CommVault – The need for speed, pt 1


Speed and performance is an important capability of a Data Protection solution. Most people logically attribute this to being able to finish all tasks in a defined “window“.

I’ve used CommVault for a long time and it’s one of my all time fav’s. It truly does “what it says on the box”.  I’ve also been successful in tuning it effectively to ensure that backup jobs, as well as restore jobs run at consistently good speed.

Heres my  top 3 performance tips;

  1.   Use SSD/Flash to host your DeDuplication Databases “DDB’s”.

In any CommVault installation where DeDup is enabled, the DDB’s get HAMMERED. It is the single biggest cause of bottlenecks in an environment.

The speed of a DDB can be measured by it’s QI time, which is Query & Insertion time. Basically this is how fast the DDB’s can process lookups/queries and inserts. The higher the QI time, the slower the jobs run.

Example. Here is a QI time measurement from an average sized DDB @ ~200GB. This is running off 8 x 15k disks in RAID 0, which ordinarily sounds capable.

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Notice the red microsecond figures. These are meant to be less than 2ms (2000 microseconds). The QI time should not exceed 80% of the threshold in a 14 day period, otherwise no more subclients can be added to the associated Storage Policy, to prevent performance degrading further. As always, red is bad.

Here is the same DDB running off a FLASH based Pool. (a 4+1 RAID 5 on a EMC VNX2),

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That’s a 20 fold decrease in Qi time, and allows me to get consistent results in all types of jobs, including Aux copies;






2.    The second important functionality is to enable “Spill & Fill” for your mount paths.

This is a quasi load balancing that will disperse writers across available mount paths, as opposed to fill and spill’ which will fill a mount path before moving onto another.

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This is applied per library (MagLib) via it’s Properties and “Mount Paths” tab.

3.     Lastly enable “Use unbuffered I/O” for each Mount Path/point

This works on Windows Media Agents only and bypasses the OS file system buffering. It only works on locally mounted block devices, so no unc paths.

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Note that these are only a few of the available options for tuning. There’s a complete list here. However, these are the 3 that I have found deliver the best bang for buck and observable improvements.

I’ll post my next 3 tips soon, so stay tuned.






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