Re: persistent read cache

Thanks for the info. on bcache etc., first time heard about it. But it
seems quite coarse grained for the needs of a database.

The closest thing might be this implemented by the RocksDB engine:
https://github.com/facebook/rocksdb/wiki/Persistent-Read-Cache

On Mon, Feb 12, 2018 at 9:18 AM, Steve Atkins <steve(at)blighty(dot)com> wrote:
>
>> On Feb 11, 2018, at 5:14 PM, Sand Stone <sand(dot)m(dot)stone(at)gmail(dot)com> wrote:
>>
>>
>> Hi. I wonder if there is such a thing or extension in the PG world.
>>
>> Here is my use case. I am using PG (PG10 to be more specific) in a
>> cloud VM environment. The tables are stored in RAID0 managed SSD
>> backed attached storage. Depending on the VM I am using, I usually
>> have 256GB local SSD unused.
>>
>> I wonder if PG could leverage this local SSD as a read (page/block)
>> cache, to complement/extend the DRAM by used by shared_buffer today.
>
> It seems something that PostgreSQL could take advantage of, but
> it's probably the wrong layer to implement it. If your VM infrastructure
> doesn't have any way to use it directly, maybe you could do it at the
> drive / filesystem level with something like bcache, lvmcache or
> enhanceio?
>
> Adding that sort of complexity to something that needs solid data
> integrity makes me nervous, but those solutions have been in the
> field for years.
>
> Cheers,
> Steve
>
>
>