Storage Queues demystify


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Before we go into the different sorts of queues, let’s first define “queue.”

Every Saturday, I go to the store to get my weekly groceries. The supermarket is crowded because it is the weekend. Adding items to my cart is simple, but invoicing is the most difficult aspect. At the billing counter, the cashier may only serve one customer at a time. Others will have to wait. Because billing is a time-consuming procedure. Many clients wait in line in front of the counter. As you may be aware, that line is referred to as a “Queue.”

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When IOs are waiting for storage to process them, they form a queue. There are numerous levels at which IOs are queued.


There are many reasons for IO queuing. Let’s discuss prominent causes.

Block size Mismatch

Input/Output (IO) block size mismatch can be one of the reasons for IO queuing. IO block size is the amount of data that is transferred in a single IO operation. If the IO block size requested by an application is different from the physical block size of the storage device, it can result in IO queuing. This happens because the storage device has to read or write more blocks to fulfill the IO request, which can lead to an increase in the IO queue length.

For example, if an application requests an IO operation with a block size of 4KB, but the storage device has a physical block size of 8KB, the device has to read or write two blocks to fulfill the request. This results in an increased number of IO operations, which can cause IO queuing.

Overwhelming workload

Overwhelming workload can be a reason for Input/Output (IO) queueing. IO queueing occurs when the rate at which data is produced exceeds the rate at which it can be processed. This can cause a backlog of data to accumulate, resulting in longer processing times and delays. In the context of computer systems, an overwhelming workload can cause IO queueing when the system is unable to handle the volume of input/output requests, leading to queueing of data waiting to be processed. This can affect the performance of the system and lead to slower response times.

Slow Storage

A slow SAN storage can cause IO (Input/Output) queueing, which means there is a delay in processing input/output requests, leading to a queue of pending requests. This can happen due to various reasons such as outdated hardware, outdated software, or overutilization of the SAN storage.

Slow SAN storage can cause IO queueing because the storage device takes longer to read or write data, which slows down the entire process. This can result in delays, slowdowns, and even crashes. IO queueing can be minimized by upgrading the hardware or software, reducing the workload on the storage device, or implementing load balancing techniques to distribute the workload evenly across multiple devices.

Remediate IO queueing

  1. Upgrade hardware: If your system is struggling to handle the workload, upgrading your hardware can help. You can upgrade your CPU, RAM, or add more storage to your computer.
  2. Optimize software: You can optimize the software running on your system to reduce the number of IO requests. This can include closing unnecessary applications, deleting unnecessary files, or using a disk defragmenter.
  3. Use a caching system: Caching can help reduce the number of IO requests by storing frequently accessed data in memory. This can speed up the performance of your system.
  4. Use a load balancer: If you have a high-traffic website, using a load balancer can help distribute the IO requests across multiple servers. This can help prevent IO queueing and improve the overall performance of your website.
  5. Use a solid-state drive: Solid-state drives (SSDs) are faster than traditional hard drives and can help reduce IO queueing. By using an SSD, you can speed up the performance of your system and reduce the number of IO requests.
  6. Use application and storage device with the same block size: It is recommended to configure the application and storage device with the same block size. This can help to reduce the IO queue length and improve the IO performance of the system.


IO queueing can significantly impact system performance, and it is essential to remediate it to ensure optimal system operation. Regular system maintenance, hardware upgrades, and optimizing software can help mitigate IO queueing issues.

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