Flash Pool is the newest addition to the NetApp Virtual Storage Tier and will be available in ONTAP 8.1.1 7-Mode and Cluster Mode.
- SSD and HDD can be combined to form a single aggregate.
- Only one type of SSD and one type of HDD can be in a Flash pool. You can have SSD + SATA, or SSD + SAS, but NOT SAS + SATA.
- SSD will be in a separate raid group to the HDD and must be same RAID type.
- SSDs cannot be removed from the pool without destroying the aggregate, nor can they be reversed into a normal aggregate.
- Flash Pools are only 64bit aggregates. Cannot create or convert from a 32bit aggregate. If you convert a 32bit aggregate to 64bit, then it can become a Flash Pool.
- A new aggregate option hybrid_enable allows the conversion (7 -mode)
- storage -aggregate -modify is used to set a -hybrid_enabled true option. (Cluster Mode)
- Read and Write caching can be modified for different workloads at a volume level using priority hybrid-cache command. FlexShare is also supported.
- An existing SSD aggregate cannot be converted into a Flash Pool.
- The SSDs do not add any usable capacity to the aggregate, it is used for read and write caching only.
- You can mix SSD and SATA on the same DS4243 disk shelf, but you cannot mix SSD and SAS in the same disk shelf.
- ONTAP uses TRIM and native wear levelling and garbage collection mechanisms on the drive.
- Data is maintained in SSD based on usage. You cannot specify or pin data to the SSDs.
- Deduplication and Compression are supported in a Flash Pool.
- Flash Pools are not supported on the FAS2040.
- sysstat -d will break down the SSD and HDD activity for performance analysis.
- Flash Pools do not support SnapLock.
- Flash Cache and Flash Pools are supported on the same system, but the FlashCache will cache data for all non-Flash Pool aggregates. Flash Cache ignores volumes and data in Flash pools. There are limits on a system basis to the total amount of FlashCache and Flash pools when combined.
Flash Pools are recommended for:
- Effective at read caching random reads
- Offloading random writes from disk
- Thus any application that presents random reads and writes as a large part of its workload
Flash Pools are not recommended for:
- Pure SATA aggregates that satisfy their performance requirement
- If an application uses a very large read or write working set (not cacheable workload)
- If the application is completely sequential read or writes.
-Amirul Islam, Storage Practice Manager