SaaS data loss: The problem you didn’t know you had

CLARRiiON and Celerra arrays have the ability to automatically move chunks of data inside logical volumes from slow to fast access storage tiers and back again.

FAST (Fully-Automated Storage Tiering) currently moves entire logical volumes (LUNs) from, say, high-capacity but slow SATA disk drives to faster drives when the LUN has a high access rate. However, not all data in a LUN is uniformly needed at the same rate. It makes sense to promote only the high-demand chunks of the LUN to faster, and more expensive, storage tiers such as solid state drives (SSDs).

Finer granularity is better for such tiering and the gold standard here is Compellent's block-level tiering called Data Progression. IBM and 3PAR have both recently introduced their own sub-LUN automated data movement in their arrays, making it pretty much a standard feature of enterprise drive arrays.

FAST 2 is integrated with EMC's Unisphere management software for CLARiiON and Celerra for scheduling and configuring it. Unisphere can be used directly or through VMware. It's been refreshed too, with some reports being generated up to 18 times faster than before.

With FAST 2 data can be automatically compressed by the drive array controller at block-level, and this would typically be done with inactive data on SATA drives, releasing disk capacity for other use.

Another new feature is FAST Cache for CX4 CLARiiONS and Celerra NS arrays, using their SSD storage tier to cache read and write data during what EMC calls unpredicted spikes in application workload. This indicates that FAST 2 may not respond quickly enough to a sudden increase in access rate for a particular piece of data, with FAST Cache overrides the auto-tiering policy in FAST 2, scooping up in-demand data and caching it.

ThIs is comparative to controller SSD caching as offered by NetApp with its PAM (Performance Acceleration Module). The only effective difference is the location of the SSD cache; in the controller with NetApp, and in the array with EMC.

FAST 2, FAST Cache and the new UniSphere will arrive in the third quarter of the year. ®

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