31
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2 Answers

up vote 4 down vote accepted

It can be used as a stand-alone, but you set yourself up for failure by doing so. The Lefthand solution is like a networked RAID configuration. If you purchase just a single node, and it fails (as sometimes happens with any server), you are down. Additionally, there's a severe limit to the number of spindles they can handle, so performance bottlenecks very quickly in a high-throughput application - you wouldn't want to put any SQL servers on here for instance.

A really important question here is, what are your intentions for a SAN? The correct solution very much depends on your intended application...

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Exactly right, can be standalone, can be clustered with or without replication. Good point at the end too :) –  Chopper3 May 20 '10 at 13:33
Thanks for your answers. I've never touch a HP Lefthand SAN so I got many confusions. Does one unit of Lefthand SAN contain two chassis? So is it Network-RAID between two chassis? is it support RAID-5 (network RAID). If I have a HP P4300 with 16x1TB hard drive, can I have a RAID-5 configuration and get 15TB usable storage capacity? –  Gk. May 20 '10 at 15:39
Ok, I found smth maybe useful: tdonline.com/hp-lefthand/storage-calculator So HP RAID 50 is RAID 0 on one chassis and network-RAID 5 over two chassis, isn't it? –  Gk. May 20 '10 at 16:32
Each unit is a single server. At least, as far as I know - our LeftHands were re-branded Dell servers, but I know they are owned by HP now. I took a look at that calculator - it's not particularly helpful. I gather though that RAID 50, in their calculation, is RAID 5 on one chassis, and RAID 50 if striped across 2 chassis. I'm not positive about that though. Chopper3 - thanks! –  Jes May 26 '10 at 14:41
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I host the site with that calculator. It can be confusing:

1) the 8 bay units (p4300 models) are mode from a single RAID 5 array 2) the 12 bay units (p4500 models) are 2 RAID5 that are striped (RAID 5 + 0) or RAID 50

What my calculator is showing is simply the HARDWARE RAID of the individual storage modules.

If you have more than 1 module in your cluster you have the option of doing Network RAID 10 (network striped, 2-way replication) that will consume 2x capacity, but allow a single node failure without your storage going offline. The network RAID level can be configured on a per-volume basis, so you can run higher redundancy for more important volumes, or less for archival etc.

Capacity and throughput scale with the number (and type <7.2k MDL vs 15k SAS>) of drives and number of modules.

The total number of spindles does NOT have a practical limit, as you can continue to add modules to your cluster to increase througput.

The 16TB P4300 you are refering to is the Starter MDL SAN solution. It is made up of (2) chassis, each with 8x1TB drives. If you use Hardware RAID 5 on each module, after formatting and overhead you have a total of 12.48TB usable of Network RAID-0 or 6.24TB of Network RAID-10 (or any combination of the 2, since the Network RAID level is configurable on a per-volume basis)

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