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July 2017, Vol. 16, No. 5

Caching vs. tiering: Comparing storage optimization techniques

The difference between the fastest and slowest server storage is huge. Response time for an Ethernet-connected iSCSI SAN system can be six or seven times that of RAM or 3D XPoint. What takes nanoseconds for RAM can take less than a microsecond for 3D XPoint or PCI Express nonvolatile memory express SSDs, milliseconds for SAN storage and as much as 100 milliseconds for disk-based SAN or NAS systems. From the fastest to the slowest, that's a factor of millions of times. Given that disparity, tiering or caching storage optimization techniques can make an enormous difference in an enterprise's active data performance. Deciding which to use is more complicated than simply picking one or the other, however. For instance, with tiering, new storage systems and data management methods have made it more complicated than just dividing data into hot, warm and cold tiers. And with caching, the approach -- write-around, write-through or write-back and server-side or appliance -- that's right for your systems depends on several factors, ...

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