Re: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device
Hi Jim, On Fri, Feb 07, 2014 at 05:32:44PM +, Jim Malina wrote: -Original Message- From: Hannes Reinecke [mailto:h...@suse.de] Sent: Friday, February 07, 2014 5:46 AM To: Carlos Maiolino; Albert Chen Cc: lsf...@lists.linux-foundation.org; James Borden; Jim Malina; Curtis Stevens; linux-...@vger.kernel.org; linux-fsde...@vger.kernel.org; linux- s...@vger.kernel.org Subject: Re: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device On 02/07/2014 02:00 PM, Carlos Maiolino wrote: Hi, On Sat, Feb 01, 2014 at 02:24:33AM +, Albert Chen wrote: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device Shingle Magnetic Recording is a disruptive technology that delivers the next areal density gain for the HDD industry by partially overlapping tracks. Shingling requires physical writes to be sequential, and opens the question of how to address this behavior at a system level. Two general approaches contemplated are to either to do the block management in the device or in the host storage stack/file system through Zone Block Commands (ZBC). The use of ZBC to handle SMR block management yields several benefits such as: - Predictable performance and latency - Faster development time - Access to application and system level semantic information - Scalability / Fewer Drive Resources - Higher reliability Essential to a host managed approach (ZBC) is the openness of Linux and its community is a good place for WD to validate and seek feedback for our thinking - where in the Linux system stack is the best place to add ZBC handling? at the Device Mapper layer? or somewhere else in the storage stack? New ideas and comments are appreciated. If you add ZBC handling into the device-mapper layer, aren't you supposing that all SMR devices will be managed by device-mapper? This doesn't look right IMHO. These devices should be able to be managed via DM or either directly via de storage layer. And any other layers making use of these devices (like DM for example) should be able to communicate with them and send ZBC commands as needed. Clarification: ZBC is an interface protocol. A new device and command set. SMR is a recording technology. You may have ZBC without SMR or SMR without ZBC. For examples. SSD may benefit from ZBC protocol to improve performance and reduce wear. SMR may be 100% device managed and not provide information required of a ZBC device, like write pointers or zone boundaries. Thanks for clarification, and, this just enforce my concept that ZBC protocol should be integrated in the generic block layer not make it device-mapper dependent. So, make this available to any device that supports it with or without the help of DM. Precisely. Adding a new device type (and a new ULD to the SCSI midlayer) seems to be the right idea here. Then we could think of how to integrate this into the block layer; eg we could identify the zones with partitions, or mirror the zones via block_limits. There is actually a good chance that we can tweak btrfs to run unmodified on such a disk; after all, sequential writes are not a big deal for btrfs. The only issue we might have is that we might need to re-allocate blocks to free up zones. But some btrfs developers have assured me this shouldn't be too hard. Personally I don't like the idea of _having_ to use a device-mapper module for these things. What I would like is giving the user a choice; if there are specialized fs around which can deal with such a disk (hello, ltfs :-) then fine. If not of course we should be having a device-mapper module to hide the grubby details for unsuspecting filesystems. Cheers, Hannes -- Dr. Hannes Reinecke zSeries Storage h...@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg) jim -- To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- Carlos -- To unsubscribe from this list: send the line unsubscribe linux-scsi in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device
Hi, On Sat, Feb 01, 2014 at 02:24:33AM +, Albert Chen wrote: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device Shingle Magnetic Recording is a disruptive technology that delivers the next areal density gain for the HDD industry by partially overlapping tracks. Shingling requires physical writes to be sequential, and opens the question of how to address this behavior at a system level. Two general approaches contemplated are to either to do the block management in the device or in the host storage stack/file system through Zone Block Commands (ZBC). The use of ZBC to handle SMR block management yields several benefits such as: - Predictable performance and latency - Faster development time - Access to application and system level semantic information - Scalability / Fewer Drive Resources - Higher reliability Essential to a host managed approach (ZBC) is the openness of Linux and its community is a good place for WD to validate and seek feedback for our thinking - where in the Linux system stack is the best place to add ZBC handling? at the Device Mapper layer? or somewhere else in the storage stack? New ideas and comments are appreciated. If you add ZBC handling into the device-mapper layer, aren't you supposing that all SMR devices will be managed by device-mapper? This doesn't look right IMHO. These devices should be able to be managed via DM or either directly via de storage layer. And any other layers making use of these devices (like DM for example) should be able to communicate with them and send ZBC commands as needed. For more information about ZBC, please refer to Ted's ty...@mit.edu email to linux-fsde...@vger.kernel.org with the subject [RFC] Draft Linux kernel interfaces for ZBC drives. -- To unsubscribe from this list: send the line unsubscribe linux-fsdevel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- Carlos -- To unsubscribe from this list: send the line unsubscribe linux-scsi in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device
