| Utility ensures 24x7 operations with RAIL backup |
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Multiple backup tape copies and a
redundant array of independent libraries (RAIL) provide continuous operation and data
protection.
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| By Dan Murphy - InfoStor, (for original
article, click here) |
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| Ameren--formerly Union Electric--is one of the
country`s largest public energy utilities, serving more than one million customers in
Missouri, Illinois, and Iowa. As with any utility company, Ameren is critically concerned
with keeping operations running 24x7, placing an extremely high priority on systems and
data availability. To meet that objective, Ameren`s |
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| corporate policy requires duplicate copies of
all backup tapes so that a copy is kept safely off-site in case of a catastrophic data
loss. |
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| Ameren`s computer installation at the
company`s St. Louis headquarters encompasses 1,500 nodes with 120 heterogeneous file
servers running Windows NT, NetWare, Solaris, and HP-UX. All departmental data, along with
custom applications developed for time reporting, customer service systems, and outage
management is backed up nightly to two centralized tape servers. |
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| Ameren uses two Hewlett-Packard LXe Pro
servers operating as backup servers, with each server backing up 60 file servers. The
installation generates a nightly incremental backup load of up to 100GB and a weekly
full-system backup of 400GB to 500GB. Each centralized HP tape server is connected to two
Storage Technology 9714 tape libraries, equipped with 4 or 6 DLT7000 tape drives and 100
tapes. For backup software, Ameren uses Legato NetWorker. |
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| Ameren`s IT staff tried to satisfy the
corporate dictum of duplicate backup tapes with NetWorker`s tape cloning feature, which
provides off-line tape-to-tape copy functions after the backup process is completed. |
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| The tape-cloning feature enabled Ameren to
create a set of off-site backup tapes, but not without a hitch, according to Vance
Bufalo,
senior engineer in networking engineering at Ameren. |
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| "My servers are doing so much work every
night, and the off-site tape has to be ready for pickup by 11 a.m. I didn`t have time to
do the backup at night and do the tape-to-tape copy in the morning before the vendor
showed up to pick up the tapes," Bufalo explains. |
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| "The other problem I ran into is that the
two tape systems support approximately 1,500 users in our main office complex, and we do
recovers on a daily basis. If the tape drives are tied up doing tape-to-tape copies during
the morning, they are not available for tape recovers. I needed a solution that provided
real-time tape mirroring. As one tape is being written, a second tape is being
created." |
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| The need to do real-time tape copying led
Ameren to Ultera Systems (Laguna Hills, CA) for a real-time tape mirroring solution
centered on Ultera`s ShadowMaster tape controller technology. A mirrored tape architecture
essentially creates a RAID-1 environment by simultaneously writing data to a mirrored set
of tape drives. Automatically creating a duplicate set of tapes for off-site storage in
the time it takes to do the original backup solved Ameren`s backup window problem. |
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| Ultera`s tape mirroring controller technology
was also appealing. Because the controller is software independent, Ameren could continue
to use Legato without any changes. Incidentally, the controllers work with leading backup
software applications for Unix, NetWare, and Windows NT. |
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| For the Ameren installation, the tape
configuration goes beyond simple drive mirroring and includes RAIL (Redundant Array of
Independent Libraries). The RAIL configuration mirrors a pair of STK 9714 libraries. One
library is dedicated to storing on-site tapes and the other is used exclusively for tapes
created for off-site storage. Each pair of mirrored drives is driven by a dedicated
ShadowMaster controller. Another ShadowMaster mirroring controller manages the robotic
media changers in each library. |
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| This approach not only enables real-time tape
mirroring, but also makes media management painless. "We have a 30-day tape rotation
because that`s our data retention policy, and tapes never leave the on-site library,"
says Bufalo. |
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| Ameren`s RAIL solution is designed so that it
is impossible to perform backup operations without creating the required off-site set of
tapes. Read operations read data from tapes in the primary library drive, but if a write
command is issued, the ShadowMaster controller automatically writes data to the two
mirrored drives. If the second drive is not ready, an error message is generated and the
backup process is aborted. |
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| "That gives us real-time mirroring, which
meets our requirements. Off-site copies are ready by 11 a.m., and we can still perform
data recovers from the on-site tape library for the last 30 days without any tape handling
by the operators," says Bufalo. |
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| The library mirroring solution worked so well
for Ameren that it recently implemented a larger configuration, deploying an identical
mirrored-library setup using Ultera controllers with an HP9000 K-Class Enterprise Server
running HP-UX with two STK 9710 libraries. Each library accommodates 512 tape slots and 10
DLT7000 drives. |
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| Still, Ameren has even bigger plans for its
tape libraries. The next step will address the ever-expanding data requirements, not just
backups of the corporation`s 5,000 nodes. The current development plan is to incorporate
Ultera mirroring controllers with large-scale STK Powderhorn libraries. |
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Real-time tape- mirroring controllers simultaneously write
data to two tape libraries, creating a duplicate set of tapes.
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| Dan Murphy is a freelance writer specializing
in storage, in Redondo Beach, CA. |
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| Article
Date: |
InfoStor
- October, 1999 |
| Magazine
Volume: |
3 |
| Issue: |
10 |
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