Log Insight: Live Storage vs. Disk Size

I was recently asked to explain a discrepancy between the reported live storage size reported by Log Insight versus the actual disk size listed on the Log Insight virtual appliance:

LogInsight_Space_Discrepancy

As you can see in the above screen shot, the delta is rather significant (almost 40 GB!). So what is going on?

If you compute the Used and Avail numbers reported by the “df -h” command you will notice they match the number reported under the Live Storage section of the Log Insight UI. What you are seeing is filesystem specific and not a Log Insight issue. While the virtual disk is 739 GB in size only 700.7 GB is actually usable space. The remaining 5% + a rounding error is reserved by the system and is a feature of the ext filesystem. For more information see this (applicable to ext3 and ext4 as well) link.

Reserved Space
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In ext2, there is a mechanism for reserving a certain number of blocks
for a particular user (normally the super-user). This is intended to
allow for the system to continue functioning even if non-privileged users
fill up all the space available to them (this is independent of filesystem quotas).
It also keeps the filesystem from filling up entirely which helps combat fragmentation.

© 2014, Steve Flanders. All rights reserved.

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