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Testing IBM TS3500 S24 high density frame

Testing IBM TS3500 S24 high density frame. Vladimír Bahyl September 2008. Overview. Hardware S24 frame IBMLIB3 library Tests Setup Performance measurements Tape distribution algorithm Integration with CASTOR Conclusion. S24 provides. Max. 4 cartridge tiers in high density slot

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Testing IBM TS3500 S24 high density frame

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  1. TestingIBM TS3500S24 highdensityframe Vladimír Bahyl September 2008

  2. Overview • Hardware • S24 frame • IBMLIB3 library • Tests • Setup • Performance measurements • Tape distribution algorithm • Integration with CASTOR • Conclusion Testing IBM TS3500 S24 High Density frame – 2

  3. S24 provides • Max. 4 cartridge tiers in high density slot • 1000 slots for 3592 media • D23: 400 slots for 3592 media • Capacity: 2.5 x D23 • Price: 2 x D23 • Footprint: equal to D23 • Total library storage capacity increase: from 6,200 slots to over 15,200 (preview value) • LED lighting S24 D23 Testing IBM TS3500 S24 High Density frame – 3

  4. S24 – naming conventions Cache T00 T01 T02 T03 T04 1 2 3 4 5 : : : : : : : : : 35 36 37 38 39 40 Testing IBM TS3500 S24 High Density frame – 4

  5. IBMLIB3 overview L23 D23 S24 Drive used for tests was TS1130 E06 in slot 1 • Drives • 3 x TS1130 E06 • 1 x TS1130 EU5 • 2 x TS1120 • Cartridges • JA and JB media • 863 in total • Library • 1 accessor • Microcode: 81au Contains drives All tape slots full Most of the slots marked logically offline All tape slots full Testing IBM TS3500 S24 High Density frame – 5

  6. S24 – test setup 1/2 Testing IBM TS3500 S24 High Density frame – 6

  7. S24 – test setup 2/2 Initial temporary storage area (2 yellow slots at the top) should be kept empty and online during the initial frame audit Testing IBM TS3500 S24 High Density frame – 7

  8. Time to Mount test – objectives • Observe the average time it takes to mount a cartridge from various tiers • Exercise all tiers, including the T0 cache • Measure only mount time (not the drive load time) • Use 100 tapes randomly distributed across all rows Testing IBM TS3500 S24 High Density frame – 8

  9. Time to Mount test – results Drive 1 used = 1st one from the top Column initial temporary storage area = 2 yellow slots at the top. Once they are full, reshuffling takes time. There were physically more cartridges in this area in the neighboring columns. Shows difference in access to between columns Clear penalty – gripper can hold 2 cartridges at any one time, to access anything deeper takes longer Almost no penalty to move a tape from the bottom = very fast vertical movements Testing IBM TS3500 S24 High Density frame – 9

  10. Average Time to Mount ~700 msec difference due to different velocity profile of the gripper when accessing a high density slot ~10 sec difference because the gripper has only 2 cartridge slots Testing IBM TS3500 S24 High Density frame – 10

  11. Cartridge distribution algorithm • Algorithm • Least Recently Used (LRU) • Discards the least recently used items first • Tries to keep busy tapes in cache (tier 0) • Test • Selected 4 groups of 20 tapes from each tier in frame 3 • 20 tapes from tier 0, 20 from tier 1, 20 from tier 2, etc. • Mount the 100 tapes in random order • Check their location after the run finished • Repeat 4 times Testing IBM TS3500 S24 High Density frame – 11

  12. Cartridge distribution test results No more than 70 cartridges were kept in the cache IBM: cartridges in T1 and T2 are considered as “near-cache” so they are returned to T1 Already after first run, no tapes were pushed into tier 4. Testing IBM TS3500 S24 High Density frame – 12

  13. Issues (related to 81au microcode) • Keep the first 2 rows (yellow sticker slots) online (during the initial frame audit) if there are cartridges in any row of that column – otherwise the library gets confused • Automatic drive cleaning did not work • Cartridge moves by location did not work • Using the small library display Testing IBM TS3500 S24 High Density frame – 13

  14. Integration with CASTOR • All mounts and dismounts were done using SCSI medium changer • rmcdaemon • Complexity of access to the high density slots hidden from the user = transparent for CASTOR • No change to CASTOR required Testing IBM TS3500 S24 High Density frame – 14

  15. Conclusion • S24 significantly increases the capacity of 3592 media frame while keeping the same footprint • S24 = 2.5 x D23 • CERN has successfully measured the access times to all tiers within the delivered high density frame • The access to cartridges in higher tiers is transparent from the CASTOR point of view; no modification to the code is required • The increase of the time to mount cartridges from higher tiers is not going to have any significant impact for the users • CERN is going to use this frame in production • Extend existing libraries • Purchase new libraries with S24 frames as requirements grow Testing IBM TS3500 S24 High Density frame – 15

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