On 02/07/2014 02:00 PM, Carlos Maiolino wrote: Hi, On Sat, Feb 01, 2014 at 02:24:33AM +, Albert Chen wrote: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device Shingle Magnetic Recording is a disruptive technology that delivers the next areal density gain for the HDD industry by partially overlapping tracks. Shingling requires physical writes to be sequential, and opens the question of how to address this behavior at a system level. Two general approaches contemplated are to either to do the block management in the device or in the host storage stack/file system through Zone Block Commands (ZBC). The use of ZBC to handle SMR block management yields several benefits such as: - Predictable performance and latency - Faster development time - Access to application and system level semantic information - Scalability / Fewer Drive Resources - Higher reliability Essential to a host managed approach (ZBC) is the openness of Linux and its community is a good place for WD to validate and seek feedback for our thinking - where in the Linux system stack is the best place to add ZBC handling? at the Device Mapper layer? or somewhere else in the storage stack? New ideas and comments are appreciated. If you add ZBC handling into the device-mapper layer, aren't you supposing that all SMR devices will be managed by device-mapper? This doesn't look right IMHO. These devices should be able to be managed via DM or either directly via de storage layer. And any other layers making use of these devices (like DM for example) should be able to communicate with them and send ZBC commands as needed. Precisely. Adding a new device type (and a new ULD to the SCSI midlayer) seems to be the right idea here. Then we could think of how to integrate this into the block layer; eg we could identify the zones with partitions, or mirror the zones via block_limits. There is actually a good chance that we can tweak btrfs to run unmodified on such a disk; after all, sequential writes are not a big deal for btrfs. The only issue we might have is that we might need to re-allocate blocks to free up zones. But some btrfs developers have assured me this shouldn't be too hard. Personally I don't like the idea of _having_ to use a device-mapper module for these things. What I would like is giving the user a choice; if there are specialized fs around which can deal with such a disk (hello, ltfs :-) then fine. If not of course we should be having a device-mapper module to hide the grubby details for unsuspecting filesystems. Cheers, Hannes -- Dr. Hannes Reinecke zSeries Storage h...@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg) -- To unsubscribe from this list: send the line unsubscribe linux-scsi in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device
-Original Message- From: Hannes Reinecke [mailto:h...@suse.de] Sent: Friday, February 07, 2014 5:46 AM To: Carlos Maiolino; Albert Chen Cc: lsf...@lists.linux-foundation.org; James Borden; Jim Malina; Curtis Stevens; linux-...@vger.kernel.org; linux-fsde...@vger.kernel.org; linux- s...@vger.kernel.org Subject: Re: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device On 02/07/2014 02:00 PM, Carlos Maiolino wrote: Hi, On Sat, Feb 01, 2014 at 02:24:33AM +, Albert Chen wrote: [LSF/MM TOPIC] SMR: Disrupting recording technology meriting a new class of storage device Shingle Magnetic Recording is a disruptive technology that delivers the next areal density gain for the HDD industry by partially overlapping tracks. Shingling requires physical writes to be sequential, and opens the question of how to address this behavior at a system level. Two general approaches contemplated are to either to do the block management in the device or in the host storage stack/file system through Zone Block Commands (ZBC). The use of ZBC to handle SMR block management yields several benefits such as: - Predictable performance and latency - Faster development time - Access to application and system level semantic information - Scalability / Fewer Drive Resources - Higher reliability Essential to a host managed approach (ZBC) is the openness of Linux and its community is a good place for WD to validate and seek feedback for our thinking - where in the Linux system stack is the best place to add ZBC handling? at the Device Mapper layer? or somewhere else in the storage stack? New ideas and comments are appreciated. If you add ZBC handling into the device-mapper layer, aren't you supposing that all SMR devices will be managed by device-mapper? This doesn't look right IMHO. These devices should be able to be managed via DM or either directly via de storage layer. And any other layers making use of these devices (like DM for example) should be able to communicate with them and send ZBC commands as needed. Clarification: ZBC is an interface protocol. A new device and command set. SMR is a recording technology. You may have ZBC without SMR or SMR without ZBC. For examples. SSD may benefit from ZBC protocol to improve performance and reduce wear. SMR may be 100% device managed and not provide information required of a ZBC device, like write pointers or zone boundaries. Precisely. Adding a new device type (and a new ULD to the SCSI midlayer) seems to be the right idea here. Then we could think of how to integrate this into the block layer; eg we could identify the zones with partitions, or mirror the zones via block_limits. There is actually a good chance that we can tweak btrfs to run unmodified on such a disk; after all, sequential writes are not a big deal for btrfs. The only issue we might have is that we might need to re-allocate blocks to free up zones. But some btrfs developers have assured me this shouldn't be too hard. Personally I don't like the idea of _having_ to use a device-mapper module for these things. What I would like is giving the user a choice; if there are specialized fs around which can deal with such a disk (hello, ltfs :-) then fine. If not of course we should be having a device-mapper module to hide the grubby details for unsuspecting filesystems. Cheers, Hannes -- Dr. Hannes Reinecke zSeries Storage h...@suse.de+49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg) jim -- To unsubscribe from this list: send the line unsubscribe linux-scsi in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
