“Incomplete Communication with Cluster” with local Storage Space for SQL Server cluster

When building a SANless SQL Server cluster with SIOS DataKeeper, or when configuring Always On Availability Groups for SQL Server, you may consider striping together multiple disk in a Simple Storage Space (RAID 0) for performance. This is very commonly done in the cloud where each instance typically his backed by hardware resiliency, so RAID 0 is not really all that risky.

For instance, I had a recent customer in AWS that wanted to max out his IOPS to 80,000, the maximum IOPS currently available to a single instance. Now keep in mind, only the largest EBS optimized instance sizes supports 80,000 IOPS, so you want to make sure you know what maximum IOPS your particular instance size supports.

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSOptimized.html

In this case we had ac5.18xlarge instance which does support 80,000 IOPS. However, any individual EBS Provisioned IOPS volume only supports up to 32,000 IOPS. The only way to achieve 80,000 IOPS when writing to any single volume is to strip three of these volumes together in a Simple Storage Space.

Herein lies the rub, if you try to do that in an existing cluster things are going to go haywire pretty fast. Fellow MVP Joey D’Antoni recently blogged about the issue and it appears to still be an issue in the Windows Server 2019 preview.

Just as Joey suggests, I always advise my customers to build out the nodes and any Storage Spaces BEFORE they start the clustering process. This makes the process go much smoother. It also allows the customer to have some time to benchmark the server’s performance before they add any replication, to  ensure everything is working as expected.

 

 

“Incomplete Communication with Cluster” with local Storage Space for SQL Server cluster

iCalc events still appearing on Wordpress Upcoming Events Widget even after deleted

I sync an iCal calendar feed to a WordPress site using the Upcoming Events Widget. I do this primarily because it is the only calendar widget available with the free version of WordPress this non-profit is using.

The issue I had is that I deleted an event last week, yet it still shows in my WordPress site through this sidebar widget. I would think it was a refresh issue, but edits to other events at the same time have already sync’d to the WordPress site.

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This event was deleted from my iCalc calendar, yet it still appears in my Upcoming Events Widget

I even tried deleting the Widget and adding a new one and the new widget also shows the events that I deleted.

I was beginning to get a bit frustrated and of course I had a band parents breathing down my neck questioning my ability to manage the band parent association website. Okay, not really, but they did point out the discrepancy on the calendar and I assumed that they just thought I was an idiot.

After a bit of Googling turned up nothing, it occurred to me that this was a reoccurring event. When I deleted that event, I simply delete that particular occurrence of the events, not the whole series of events.

Sure enough, after I deleted the whole series of recurring events the event disappeared from the Upcoming Events Sidebar widget about an hour later. Longs story short, the Upcoming Events Widget in WordPress does not handle exceptions to recurring events reliably.

iCalc events still appearing on Wordpress Upcoming Events Widget even after deleted