I am not talking about cache. The main issue for me with cache is at the beginning the first block is searched through the slow disk, then put in cache.

I want often read blocks to be definitively on faster disks if there is some and stay on it. And consequently move less often read blocks from fast storage to slower ones.

So it looks to me that zfs has this feature, but I am not sure on the name it deserves if I want to compare to other kinds of filesystem like Btrfs or Ceph, or other kind of storage. It looks like Adaptive replacement cache but without the cache part.

Professional storage solutions like HPE 3PAR or EMC Avamar have such features, like adaptive optimization but they give it some special proprietary name, and I can not use these names to compare with open source solutions.

How would you name such a feature?

  • edit : thanks to slm to direct me to RPAC : regional popularity-aware cache, it drive me then to Automated tiered storage
  • All the various characteristics for filesystems are listed here in wikipedia - en.wikipedia.org/wiki/Comparison_of_file_systems.
    – slm
    Sep 6 '18 at 5:33
  • "The management of disk space by using SSDs for caching and tiering has been extensively studied. The twin goals of reducing the copying of blocks while making residual HDD accesses as spatially coherent as possible can be met by the RPAC replacement policy [33] in which ‘chunks’ of data are moved between disks on the basis of their popularity" - ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7506304
    – slm
    Sep 6 '18 at 5:36
  • 1
    The above sounds like exactly what you're describing, no?
    – slm
    Sep 6 '18 at 5:36
  • There's also dm-cache - redhat.com/en/blog/improving-read-performance-dm-cache.
    – slm
    Sep 6 '18 at 5:41
  • thanks @slm, yes it does sound like what I search. But it still not easy to search for filesystem or block storage technology that have this capability.
    – dominix
    Sep 6 '18 at 19:58

to my point of view it looks to be automated tiered storage

However there is a lot of sub-nomination around, I have met EMC FAST Fully Automated Storage Tiering HPE Adaptive Optimization or even HSM Hierarchical storage management. So it is not easy to search on all filesystem capabilities to sort which are these with such features.

If you have tips that indicates which Of Ceph, ZFS, Brtfs, BeeGFS, RedHat GLuster Storage, of any other can do regarding automated tiered storage you welcome to indicate it to me.

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