Bad CPU Performance after Linode Resize, Because of unallocated Disk Storage?

I recently updated a Linode-2GB to a Linode-8G.
The Linode-2G had initially come with 30GB Storage.

On the Linode-Dashboard for the Linode, was an option to upgrade the storage capacity of the Linode-2G from 30GB to 50GB.
I initiated and successfully completed the storage upgrade, but did Not allocate the additional storage to the Linodes Disk and Swap partitions.

I then proceeded to do a Linode-Resize from Linode-2GB to a Linode-8G.
The process completed successfully, but again I did not bother to allocate the additional storage space that came with the Resize.

So my space allocation would be sitting at
Disk: 30GB, Swap: 256 MB, Available: 160GB

The Linode had been running a MySQL server, and the performance had been alright
~ i.e. as monitored though Longview, and "via ps,top,iotop" commands.

But as it sits now, without having made any changes to the MySQL configuration, the performance has gotten much worse;

The total CPU% usage now varies from 100% - 150%, with CPU time spent in Wait, using the majority of resources.

Running "free -m" I see I should have plenty of RAM available.

In running "iotop", I see command "[jbd2/sda-8]" taking up at least 50% I/O at any one time.

I've read some articles that mention high "jbd2" I/O operations is an indication of a bad-raid configuration, or generally just a bad configuration of the Disk resources.

I've looked through the Troubleshooting guide to aid me thus far.

That all said, this leads me to think that the reason for the problem is that because I never allocated any of the additional Storage resources, the Linode is now running in an inefficient state as a result.

Am I correct in thinking this? Will allocating the rest of the available resources fix the issue?

2 Replies

"I built a new garage; is that why my water heater isn't working well?"

These are completely unrelated things. The jbd2 process is responsible for maintaining the ext3/ext4 journal; if it's doing a lot of I/O, that means you're doing a lot of disk operations that require journaling (by default, this is everything except actually writing data to disk; eg, creating files, deleting files, etc). If you're seeing a lot of iowait, that could be an indication of noisy neighbors doing a lot of I/O themselves.

Thanks for the reply @dwfreed;

It turned out the source of the increased Wait loads for the jbd2 process were due to some of the in place MySQL configuration/log settings I was using from before.
Relaxing them as much as possible, I was able to significantly bring down the CPU% with respect to the Wait Loads.

I'm not convinced however that the migration of the server from the upgrade was unrelated to the performance degradation;
Though reallocation of the disk space is probably unrelated, I think Linode probably has performed some hardware changes related to thier current server offerings


And assuming an upgrade would migrate the server to a new VM on potentially new Hardware, the configurations that I had in place were no longer optimal.


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