Overview : Nytro MegaRAID Software Features : Thermal Management

Thermal Management

In any enclosed server environment, the endurance of the Flash drives depends upon the thermal conditions under which they operate. It is a challenge to keep the Flash drives under the ideal temperature to function. The intelligence in the Thermal Management feature helps reroute the reads or/and writes onto Nytro Cache drives and thus maintains Flash drives under optimal temperature. This tremendously improves the life of Flash drives regardless of Flash types (SLC or MLC). The following block diagram depicts the Thermal management theory.

During I/O, if the temperature of at least one of the Nytro Flash modules in a Nytro Cache drive group crosses the threshold temperature condition, Nytro MegaRAID firmware bypasses caching by not writing the host data onto Nytro Cache drive. I/O routing is achieved with the help of a I/O routing table that guides the I/O direction either to cache drive or to the target volume. The I/O routing table acts as a router, which is updated based on the number of I/Os per cache drive and in discreet time intervals.

Figure 2. Nytro MegaRAID Thermal Management Block

NOTE  The thermal based I/O routing is applicable only for the Nytro Cache drives, not for VDs created by using the on-board Nytro Cache devices.

Every Flash drive has a threshold value of temperature: warning and critical based on the type of Flash media. Based on these values, the following conditions are maintained to route the I/Os:

*

Critical: Current temperature is greater than critical threshold value.

In this condition, no writes are allowed onto Nytro Cache drive.

*

Warning: Current temperature is greater than warning threshold value and less than critical threshold value.

In this condition, all new host writes are routed to the target volumes.

*

Normal: Current temperature is less than or equal to the warning threshold value.

In this condition, I/Os are allowed on the Nytro Cache drive.

NOTE  In the threshold conditions mentioned in the preceding bulleted list, all the reads are allowed to the cache device if valid data are present in cache.