8464ch12_Performance.fm Draft Document for Review February 7, 2020 4:43 pm To determine the number of drives to set, consider MB/GB written to a pool, compute MiBps,  compute maximum and average, and the number of premigration drives per pool. Base the  number of drives by using 50 - 70 MBps per drive for models up to the TS1140, approximately  100 MBps for a TS1140, and approximately 140 MBps for a TS1150. These values are  different from the native data rate because of the resources that are used by a TS7700 (for  example, database updates and logical volume selection for premigration).  Because a Copy Export operation requires each physical volume to be exported to be  mounted, the best approach is to run the operation during a slower workload time. Avoiding Copy Export during heavy production periods 12.8.3 Number of back-end cartridges 12.8.4 Tuning of the usage of Back-end cartridges with VEHSTATS Reclaim value The number of needed back-end cartridges is determined not only by the amount of data that  is stored on the cartridges. The following parameters also can influence the number of  cartridges you need: GLYPH<SM590000> Reclaim value  GLYPH<SM590000> Number of physical pools and pool properties GLYPH<SM590000> Delete Expire setting To monitor your situation and the trend of the cartridge usage, several possibilities are  available, which are described next.  Several possibilities are available to influence the number of used backend cartridges.  As explained in the “Defining reclamation settings in a TS7700T” on page 544 back-end  cartridge section, you can change the reclaim value to gain more empty cartridges. The lower  the percentage of the reclaim value, the more cartridges are needed. The higher this value is,  the more valid data needs to be transferred and physical tape drives are required.  To find a good balance, review the active data distribution. At times, it is sufficient to change to  a slightly higher reclaim value.  For each physical pool, two empty cartridges often are kept inside the pool. Especially for  smaller capacity configurations with large capacity cartridges such as JD media, larger  number of cartridges is needed even if you do not want extra capacity.  In addition, the pool properties should be reviewed.  No borrow/Keep  has a negative influence.  The delete expire value in the scratch categories defines how long a logical volume and the  data on it is still be treated as valid data. For more information about delete expire, see 3.3.8,  “Logical Volume Delete Expire Processing ve rsus previous implementations” on page 123. Note:  A short delete expire value might reduce your cartridge usage, but a short value  does not enable you to rescue any unintentional deleted data. We suggest not to use a  value below 5 days. A best practice is to use 7 days.  734  IBM TS7700 Release 5.0 Guide Amount of physical pool and pool properties Amount of physical pool and pool properties