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Tiered storage has been done before, this is true. However, they are dedicated systems. If "Fusion Drive" is at the OS level, that means it shares resources wit

Tiered storage has been done before, this is true. However, they are dedicated systems. If "Fusion Drive" is at the OS level, that means it shares resources with the rest of the system which presents more/different challenges.

vubuntu 14y ago
StorSimple implements auto-tiering at block level and presents an iscsi target block device transparently to the OS/Filesystem layer. It is built on top of already available open source linux iscsi target software. If Fusion was done in similar manner, it absolutely does not require any modifications to the regular OS/file system layers at all. The intelligent auto-tiering capable iSCSI target portion would be at the driver level well isolated from the rest of the OS/filesystem components. It probably even has more simplistic rules for tiering . Keep OS files/dir always on SSD. Apply tiering logic to app data using a simplistic LRU scheme. And there is only two tiers to deal with. I am no expert in Linux/iSCSI or auto-tiering, but I bet you this is something that a HP/3PAR or Dell Compellent can spin up at a very short notice using their existing technologies. Apple is very good at identifying a complex ( and in most cases an existing but end-user un-friendly) technology that has been under-utilized in consumer space and bring it down to consumer level and deliver it in a consumer-friendly manner and put a wonderful marketing spin on it with cool terminology (Retina display, Fusion drive)and possibly even patent some arcane & obvious variations of the main theme.
- cokernel_hacker 14y ago
  StorSimple, 3PAR, etc. all appear to be appliances. What I am trying to get as is subtle so I will try to be a little bit more explicit. StorSimple can dominate the appliance it is made out of to provide its services. Fusion Drive cannot dominate the owner's machine.
  - vubuntu 14y ago
    This might be oversimplifying a bit - How about keeping all OS files, app files etc on SSD. No auto-tiering of those. - Then some equivalent of a 'cron job + filter driver' combo that moves data files to and from SSD to the 1/3TB disk? When I say filter driver, I am thinking of Windows file system mini-filter driver. Linux equivalent would be VFS I guess. How difficult is it to implement some thing like that in a pre known 2 tier configuration context? And what would be the effectiveness of such a solution? In Windows filter drivers have been used effectively to implement file tombstoning for archive purposes and utilizing reparse points/extended attributes to store the remote URI (for recalling file contents from remote archive upon intercepting a read request). It's not too hard to write a mini filter driver in Windows and use it in conjunction with reparse points to implement tombstoning in filesystem.
    - cokernel_hacker 14y ago
      Mini-filters are FS level as are VFS solutions. How do you tell a thing that sits at the VFS level about multiple devices? You could probably do it, nothing storage engineers solve is unsolvable :) It certainly seems unnatural. Most of those appliance solutions (and probably Fusion Drive for that matter) implement their mojo at the block level and provide block device interfaces. This is to aid their seamlessness, it makes them a lot more straightforward to implement and it makes them a lot more flexible. I would have trouble believing it would be simpler to implement it at a mini-filter/VFS level.

vubuntu 14y ago

StorSimple implements auto-tiering at block level and presents an iscsi target block device transparently to the OS/Filesystem layer. It is built on top of already available open source linux iscsi target software. If Fusion was done in similar manner, it absolutely does not require any modifications to the regular OS/file system layers at all. The intelligent auto-tiering capable iSCSI target portion would be at the driver level well isolated from the rest of the OS/filesystem components. It probably even has more simplistic rules for tiering . Keep OS files/dir always on SSD. Apply tiering logic to app data using a simplistic LRU scheme. And there is only two tiers to deal with. I am no expert in Linux/iSCSI or auto-tiering, but I bet you this is something that a HP/3PAR or Dell Compellent can spin up at a very short notice using their existing technologies. Apple is very good at identifying a complex ( and in most cases an existing but end-user un-friendly) technology that has been under-utilized in consumer space and bring it down to consumer level and deliver it in a consumer-friendly manner and put a wonderful marketing spin on it with cool terminology (Retina display, Fusion drive)and possibly even patent some arcane & obvious variations of the main theme.

cokernel_hacker 14y ago
StorSimple, 3PAR, etc. all appear to be appliances. What I am trying to get as is subtle so I will try to be a little bit more explicit. StorSimple can dominate the appliance it is made out of to provide its services. Fusion Drive cannot dominate the owner's machine.
- vubuntu 14y ago
  This might be oversimplifying a bit - How about keeping all OS files, app files etc on SSD. No auto-tiering of those. - Then some equivalent of a 'cron job + filter driver' combo that moves data files to and from SSD to the 1/3TB disk? When I say filter driver, I am thinking of Windows file system mini-filter driver. Linux equivalent would be VFS I guess. How difficult is it to implement some thing like that in a pre known 2 tier configuration context? And what would be the effectiveness of such a solution? In Windows filter drivers have been used effectively to implement file tombstoning for archive purposes and utilizing reparse points/extended attributes to store the remote URI (for recalling file contents from remote archive upon intercepting a read request). It's not too hard to write a mini filter driver in Windows and use it in conjunction with reparse points to implement tombstoning in filesystem.
  - cokernel_hacker 14y ago
    Mini-filters are FS level as are VFS solutions. How do you tell a thing that sits at the VFS level about multiple devices? You could probably do it, nothing storage engineers solve is unsolvable :) It certainly seems unnatural. Most of those appliance solutions (and probably Fusion Drive for that matter) implement their mojo at the block level and provide block device interfaces. This is to aid their seamlessness, it makes them a lot more straightforward to implement and it makes them a lot more flexible. I would have trouble believing it would be simpler to implement it at a mini-filter/VFS level.