<<< SUBSYS::SYS$ETC:[NOTES$LIBRARY]OPTICAL.NOTE;1 >>> -< Optical Products >- ================================================================================ Note 818.1 Problems with changing disk platters 1 of 1 TAPE::SENEKER "Head banging causes brain mush" 105 lines 2-APR-1997 10:22 -< standard questions and misc. info >- -------------------------------------------------------------------------------- The customers expectations are correct in the disks whould swap until the I/O is completed for all disks. I remember problems similar to this in the past but no specific product changes have been made, I will try to refresh my memory. For now, I recommend the following: o Use SYS$MANAGER:PERCEPTICS$VERSIONS.COM to generate a list of the LaserStar component ids and please post. V3.3 has a few variant releases. o What is the optical hardware, related I/O interface, and host processor. Is this part of a cluster? If so, are the disks mounted /CLUSTER? o Try changing the MINSWAP and/or IORATE values. Extract from help below: JBUTIL SET PARAMETER /MINSWAP=time MINSWAP is the amount of "time", in seconds, that a disk cartridge will remain in a drive before it can be removed as part of a swap operation. The MINSWAP interval begins after the disk has been inserted and spun up. Once a disk has been inserted into a drive in the jukebox, it will remain in the drive until the MINSWAP interval has expired, regardless of the amount of activity on the disk or the number of other disks waiting for a drive. The minimum value for MINSWAP is 5 seconds. JBUTIL SET PARAMETER /IORATE=seed IORATE is the name used for a seed value used in the jukebox swap algorithm. Large IORATE seed values will help cause heavily used disks to remain in a drive longer than their MINSWAP interval. The IORATE "seed" value is fed into an equation whose result is used to determine if the time the disk will be allowed to remain in the drive will be extended. The larger the IORATE "seed" value the less likely a disk performing servicing many I/O's will be swapped. Very large IORATE values will not significantly increase the amount of time a disk remains in a drive due to the exponential nature of the equation. Setting IORATE to zero will disable this feature completely so that only the MINSWAP time controls swap eligibility. swap_equation The number of seconds for a volume to become eligible to be swap is a function of MINSWAP, IORATE and the number of I/O operations the volume has performed since it has been placed in the drive. The following equation computes an operation rate, which is one of the values used to determine swap eligibility. OPS_RATE = IORATE * OPS / SEC_IN_DRIVE / SEC_IN_DRIVE where: OPS_RATE = operation rate of the volume IORATE = value of the IORATE parameter OPS = total number of operations since the volume was moved into the drive SEC_IN_DRIVE = number of seconds since the volume was moved into the drive The volume will be eligible for swapping when it has been in a drive longer than MINSWAP seconds and the OPS_RATE value is zero. The IORATE Impact on Swap Time Eligibility indicates some example showing how long a volume will remain in a drive based on IORATE and the number of operations per second. MINSWAP is set to five sconds for these examples. Table 1-1 IORATE Impact on Swap Time Eligibility Operations per IORATE Second Eligibility second 1 5 6 2 5 11 3 5 16 4 5 21 1 10 11 2 10 21 3 10 31 4 10 41 Any 0 5 value As another example, if IORATE=2 and the volume gets 500 operations in the first second and is then idle, the swap will not occur until 32 seconds have elapsed. The OPS_RATE will not be greater than zero until SEC_IN_DRIVE equals 32. Also if the OPS value exceeds 1024 the volume will be allowed to swap when MINSWAP seconds has been exceeded. This puts an upper limit on fast drives from preventing other volumes use of the drive. Rob