Testing High Performance Tape Drives

1. Testing High Performance Tape Drives HEPiX FALL 2005 Data Services Section

2. Motivation LHC 2007 ~15 Petabytes/year

3. Current Model RFIO DATA DATA DATA DATA CASTOR HSM DATA DATA

4. Devices Tested IBM 3592JA Tape Drive IBM 3584 Library + + Future Generation Tape Drives >100 MB/s Testing in 2006 300 GB / 60 GB 40 MB/sec 117 carts 12 drives STK SL8500 HP LT0-3 + + 400 GB 1,448 carts 80 MB/sec 64 drives

5. Tape Server Tape Library Test Infrastructure Fiber Fiber Channel HBA Tape Drive

6. Functionality Tests • Go through the set of commands available on the SCSI standard • Check returned information, timing, command acceptance SCSI COMMANDS: Change Definition, Compare, Copy, Copy and Verify, Display Message, Erase, Format Medium, Inquiry, Load/Unload, Locate , Log Select, Log Sense, Mode Select (6), Mode Select (10), Mode Sense (6), Mode Sense (10), Persistent Reserve In, Persistent Reserve Out, Prevent/Allow Medium Removal, Read, Read Attribute, Read Block Limits, Read Buffer, Read Position, Read Reverse, Receive Diagnostic Results, Recover Buffered Data, Release Unit (6), Release Unit (10), Report Density Support LUNs, Request Sense Unit (6), Reserve Unit (10), Rewind, Send Diagnostic, Set Capacity, Space, Test Unit Ready, Verify, Write, Write Attribute, Write Buffer, Write Filemarks

7. fibre channel analyzer for verifying SCSI commands Functionality Tests

8. Linux tape driver and cernTapeTestUtil (interactive/command line mode) Test Scenarios

9. Analysis of Results

10. Mechanical Tests IBM 3592: Over 125,000 mount/dismount cycles performed, no errors Test mechanical reliability of drive / media: some cartridges now mounted > 4000 times, no errors Random file reads on selected tapes and media: superseded by CASTOR operation in data challenges HP LTO-3: Over 125,000 mount/dismount cycles performed, no errors Test mechanical reliability of drive / media: some cartridges now mounted > 5000 times, no errors

11. Performance Tests • Use of native Linux Commands (mt/dd) for data transfers : • read / write • compression / no compression • blocksize • filesize • position “labeled” files

12. LTO-3 Data Transfer Rate Write no compression Performance

13. LTO-3 Data Transfer Rate Read no compression Performance

14. Linear Serpentine Recording Linear Serpentine Recording Technique

15. LTO-3 Locate File Timing Algorithm problem(?) seen older LTO-1 drives, just HP (? ) LTO-3 Locate Record Timing Performance END OF TAPE BEGINING OF TAPE

16. 80 Bytes 0-? Bytes 80 Bytes 80 Bytes 80 Bytes 80 Bytes 80 Bytes Trailer 2 Trailer 1 Header 3 Trailer 3 Header 1 Data Header 2 Tapemark Tapemark Tapemark Sync ANSI Labels Headers Filename, block size, HSM version, time of writing … Number of blocks, non standard data … Trailers Tapemark Special records on tape used by the drive, immediate bit =0/1 Sync Flush buffer

17. Labels vs Performance Minimum over head Maximum over head

18. Labels vs Performance HP-LTO3 IBM 3592JA

19. Labels vs Performance IBM 3592 small files

20. HSM Integration OK Drive integration in HSM system • tape_up tape unit standard testing for production utility • tplabel tape labelling utility • dumptape tape dumping (scanning) utility • stagein tape reading utility • stagewrt tape writing utility • repack move CASTOR file from tape and reclaim utilities Functionality + Mechanical + Performance Castor Production

21. IBM 3592/HP LT0-3: SNMP Agent : Error Counters Tape Alerts Drive and Media: number mounts/Loads/… IBM 3592: Statistical Analysis and Reporting System : bit 62: SARS Drive Relative Quality X'00' is unknown, best X'01' -> worst X'FF‘ bit 63 SARS Media Relative Quality X'00' is unknown, best X'01' -> worst X'FF' No Vendor: Perfect tool for monitoring all type of drives and for a large number of drives Operations Request Sense

22. SAN More Tests RFIO CASTOR HSM $$ ??