# Bcache\_cache\_errors **URL:** \ **Category:** Alerts\ **Created:** [November 1, 2021, 7:43am UTC](https://community.netdata.cloud/t/bcache-cache-errors/1892 "2021-11-01T07:43:09Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Ancairon](https://yyz1.discourse-cdn.com/flex029/user_avatar/community.netdata.cloud/ancairon/32/1001_2.png) [@Ancairon](https://community.netdata.cloud/u/Ancairon)\ **Post date:** [November 1, 2021, 7:43am UTC](https://community.netdata.cloud/t/bcache-cache-errors/1892/1 "2021-11-01T07:43:09Z")
# bcache\_cache\_errors ## OS: Any This alert presents the number of `bcache` read races in the last minute. The `bucket` was reused and invalidated while reading from the cache. When this occurs, the data is reread from the backing device. > `bcache` is a cache in the block layer of the Linux Kernel. **It allows fast storage devices** , as SSDs > (Solid State Drives), **to act as a cache for slower storage devices** , such as HDDs (Hard Disk Drives). As a result, **hybrid volumes are made with performance improvements**. Generally, a cache device is divided up into `buckets`, matching the physical disk’s erase blocks.[1](https://en.wikipedia.org/wiki/Bcache) [2](https://lwn.net/Articles/394672/) There is a mechanism where `bcache` can keep the cache disk full (typically your SSD), and when it needs to write more data, it selects a `bucket`, invalidates it, and removes all pointers from it. **The alert got triggered, because while there was a reading operation from the cache** _(meaning the data is stored inside a bucket)_ **that bucket got invalidated so the read operation couldn’t be completed.** Following up, the data is reread from the backing device (normally your HDD). > **References and Sources** > > [[1] Wikipedia](https://en.wikipedia.org/wiki/Bcache) > [[2] Bcache: Caching beyond just RAM](https://lwn.net/Articles/394672/) > [Kernel.org](https://www.kernel.org/doc/html/latest/admin-guide/bcache.html#) > [Bcache](https://wiki.archlinux.org/title/bcache)