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Unlabeled SMR Drives May Be Choking Your Throughput

by Seth Noble |  Blog Apr 17, 2020

SMR, Shingled Magnetic Recording, is a hard disk drive technology that provides increased density at the cost of greatly reduced write performance.  While the technology has been around for several years, articles from Ars Technica and Tom's Hardware report that several manufacturers have begun shipping these drives under labels previously reserved for higher performing traditional hard drives.  This can result in devastating losses of performance and connectivity as SMR drives are not only slower, but they reportedly can become unresponsive for long periods of time resulting in hung systems and dropped devices.

MTP software will report underperforming storage devices, but you will need to check your server logs to see these warnings about server-side storage.  Any IOP that takes longer than 1 second to complete will result in a message like this:

WARNING: Filesystem took XXXXms to write XXXX bytes (XXXX bits/s)

If storage is chronically unable to keep up with network speeds, level 1 logging will record "FileWrite: overflow" messages displaying buffer and performance metrics.  Tech Note 0033 has step-by-step instructions for enabling diagnostic logging and running performance tests.  If you are unsure what the output means, contact us.  Even if you are not a DEI customer, you can download a free trial to test your storage.

When you are investigating network transfer performance problems, remember that storage is part of the path.  While SMR drives are rare, for now, other storage problems are a common source of data transfer bottlenecks.  For example, trying to write data to a trans-oceanic SMB mount is never a good idea!

The newest MTP version 4.3 has new features to isolate the effects of underperforming storage in multiuser environments.  But ultimately no software can move data faster than hardware, and a hung system hurts everyone.  If you have recently changed your storage components, perhaps installing a new drive in your array, and are suddenly experiencing slow write speeds or hangs, check the specs on that new drive very carefully.