Clariion: Using Navisphere Analyzer to Optimize Performance for SATA, FC, and EFD

Periodic data gathering (for low system impact) so most values are averages (default archive interval is 2 minutes)

Some statistics are implied by I/O rates

  • Response times are derived and can be spoofed by workloads
  • Measurement would be performance prohibitive

Using the Survey Charts

  • Customize and add the advanced characteristics in the General tab
  • Setup Survey Charts (70% utilization, 100ms response time, 12 average queue length, leave interval at 0 to see when it exceeds thresholds at any time)
  • Setting the threshold will cause those that exceed the threshold to be yellow/red boxes
  • Double-click the lun, and it will open the detailed performance view of the lun
  • SATA candidates (all-green boxes with flat lines are a start)

Storage Processors

  • Properties page
    • Cache allocation (200MB read cache is most you might need)
    • Is cache on?
    • Cache page size
    • ABQL (average busy queue length) – FLARE 26+
  • Utilization <70% in general, peaks ok
  • EFD can be added if <70%
  • What if SP utilization is >70%?
    • Random writes – convert R6 to R5/R10
    • Sequential writes – check stripe optimizations, use R3 or R5
    • Consider bypassing cache for large I/O
    • Random reads – upgrade to bigger controller
    • Big configurations – go to CX4
  • Dirty pages
    • Exceeding high watermarks consistently? Saturating cache?
      • Convert SATA to FC
      • Convert FC to EFD
      • Cache bypass on large I/O
      • R10 on small I/O

Host Ports (front-end ports)

  • 360 MB/s is the practical max for FC
  • 100 MB/s is the practical max for iSCSI
  • For best results, zone your EFD luns to ports not near the maximum

LUN

  • Properties page
    • Check ownership for trespass state
    • Cache hit ratio – the best EFD candidates will have low read cache hit ratios
    • SATA LUN with low RCHR may benefit from FC drives, as FC are much better at random reads
  • Click on the lun in the LUN tab, then click on the RAID group tab, it will open that RG to show which other luns are on this RG
    • Groups with a lot of luns will see very random access, not good for high-speed sequential
  • Critical lun stats
    • Utilization
      • Simply the percentage of time the lun is busy
      • Busy means at least 1 I/O, so need to be careful when looking at utilization
    • Response time
      • Directly affects the user
      • Queue length affects this directly
      • Cache response time – affected by SP utilization and dirty state
      • Disk read response time
        • FC read service time 5 ms
        • EFD read serve time 0.1ms
      • I/O mix
    • Average busy queue length
  • Right-click lun to get I/O distribution summary
    • EFD drives good for small I/O
    • SATA drives good for large I/O
  • Read cache hit ratio (RCHR)
    • Low read cache hit ratio favors EFD
    • High read cache hit ratio favors SATA
    • When the lun is busy, look at the ratio to see where it should reside
    • Then look at the throughput

Disk IOPS per drive (rules of thumb for conservative planning, not maximums)

  • 80 for SATA (large block, sequential, small disk seek distances)
  • 140-180 for FC (small I/O)
  • 2500 for EFD (conservative) (requirements for high IOPS or to keep service times down)

Disks

  • Coalescing is important for good bandwidth, especially SATA (putting small IO together into large IO, typically for sequential write IO)
  • Look at the read/write size for the lun and the disk itself. If the lines match, there is no coalescing. If the read/write size for the disk is higher, then you do have coalescing.
  • Signs of sequentiality
    • High pre-fetch used and RCHR
    • Full stripe writes and stripe size (only relevant for parity RAID)
      • FSW * strip write size = sequential write bandwidth
      • Each disk 256KB * 4 = 4 1 MB/s

Primary Criteria for selecting EFD

  • LUN or disk utilization >70%
  • LUN ABQL >12
  • Response time >10ms
  • Read/write ratio 60% or better for reads (better if 80%)
  • I/O < 32KB

Secondary Criteria for selecting EFD

  • Read cache hit ratio <50%
  • Force flushes consistently >10 (busy cache, circumvent cache for EFD)
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