Built for comfort, not for speed
Dell/EMC's iSCSI AX100i makes storage networking easy and affordable but slowFollow @pvenezia
Each server connecting to the AX100i must be configured with an iSCSI HBA or a software iSCSI initiator, and the Navisphere server configuration application must be run on the server to associate the server with the array. Both of these steps went without a hitch on Windows Server 2003 and on Linux. Although Dell does not officially support Linux hosts on the AX100i, they are perfectly compatible. In fact, the management CD shipped with the array contains the required initialization and server management applications for Linux.
Need for speed
On the Windows side, mounting SAN volumes on a server with redundant paths to the array requires EMC’s PowerPath. This is standard operating procedure, and presented no surprises. The Windows server accepted a single path to the SAN, and PowerPath held down the redundant path as expected. The AX100i can support eight servers with redundant paths, for a total of 16 connections. You can easily implement snapshot features for quick data recovery.
Unfortunately, the ease of installation and configuration of the AX100i comes at a price. Features you would expect to see in any iSCSI SAN solution -- jumbo frame support and flowcontrol settings on iSCSI ports -- are MIA. Nowhere within the Navisphere Express console were these settings available for inspection or modification. These controls can have a significant impact on the performance of an iSCSI SAN. In the case of the AX100i, their absence crippled SAN performance.
Ping tests showed the iSCSI ports unable to handle packet sizes larger than 432 bytes, bringing median performance of the array to between 30MBps and 40MBps on both Windows and Linux. (I tested the SAN using software iSCSI initiators and a Dell PowerConnect 5524 gigabit switch with jumbo frames enabled.) Dell claims that the next revision of the AX100i will include jumbo-frame support. That should bring a significant performance boost to this array.
Today, however, the AX100i delivers a level of performance comparable to many simple NAS devices, but nothing close to a well-implemented SAN. As a result, it’s frankly unsuitable for high I/O applications, such as Microsoft Exchange or SQL databases. You might use it effectively for tasks with lighter performance requirements, such as data archiving and file server storage -- but for applications requiring consistently fast access to volumes, you should look elsewhere.