> On Nov 18, 2025, at 2:30 AM, Dongsheng Song <[email protected]> wrote:
>
> Hi,
>
> When Cassandra encountered data persistence failure (e.g., storage
> pauses/IO hanging, or full storage) for a short time, if we configured
> sufficient memory for Cassandra (e.g., Heap Memory, Direct Memory)
> and appropriately increase `memtable_heap_space` and
> `memtable_offheap_space`, so that Cassandra has enough memory to save
> the memtable even if flushing to SSTable fails, can Cassandra still
> provide services and perform data query or modification operations?
>
> Thanks,
> Dongsheng
What you are talking about will keep the memtable flush from happening, but you
are missing a key part of durability. The node has to write to the commit log
before acknowledging the write. If the write can’t happen, the node returns a
failure.
This is why replicas are an important part of the uptime feature of Cassandra.
If one node is having an intermittent issue, the cluster should work around the
troubled node and recover automatically.
Patrick
