2010-07-07 01:59 AM
I am calculating SMSQL snapinfo size now.
There is the following descriptions in TR-3768.
BASE_VAL: Sum of the current log file sizes of all the databases in the instance.
N: Determine the maximum number of TLOG backups per database
LUN size = BASE_VAL * N.
There is the following descriptions in TR-3779.
SnapInfo_LUN_Size = ((DB_Size * Daily_Chg_Rate * Days_per_TA-Log_Snapshots)
Which is the correct ?
2010-07-07 04:19 AM
We've found that the size needed for Snapinfo is greatly affected by whether the databases are Full or Simple model. In full model, all the tx logs are stored in Snapinfo for the duration of snapshot retention, so your first calculation is appropriate.
With Simple model, the tx logs won't be placed in Snapinfo, so the Snapinfo LUN can be much smaller.
If you have a mix of both types within the system, size for Full.
So the calc we'd normally use is:
Logs size * num of logs online to keep + a bit headroom for streamed system databases.