Exabyte Has a Winner with Model 430 Mammoth-2 Tape Library
Newenterprise technologies come and go, but one thing remains constant: Datastorage needs continue to grow at astronomical rates. File storage, mailservers, database server systems, and many more servers form the core of anenterprise’s data repositories. So how much data do you need to backup? Tengigabytes? Fifty gigabytes? That much storage undoubtedly means you use atleast a DDS-3 or DDS-3 changer drive. Even with such a powerful drive, you’llspend a good amount of time and resources backing up the data, not to mentiondoing restorations, and switching tapes all the time.
Onesolution to this problem is a tape library with multiple drives of highcapacity that is armed with plenty of tapes to support the effort. Exabyte hasa tape backup library that fits this bill quite nicely: the Model 430 library,which uses the Mammoth tape specification. We received the Model 430 with two 8mm drives out of the 4-drive slot capacity armed with 30 slots for 8 mm tapes.The tested unit supports up to 225 meter Advanced Metal Evaporated (AME) tapemedia, which has a native capacity of 60 GB and up to 150 GB with 2.5-to-1compression. There are other 8 mm tapes that are supported, but Exabyteconfirms that these AME tapes are self-cleaning and says these have the “rightstuff” for the drives. AME tapes offer the next generation of capabilities andwe recommend that you stick with Exabyte’s recommendation.
The unit camewith two drives, 30 tape slots -- 10 fixed and two sets of 10 in removablecarriers -- and an interface for LVD SCSI-3. The unit came with the chassisinterconnecting cables, media, and manuals. Oddly enough, Exabyte chose to makethe rack mount kit an optional part of the system. At 75 pounds fully loaded,the unit needs a stable mounting system, and Exabyte should send the kit withthe unit.
Weconnected the unit to a dual-processor Pentium-233 MMX Intel-based serverrunning Windows NT Workstation 4.0 with Service Pack 4, 256 MB of memory, and anew Adaptec Model 29160 SCSI-3 controller supporting LVD internal and externaldevices at speeds up to 160 Mbpsec [?B?]. You can run the unit from either aserver or a workstation running Windows NT Server or Workstation, or any otheroperating system that supports SCSI-3 LVD devices. This host PC isinterconnected to the servers via a Cisco-powered Fast Ethernet backbone. TwoWeb servers were located on the private internal network routed by a Cisco 2514router, which performs network address translation to the RFC-1918 network.
Weperformed the evaluation with multiple servers and data repositories. The maindatabase system was Microsoft SQL Server 7.0 sporting nearly 3 GB of databases.Two Microsoft Exchange 5.5 servers were deployed for enterprise workflow andmessaging systems -- one server totaled 3.1 GB of mail repository while theother had 2.2 GB of messaging storage. Each messaging server providedadditional file services for users and FTP Web servers, totaling some 12.7 GBof storage.
These fileswere a mix of documents, spreadsheets, compressed archives, and server-basedapplications such as Microsoft Office. We had additional file and print serversthat provided about 85 Web sites with personal user file storage. Other serversincluded Linux boxes running SAMBA emulation and Sun Solaris servers for Webservices. Overall, the enterprise was host to an excess of 20 GB of data thatwas backed up.
Weinstalled Veritas Backup Exec 8.0 for the enterprise. The product has nativesupport for the Exabyte 430 chassis. During testing, we discovered that VeritasBackup Exec 7.3 and earlier are problematic with the tape drivers. Even usingthe tape drivers on Exabyte’s support Web site didn’t entirely fix the incompatibility.Backup Exec 7.3 has issues supporting the robotics changer. Upgrading toversion 8.0 of the product fixed all problems, and the unit worked flawlessly.
Theinstallation was easy, but heavy. Our chassis weighed close to 80 pounds whenfully loaded. You’ll need a well-anchored rack space of five units, or aboutnine inches. LVD supports up to 15 meters of cabling, so the system can bepositioned away from the backup PC. This is useful because the unit, when infull operation, tends to be a bit noisy when moving tapes in and out of therobotics.
Thephysical configuration is simple: All library devices come preconfigured withSCSI 0 for the library, and 1 and 2 for each individual drive. The Adapteccontroller needs an available 32-bit slot, or one 64-bit slot if your serversupports 64-bit PCI boards. If you only have 32-bit slots, the card works fine.But be sure to turn off parity checking on the Adaptec and on the Exabyte unit.
