[Gluster-devel] Data Classification: would it be possible to have a RAM-disk as caching tier?

[Niels de Vos]

On Mon, Feb 16, 2015 at 05:54:15AM -0500, Joseph Fernandes wrote:
> Hi Niels,
> 
> Well the idea is good, RAM-Disk would fastest and with no extra cost +
> We may have gluster brick from RAM-Disk[1]
> The one and the biggest challenge would be durability of data on RAM-Disks
> Using RAM for caching is good, as the cache will have only the copy of the original data
> but in case of tiering, the original data sits on the tier(not the copy).

Thanks for the swift resonse!

I imagine a solution where the hot contents are not moved to the
RAM-disk, but are replicated on demand. When the contents gets cold, the
replication can be reduced again, which would make space on the
RAM-disk. Upon boot, the RAM-disk would be empty, and only the
hot-contents would need to get 'healed' onto the RAM-disk. (The fastest
brick of a replica pair handles the reads, I assume that this would be
the RAM-disk.)

At the moment I can not say if the current data-classification proposal
is flexible enough to configure a policy like this. Or, how easy it
would be to extend the feature to allow configurations like this as an
improvement later on.

Cheers,
Niels


> 
> Dan your thoughts.
> 
> Thanks,
> Joe
> 
> 1. https://lists.gnu.org/archive/html/gluster-devel/2013-05/msg00118.html
> 
> ----- Original Message -----
> From: "Niels de Vos" <ndevos at redhat.com>
> To: gluster-devel at gluster.org
> Cc: "Dan Lambright" <dlambrig at redhat.com>, "Joseph Fernandes" <josferna at redhat.com>
> Sent: Monday, February 16, 2015 4:14:37 PM
> Subject: Data Classification: would it be possible to have a RAM-disk as caching tier?
> 
> Hi guys,
> 
> at FOSDEM one of our users spoke to me about their deployment and
> environment. It seems that they have a *very* good deal with their
> hardware vendor, which makes it possible to stuff their servers full
> with RAM for a minimal difference of the costs.
> 
> They expressed interest in having a RAM-disk as caching tier on the
> bricks. Would a configuration like this be possible with the
> data-classification feature [1]?
> 
> Thanks,
> Niels
> 
> 1. http://www.gluster.org/community/documentation/index.php/Features/data-classification