HP XP Racks - Manual (Page 67)

2. Calculate the time necessary to back up a database using this formula:
DB_BACKUP_TIME = {( IS / IS_VERIFY ) * IS_NUM + ( LOG_NUM / LOG_VERIFY )} * SG_NUM
+ RESYNC_TIME
NOTE:
Because the variables IS_VERIFY and LOG_VERIFY are highly dependent on server and
storage I/O performance, actual values are difficult to obtain. For best results, use the
assumed values supplied.
3. Compare the time allowed for the backup process with the time required to back up a database
server:
• If the SYSTEM_BACKUP_TIME value is less than or equal to the DB_BACKUP_TIME value,
decrease the number of storage groups and/or information stores per database server and
repeat the calculation in step 2.
• If the
SYSTEM_BACKUP_TIME
value is greater than the
DB_BACKUP_TIME
value, calculate
the number of backup servers using the following formula:
BK_SERVER = DB_SERVER / VERIFY_PARA
Round this value to the nearest whole number.
Table 2 Parameters for backup server calculations
Notes Description Parameter
You must supply this value.
Size of a the database file per inform-
ation store to be backed up (MB)
IS
You must supply this value.
Number of transaction log files per
storage group to be backed up
LOG_NUM
You must supply this value.
Number of information stores per
storage group (Exchange Server
2003/2007), or per database server
(Exchange Server 2010)
IS_NUM
You must supply this value. Because
storage groups are not supported in Ex-
change Server 2010, use a value of 1
in this case.
Number of storage groups to back
up per database server (for Exchange
Server 2010, use a value of 1)
SG_NUM
You must supply this value. Number of database servers DB_SERVER
You must supply this value.
Time allowed for backing up the en-
tire system (seconds)
SYSTEM_BACKUP_TIME
You must supply this value based on
Parallel performance .
Parallel verification count VERIFY_PARA
Depends on the performance of the
storage and the server.A value of 50 MB
per second is assumed for the calcula-
tion.
Verification performance of the in-
formation store (MB/second)
IS_VERIFY
User Guide 67