Hybrid Aggregates

aka “Flash Pools”

What is is

• An Aggregate comprised of HDs&SSDs• Dedicated ssd read & write cache/buffer• Fast. ;)• Available in 8.1

Benefits

• Get more out of HDD. By absorbing costly I/O that would have gone to HDD, the drives are open for more reads or writes. This translates into business value in the following ways:

• Change from performance HDDs to capacity HDDs (for example, SAS to SATA)

• Reduce drive counts to satisfy workload requirements• Provide a prepopulated read cache. The data in the Flash

Pool write cache is also available for reads, further reducing HDD operations.

Creating a flash pool

• aggr create hybrid_aggr 16• aggr options hybrid_aggr hybrid_enabled on• aggr add hybrid_aggr -T SSD 6@100

Read Caching policies

• priority hybrid-cache set vol1 read-

cache=meta (metadata only)• priority hybrid-cache set vol1 read-

cache=random-read (default, don’t change)• priority hybrid-cache set vol1 read-

cache=random-read-write (blocks added to cache for writes are immediately availble, but can be duplicated)

Write Caching Policies

• priority hybrid-cache set vol1 write-cache=random-write

• priority hybrid-cache set vol1 write-cache=none

Monitoring

• stats show -phybrid_aggr

ssd read write read ops write blks rd cache wr cache rd cache wr cache read hit read miss

Instance used cached cached replaced rate replaced rate evict destage ins rate ins rate latency latency

/s % /s % /s /s /s /s

aggr1_FP 25463723 22517078 997993 1262 38 0 0 0 0 631 0 0.64 18.48

aggr1_FP 25445886 22537910 998062 1217 38 142 0 0 0 5457 142 2.01 26.20

aggr1_FP 25454002 22537910 998062 1060 37 0 0 0 0 2915 0 0.71 17.48

aggr1_FP 25456742 22535137 997209 2750 47 0 0 0 0 4961 0 2.90 18.69