any alternative solution for cache servers with hybrid disks（hdd/ssd）？

[wangchunpeng]

We are planning to use ATS as the cache engine for our CDN, and given servers with 10 hdd and 2 ssd disks. We want to store high-frequency access resources or some small files on the SSDs. Older versions of ATS supported specific features for this, but those features have been removed in latest versions. I would like to ask the reasons for this removal and whether there are any alternative solutions in recent versions？

[masaori335]

You can define volumes on your SSD by storage.config and use the volumes to specific hostname or domain by hosting.config.

• https://docs.trafficserver.apache.org/en/10.0.x/admin-guide/files/volume.config.en.html#exclusive-spans-and-volume-sizes
• https://docs.trafficserver.apache.org/en/10.0.x/admin-guide/files/hosting.config.en.html

This is described in the "Partitioning the Cache" section.

• https://docs.trafficserver.apache.org/en/10.0.x/admin-guide/storage/index.en.html#partitioning-the-cache

Older versions of ATS supported specific features for this, but those features have been removed in latest versions.

What was this feature called? do you have a link to the doc describe this?

[wangchunpeng]

You can define volumes on your SSD by storage.config and use the volumes to specific hostname or domain by hosting.config.

• https://docs.trafficserver.apache.org/en/10.0.x/admin-guide/files/volume.config.en.html#exclusive-spans-and-volume-sizes
• https://docs.trafficserver.apache.org/en/10.0.x/admin-guide/files/hosting.config.en.html

This is described in the "Partitioning the Cache" section.

• https://docs.trafficserver.apache.org/en/10.0.x/admin-guide/storage/index.en.html#partitioning-the-cache

Older versions of ATS supported specific features for this, but those features have been removed in latest versions.

What was this feature called? do you have a link to the doc describe this?

the interim caching feature ，https://cwiki.apache.org/confluence/display/TS/SSDSupport

[masaori335]

I know nothing about interim caching, but the old ticket removed the feature describe reasons and suggests below.

1. Assigning content to volumes and disks via our existing configs.
2. Use Linux’s bcache feature, which comes with Linux 3.10 or later. I suspect e.g. ZFS has something similar.
3. Use a third party system to implement the hybrid device (e.g. flash cache or EnhanceIO.

TS-3541 Eliminate interim cache

[masaori335]

Do you using hierarchy caching in your CDN? In general CDN deployment, using SSD on child layer and using HDD on parent layer makes sense for balance of cost efficiency and cache space.