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Enterprise SAN for Mac OS X Server, Part 2

 

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December 09, 2004 (Computerworld) -- Setting up a storage-area network (SAN) requires working with Fibre Channel hardware. Unlike Ethernet, Fibre Channel is complicated and requires that each part of the system be certified as compliant. Also, there are certain procedures to follow, even when connecting devices to the network.
With this in mind, I chose to partner with Mario Washington, owner of Reboot Computer Services Inc., a Forest Hills, N.Y.-based integration shop. This was a good move, because we ran into compatibility and hardware problems that would have taken me a long time to diagnose alone; Washington recognized them immediately.
For this column, I wanted to build a SAN based on an Apple Computer Inc. server and Xserve RAID unit.
For the Fibre Channel Switch, I chose to use QLogic Corp.'s SANbox 5200 because of its pervasive interoperability. QLogic's products are certified for use with popular servers, storage and networking products from a wide variety of major manufacturers, including Apple Labs, which has certified the SANbox 5200 as being compatible with its hardware. And Aliso Viejo, Calif.-based QLogic touts setup of its switch as being as simple as point and click.
There are other reasons I chose the QLogic switch. Most important, it's the only Fibre Channel switch that's stackable. Stackable IP switches allow businesses to grow their networks in cost-manageable increments, and a Fibre Channel stackable switch does the same thing. You can start with eight ports and activate them in four-port increments. Each stack supports up to four 16-port switches, for 64 ports at speeds of 2GB/sec. per port. The switches can also be trunked together at 10GB/sec., again with just a point and click, so there's no need to hire a specialist just to manage the SAN switch.
Setup of the SANbox was indeed a breeze, requiring only three steps. From the management software main page, I was able to quickly identify a bad port on a host bus adapter card by looking for the "invalid" vendor.
Enterprise SAN for Mac OS X Server, Part 2
I was also able to easily create zones, which are the Fibre Channel equivalent of a virtual LAN. The SANbox 5200 is really that easy!
Enterprise SAN for Mac OS X Server, Part 2
In order to properly work with an Exabyte Corp. device, I changed the speed of the one port connected to the library (not the ports connected to the drives) from 2GB to 1GB. I later found out that the switch would have configured itself had I not manually set the port speed. Changing the speed was easily accomplished by highlighting the port in the face plate and selecting "Port" from the menu, which brought up the following dialog box:
Enterprise SAN for Mac OS X Server, Part 2
Once the switch was fully configured, I made sure the tape backup library system was properly configured and ready to go. For the backup device, we chose an Exabyte 221L-Fibre Channel, an autoloading Linear Tape Open 2 tape library.
The primary reason I chose the 221L is that it supports Fibre Channel connections to both the tape drives and the robotics, thus keeping the entire system in the Fibre Channel realm and eliminating traffic bottlenecks associated with Ethernet. After all, the goal here is to back up a SAN, and if I had to move any portion of the system off the Fibre Channel switch, the process would slow dramatically.
The 221L holds up to 21 200GB LTO-2 tapes and has two drive mechanisms, providing more than 4TB of storage that's rapidly accessible. The 221L will also read and understand bar coding of library media, allowing a client to move entire volumes off-line and then retrieve them using the 221L "mail slot" and backup/restore software of choice.
Setting up the 221L Fibre Channel was a bit complicated, which is why Boulder, Colo.-based Exabyte offers a certified Exabyte installer to perform setup and installation of its product. Once the product was configured, operation was easy. The unit performed as expected when running tests and during the actual backup and restore operations.
One other selling point for the 221L Fibre Channel -- and the entire Fibre Channel backup line from Exabyte -- is the LTO bar code scanning built into the autoloader. Bar-code recognition allows for easy labeling and recognition of volumes without having to scan the headers of each tape. If your backup software can recognize the bar-code information, media management is simplified.
So far, I've discussed the need for a SAN, design of a SAN and what I used to build my Mac OS X SAN environment. Below is a diagram of the design specifics.

Enterprise SAN for Mac OS X Server, Part 2
Please click on image above to view a readable version.

For my test of SAN backup on OS X, I looked at the various products available. It's no secret that the backup market for Apple has been primarily served by Dantz Development Corp.'s Retrospect for many years. (Dantz is now part of EMC Corp.) It's also no secret that Retrospect is getting a reputation as being long in the tooth and of having problems making a successful transition to both Mac OS X and the new reality of multi-terabyte file storage.
I looked for alternatives that could compete in the enterprise space, seeking something that would work with autoloader tape library systems, is compatible with Fibre Channel and is compliant with Mac OS X Server.
I found two candidates. The first, NetVault from BakBone Software Inc., has a long history of enterprise support in both the Windows and Solaris worlds. I was eager to try them out, but found that the software was still running on an X11 graphical user interface and wasn't Cocoa-compliant, nor did it have open file manager and other utilities for OS X. San Diego-based BakBone assured me that within a year it will have the application completely ported over to Mac OS X, but I felt that introducing X11 on a server is a security no-no. I will try the application when it's fully ready for Mac OS X Server ready.
The other application I found was BRU from Tolis Group Inc. in Scottsdale, Ariz. BRU has been around for 19 years as a reliable Unix backup product and is now fully ported to Mac OS X in both personal and server versions. Installing it was easy, as were the Tolis tape tools, which allow for direct connection and control of the library unit.
Connecting to the Exabyte 221L from BRU showed all the drives and slots:
Enterprise SAN for Mac OS X Server, Part 2
More research into BRU revealed the following:
  • BRU was designed from a data recovery perspective. BRU's leadership mechanisms will detect corrupt bits and make multiple (user-defined) attempts to read the bad area. If they can't, the area is reported in specificity, the media is advanced to the next good BRU header block, and the restore continues. All other tools simply abort the restore when bad data is experienced, thereby rendering any remaining data unrecoverable.

  • BRU Server incurs very little CPU overhead. To ensure the fastest access to protected data possible in case the backup server hard disk drive fails, catalogs are appended to the archive, and their rebuild is an automated process done in minutes -- versus the hours or days needed to manually re-create them using other tools.

  • Data written to the BRU Server disk stage is treated as an actual backup, and checksums are calculated on the metadata and actual data the same as a D2T BRU archive stream. That allows the disk stage to be fully verified for accuracy. Multiple, simultaneous data streams from client systems can be written to BRU Server's disk stage, and after an initial full backup of a client system, incremental backups are virtually transparent at the client-system level.

  • BRU Server provides native support of all tape technologies and library configurations. No costly, special software device drivers are ever needed for the largest silos, regardless of the number of embedded tape drives or tape cartridge slots.

But the best piece I found I have to quote directly from BRU's literature, as this is too special to be edited: "BRU Server licensing policies are rational. Any Server system, regardless of OS, attached to the network is simply treated as a client system so no usurious incremental costs to back up these systems are incurred. Client system licenses are tied to the seat and not to an OS."
As you can see, the BRU software is cost-effective and designed to actually restore a backup. Our tests confirm this to be true. For those of you who have used other enterprise backup packages and not had that success, you will seriously want to consider this package. For Macintosh users, this is the only Mac OS X software that's certified to work on Fibre Channel-based backup devices and is worth a look to implement across your entire enterprise backup infrastructure.
Coming in Part 3, a look at SAN file systems.
Did I miss something? Want to ask me something? Send your questions, comments and curses to y.Kossovsky@ieee.org.



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