MiraLink Corporation’s MiraLink 400 is a remote data-mirroring appliance
designed to be a part of a business continuation–disaster recovery plan.
The appliance is a desktop unit with internal Serial ATA (SATA) disk storage.
(Other MiraLink remote data-mirroring products support internal SCSI disk storage
or external SCSI arrays.) The MiraLink 400 is designed for use in pairs, and
each appliance in the pair has its own network connection.The primary MiraLink
400 unit, called the Source unit, connects to the application server at the
local site.The Source unit mirrors data written to it in real time over a standard
IP connection to the secondary unit, called the Destination unit, which is connected
to a backup server at a remote site.
To the server it’s connected to, a MiraLink unit appears as a disk drive.
Units typically connect to the application server through a SCSI interface,
but Fibre Channel, iSCSI, and NAS connections are also possible. As a SCSI device,
the MiraLink is supported in a variety of Windows and other OS environments.
The MiraLink 400 isn’t Microsoft-certified for a Windows or SQL Server
environment—it hasn’t been tested to qualify for the Designed
for Windows (DFW) logo program. However, MiraLink Corporation supports the appliance
in most environments that support SCSI disk storage.
You configure MiraLink volumes by using the Microsoft Management Console (MMC)
Disk Management snap-in. You can also use MiraLink 400 storage to mirror an
application server’s system and boot disks to maintain a bootable copy
of the application server at a remote site.
In Windows environments, data on the
destination unit is not available while the
source unit is actively mirroring to it. In
UNIX and Linux environments, MiraLink
supports read-only access to data on the
destination unit during active mirroring.
To configure the MiraLink 400, I used two identically configured Windows Server
2003 systems with Adaptec 29160LP SCSI controllers.To speed up creation of the
initial mirror, MiraLink Corporation suggests that you initially set up the
units on the same network subnet, then ship the Destination unit to its remote
location. Physical setup consisted of connecting each MiraLink 400 to its server
with a SCSI cable and cabling each server and each MiraLink appliance to an
Ethernet switch. Using Microsoft Internet Explorer (IE) to connect to each MiraLink’s
Web-based UI, I configured the appropriate IP addresses.
I tested the MiraLink 400 for use with database applications by installing
SQL Server 2005 on both the test Source and Destination servers .I installed
an application that relies on SQL Server on a third system, placing the application’s
database (both data and log files) on a 20GB volume on the MiraLink 400 Source
unit. I caused the application to write more than 100,000 records to its database
tables. Using both SQL Server Management Studio and the application’s
GUI, I monitored changes to the database. After causing the application to write
to the database, I unplugged the network cables from the Source MiraLink 400
and its server, simulating a source application server outage.
To use mirrored data on the Destination unit, you use the Web UI to change
the Destination unit’s role to that of a Source unit. To test the mirrored
database data, I changed the Destination unit’s role and started up its
server. Disk Manager reported the MiraLink 400’s storage as a foreign
disk, so I imported it and reactivated the 20GB volume. Using SQL Server Management
Studio (SSMS), I attached the application database and reconfigured the application
server to use the instance of SQL Server 2005 on the new (originally Destination)
server. Using both the application’s GUI and SSMS, I confirmed that the
database updates I had generated prior to the simulated failure were present
on my backup SQL Server.
The MiraLink 400 worked as advertised. The appliance is remarkably easy to
install and use. I wasn’t equipped to perform rigorous SQL Server compatibility
testing to demonstrate the MiraLink 400’s utility as a target SCSI storage
device or as a 100 percent reliable mirroring appliance. I recommend that the
MiraLink 400 be paired both with an application that doesn’t require
more I/O capacity than the appliance can handle and a network connection that
can keep up with the resulting data stream.
MIRALINK 400
PROS: Very easy to install and configure; looks like a SCSI drive to the server
CONS: Windows access to remote mirror during active mirroring isn’t supported
RATING: 4.5 out of 5
PRICE: $2491 to $2932 per unit, depending on amount of storage
RECOMMENDATION: I recommend MiraLink 400 for SQL Server users with one caveat: Test it with your implementation to make certain it will handle your application’s I/O loads.
CONTACT: MiraLink * 503-621-5100 * http://www.miralink.com
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