Easy Tier is even better than we thought!

Good post from Jim Kelly (thank you) on Easy Tier and the DiskMagic 9.1 (for the simulation)

IBM storage architects and IBM Business Partners are encouraged to use Disk Magic to model performance when recommending disk systems to meet a customer requirement. Recently v9.1 of Disk magic was released and it listed nine changes from v9. This little gem was one of them:

“The Easy Tier predefined Skew Levels have been updated based on recent measurements.”

Knowing that sometimes low-key mentions like this can actually be quite significant, I thought I’d check it out.

It turns out that v9 had three settings

  • low skew (2)
  • medium skew (3.5)
  • heavy skew (7)

While v9.1 has

  • very low (2)
  • low (3.5)
  • intermediate (7)
  • high (14)
  • very high (24)

If I take a model that I did recently for Storwize V7000 customer:

  • 40 x 450GB 10K 2.5″ drives RAID5
  • 5 x 200GB SSDs RAID5
  • plus hot spares
  • 16KB I/O size
  • 70/30 read/write ratio

The v9 predictions were:

  • 12,000 IOPS at light skew (2)
  • 13,000 IOPS at medium skew (3.5)
  • 17,000 IOPS at heavy skew (7)

I have generally used medium skew (3.5) when doing general sizing, but the help section in Disk Magic now says “In order to get a realistic prediction, we recommend using the high skew (14) option for most typical environments.  Use the intermediate skew level (7) for a more conservative sizing.”

The v9.1 predictions are now:

  • 12,000 IOPS at very low (2)
  • 13,000 IOPS at low (3.5)
  • 17,000 IOPS at intermediate (7)
  • 28,000 IOPS at high (14)
  • 52,000 IOPS at very high (24)

Read on here

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