HP 12000 HP VLS Solutions Guide Design Guidelines for Virtual Library Systems - Page 63

Sizing/implementation Examples, Example 1 VLS Sizing for Performance and Capacity

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Sizing/implementation Examples There are no standard, generic rules for sizing your environment but there are general parameters that you can use to help you understand your capacity needs. Example 1 VLS Sizing for Performance and Capacity Assume that you have 12 servers being backed up across a SAN. Each is pushing data at 15 MB/sec. You are writing to four LTO2 tape drives, which have a maximum write speed of about 60 MB/sec with 2:1 compressible data. You are not fitting within your backup window. Naturally, you want to use your servers, backup window, SAN, and tape drives/library as efficiently as possible. If the servers are only backing up at 20 MB/sec, you are not streaming the LTO2 drives and the backups are taking four times as long to complete, because you are only using the tape drives at one quarter of their performance. You do not want to send the backups over the LAN because it will cause LAN bottlenecks and you do not want to buy more tape drives. Introduce VLS into your environment. How do you size the VLS in terms of performance and capacity? The average throughput speed of the VLS 6510 base configuration is approximately 225 MB/sec, and the aggregate throughput required by your backups is 180 MB/sec. This fits. But you have additional options. Now that you have determined the minimum configuration of the VLS (by making sure that the performance of the VLS accommodates your aggregate throughput), consider how much capacity you need to have and how you reach that. Of course this requires not only that you understand your base storage needs (what is the size of the full and incremental backups) but that you factor in retention policies. For example, if each host is backing up 400 GB in a full backup and 40 GB for each incremental backup, and if the retention policy for the virtual cartridges is to store one week of backups, and a "week's worth" is one full and five incremental backups, then each host will require storage for 600 GB of data. This would therefore require 7,200 GB of backup capacity in the VLS. There are two methods for achieving this. You can enable compression when you create virtual tape drives, so that the capacity of the base VLS 6510 would be sufficient, but this would not allow for future performance expansion (adding more hosts), since compressed performance is limited to 190 MB/sec even if you add capacity upgrade. The alternative, if you want to allow for future performance growth, is to leave the data uncompressed and add a capacity upgrade to the VLS 6510 to increase the capacity to 7,500 GB (this increases the uncompressed performance as well). Finally, you have to configure copy jobs. If you use the four-drive library for the copies, the VLS will be able to stream the drives. Despite the fact that the copy jobs are going to fewer drives than the backup, the copy time will be approximately equal to the backup time because you're using the drives efficiently. Example 2 Testing Backup to Tape vs. Backup to VLS In this example: • One virtual library (VLS 6105) has been configured with five drives • Servers 1 and 2 have LAN-attached data • Servers 3, 4, and 5 have shared storage resident on the MSA 1000 • The backup application is Data Protector VLS Sizing 63

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Sizing/implementation Examples
There are no standard, generic rules for sizing your environment but there are general parameters
that you can use to help you understand your capacity needs.
Example 1 VLS Sizing for Performance and Capacity
Assume that you have 12 servers being backed up across a SAN. Each is pushing data at 15
MB/sec. You are writing to four LTO2 tape drives, which have a maximum write speed of about
60 MB/sec with 2:1 compressible data. You are not fitting within your backup window.
Naturally, you want to use your servers, backup window, SAN, and tape drives/library as efficiently
as possible. If the servers are only backing up at 20 MB/sec, you are not streaming the LTO2
drives and the backups are taking four times as long to complete, because you are only using the
tape drives at one quarter of their performance. You do not want to send the backups over the
LAN because it will cause LAN bottlenecks and you do not want to buy more tape drives.
Introduce VLS into your environment. How do you size the VLS in terms of performance and
capacity? The average throughput speed of the VLS 6510 base configuration is approximately
225 MB/sec, and the aggregate throughput required by your backups is 180 MB/sec. This fits.
But you have additional options.
Now that you have determined the minimum configuration of the VLS (by making sure that the
performance of the VLS accommodates your aggregate throughput), consider how much capacity
you need to have and how you reach that. Of course this requires not only that you understand
your base storage needs (what is the size of the full and incremental backups) but that you factor
in retention policies.
For example, if each host is backing up 400 GB in a full backup and 40 GB for each incremental
backup, and if the retention policy for the virtual cartridges is to store one week of backups, and
a “week’s worth” is one full and five incremental backups, then each host will require storage for
600 GB of data. This would therefore require 7,200 GB of backup capacity in the VLS. There are
two methods for achieving this. You can enable compression when you create virtual tape drives,
so that the capacity of the base VLS 6510 would be sufficient, but this would not allow for future
performance expansion (adding more hosts), since compressed performance is limited to 190
MB/sec even if you add capacity upgrade. The alternative, if you want to allow for future
performance growth, is to leave the data uncompressed and add a capacity upgrade to the VLS
6510 to increase the capacity to 7,500 GB (this increases the uncompressed performance as
well).
Finally, you have to configure copy jobs. If you use the four-drive library for the copies, the VLS
will be able to stream the drives. Despite the fact that the copy jobs are going to fewer drives than
the backup, the copy time will be approximately equal to the backup time because you’re using
the drives efficiently.
Example 2 Testing Backup to Tape vs. Backup to VLS
In this example:
•
One virtual library (VLS 6105) has been configured with five drives
•
Servers 1 and 2 have LAN-attached data
•
Servers 3, 4, and 5 have shared storage resident on the MSA 1000
•
The backup application is Data Protector
VLS Sizing
63