We definedfour backup sets of data for the test. All tests were designed to exercise therobotics and advanced functions offered by the unit.
* Theentire enterprise of 21.1 GB, spanning every file type possible plus WindowsExchange mail and workgroups, with SQL Server repositories.
* About 1.6GB on the local host PC plus 9.3 GB of FTP server archives across the network.
* Backingup both Exchange mail server repositories across the network, plus restoring900 MB of data files on the host PC.
* Performingtape erase functions on multiple tapes while searching old catalogs for, thenrestoring, SQL Server databases.
The firstpass of the tests all used a 1 K block size for the tape, with a 32 K buffer.All backup operations to the local machine averaged 87.4 Mb [?B?] per minuterate with no errors. Backups across the LAN averaged 89.1 Mb [?B?] per minute,which is somewhat slower than we had anticipated. We monitored the network witha sniffer and saw no problems at all. In fact, we were surprised that networkutilization was only 7.3 percent of total bandwidth, even with all other normaloperations functioning. All in all, every requested function worked flawlessly.
While thedual operations were running, we ran the Windows NT performance monitor toevaluate the impact on the host with dual tape operations with such a powerfulSCSI adapter. Monitoring the CPU, user time, interrupt time, and privilegetime, we saw that both processors were each running close to 61 percentutilization. There were peaks and valleys, but this was a good ballparkobservation. Overall system time in the user and interrupts were very low -- inthe 10 percent range. Repeating this test sequence on a single processor serversaw the server running at 100 percent utilization almost all of the time,resulting in a 21 percent increase in time to complete the tasks. We came tothe conclusion that the entire backup operation under Veritas was multitasking,and doing it quite well given the amount of services we were tasking the Model430 to do.
Repeatingthis test sequence in a second pass, we adjusted the tape block size to 32 Kwith a buffer of 32 K, then with a block size of 32 K and a buffer size of 64K. The change to 32 K block size brought a dramatic jump in backup speeds to122.7 Mb per minute for local host PC backups, and a modest increase to 108.1Mb per minute for LAN backups. More importantly, our particular test bed saw nofurther improvement by increasing the block size to 64 K for the tape or 64 Kfor the buffer size. The block size can never exceed the buffer size.
We furthertested the unit by dropping the tape block size down in stages from 32 K to 16K, then to 8 K, and so on. We saw the overall performance drop accordingly,just as we saw the dramatic jump in performance when the block size was movedfrom 1 K to 32 K. We concluded that choosing a tape block size of 32 K with abuffer size of 64 K was optimal for our enterprise. We suggest that you dosimilar testing to find the optimal performance range for your host PC.
Our lasttest covered manually working with the unit in case a tape got hung up, gotlost in the robotic sequence, or encountered other less than optimalconditions. The user’s manual was a good resource, and we rapidly learned howto test the unit, remove errant tapes, and change the SCSI ID as required.There’s a side port on the right front side of the unit that is used to removeone tape at a time without removing the cartridges from the carriers. Thesingle tape access port is meant for single tape ejection and insertion withoutopening up the front panel. All of these manually operated services via thefront panel worked perfectly.
One lastfunction is available: A software tool for remotely monitoring the operation ofthe chassis. You can’t do much with it, but it worked to our satisfaction. Notethat this is monitoring for the chassis, not the Veritas backup operation thathas its own administrator product.
Our initialimpression was that this chassis was intended for enterprise libraries, and wewere right on target. Exabyte hit a home run with its version 1.0 for thisparticular model. It builds on proven Exabyte engineering, and is sure to be awelcome site in any major enterprise despite the list price of $22,300. Wecalculated that a DDS-3 backup system has a capital cost of about $58 pergigabyte, whereas the Model 430 unit comes in at $12 per gigabyte of capacity,when considering the hardware alone. If you can get by the initial capitalcosts, the downstream savings are as phenomenal as the performance of thechassis itself.
Model430 Mammoth-2 Tape Library
Exabyte Corp., Boulder, Colo.
+ Blindingfast backups of large data repositories
+ Supports concurrent backup/restore operations with two or more drives
+ Excellent software support for enterprise backup systems
- No rackmount kit provided
- Highoverall cost