The iSCSI EMC AX150i is resold by Dell, and refurbished versions are available pretty inexpensively through the Dell Outlet. We just picked up our second AX150i with 12 500gb SATA drives for around $6,000 total, or about $1,000 per raw terabyte. It’s a great deal for lab or development storage, but there are a couple of gotchas that I haven’t found in other reviews.
Drawback #1: Drive Pool Setup Limitations
The AX150i stores its operating system on the first four drives (bays 0, 1, 2, 3). Those 4 drives therefore have less available capacity than the other 8 drives in the AX150i. Those drives cannot be used as hot spares, either, because of their specialized roles.
This breaks the AX150’s drives into the following categories:
- Disks 1-4: some space consumed by OS, can’t be hot spares
- Disks 5-11: full amount of free space
- Disk 12: hot spare (could be any disk number, but I’m picking 12 for this example)
If the user tries to create a disk pool, and tries to mix some of disks 1-4 with disks 5-11 (like creating a 6-disk array with disks 1, 2, 3, 4, 5, 6), the AX150 throws out a stern warning. It will allow the configuration, but the warning is pretty ugly.
So if the user can’t mix drives from those 3 groups (OS, empty, hot spare), that basically leaves the following possibilities:
- One pool with disks 1, 2, 3, 4 - can either be raid 5 (roughly 1.5tb capacity) or raid 10 (1tb capacity)
- One pool with disks 5, 6, 7, 8, 9, 10, 11 - an awkward total of 7 disks, meaning raid 5 (3tb capacity) or only use 6 disks in a raid 10 and get 1.5tb capacity plus an extra hot spare
- One hot spare (or two, if disks 5-10 were used as a raid 10)
Total config space for raid 5 is 4.5tb, and for raid 10 is 2.5tb. That space quantity is fine, but the hard-coded setup limitations on which disks can be grouped together are a pain - especially when we’re only dealing with 12 drives.
Drawback #2: No Load Balancing
The AX150i has two iSCSI ports, and it does support multipathing with the stock Microsoft iSCSI initiator. I’ve successfully set up both of the iSCSI ports on the same switch, set up two network cards on a Windows server with the MS iSCSI initiator, and then pulled various network cables out during I/O activity. Sure enough, the drives fail over without loss of connectivity or data. To me, that’s an astounding bargain at the sub-$10k price point.
However, with one Windows server and one AX150i, I haven’t been able to break the 90mbps bottleneck - meaning, I don’t get more than one network card of throughput. I’ve tried multiple disk pools, tried multiple drives, different drives on different network ports, and I haven’t been able to figure out how to get it to use two full network ports.
This is not a huge problem at this price point - I’m thankful enough that I’ve even got failover in an array this inexpensive. However, consumers need to be aware that two iSCSI ports doesn’t mean two 1gb network cards with 100% saturation.
Drawback #3: Not Expandable
Dell/EMC don’t claim this model is expandable, but this needs to be emphasized to the prospective buyer. Shops with two or more AX150’s can’t combine them, and can’t migrate data from one AX150 to another. If there’s a small amount of free space on two AX150’s, it can’t be combined to create a single LUN.
Again, not a big problem at this great price point, but something to be aware of. This feature is available at higher price points from companies like EqualLogic (now owned by Dell) and LeftHand Networks.
My Verdict: A Big Winner At This Price Point
Shops that haven’t invested in shared storage yet can get their feet wet with an AX150 without a big capital commitment. I’d recommend it for a shop that isn’t sure whether or not they’ll go with iSCSI or fiber down the road, or if they’re just not sure about shared storage, period. This class of storage is cheaper to get into - and out of - than a LeftHand chassis. An AX150 can be had for under $10k, whereas the LeftHands and EqualLogics run at least twice that much. Granted, they offer twice as many features and much better scalability.
We took the approach that these are for development sandbox use only, never production. Our VMware lab farm is hooked up to an AX150, and so is my SQL Server data warehouse testbed. It’s a testament to their ease of use that I’m always tempted to slap a production array on one just because we’ve got the extra space.
