Date: Wed, 18 Nov 2015 12:13:09 -0500 From: "Kenneth D. Merry" <ken@FreeBSD.ORG> To: scsi@freebsd.org, current@freebsd.org Subject: CAM Shingled Disk support patches available Message-ID: <20151118171309.GA3564@mithlond.kdm.org>
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I have work in progress patches to add SMR (Shingled Magnetic Recording) support to CAM and GEOM here: FreeBSD/head as of SVN revision 290997: https://people.freebsd.org/~ken/cam_smr.head.20151117.1.txt FreeBSD stable/10 as of SVN revision 290995: https://people.freebsd.org/~ken/cam_smr.stable10.20151117.1.txt This includes support for Host Managed, Host Aware and Drive Managed SMR drives that are either SCSI (ZBC) or ATA (ZAC) attached via a SAS controller. This does not include support for SMR ATA drives attched via an ATA controller. Also, I have not yet figured out how to properly detect a Host Managed ATA drive, so this code won't do that. The big drive vendors are moving to SMR for at least some of their drives. The primary challenge with SMR is that it requires writing a relatively large zone sequentially starting at the beginning of the zone. The usual zone size is 256MB. It is conceptually almost like having a 256MB sector size. We (Spectra Logic) are working on ZFS changes that will use this CAM and GEOM infrastructure to make ZFS play well with SMR drives. Those changes aren't yet done. The patches linked above include: o A new 'camcontrol zone' command that allows displaying and managing drive zones via SCSI/ATA passthrough. o A new zonectl(8) utility that uses the new DIOCZONECMD ioctl to display and manage zones via the da(4) (and later ada(4)) driver. o Changes to diskinfo -v to display the zone mode of a drive. o A new disk zone API, sys/sys/disk_zone.h. o A new bio type, BIO_ZONE, and modifications to GEOM to support it. This new bio will allow filesystems to query zone support in a drive and manage zoned drives. o Extensive modifications to the da(4) driver to handle probing SCSI and SATA behind SAS SMR drives. o Additional CAM CDB building functions for zone commands. The current issues that need to be addressed are: o The da(4) driver now has 6 additional probe states, 5 of which are needed for probing ATA drives behind SAS controllers. I have not yet added support for BIO_ZONE bios to ada(4), but it will be very similar to the da(4) driver version. The ATA probe code needs to be pulled out of the da(4) driver and changed into a form that will allow it to work for either the ada(4) or da(4) driver. Otherwise we'll have a fair amount of code duplication between the two drivers. o There is a reasonable amount of code duplication between 'camcontrol zone' and zonectl(8). This was done for speed / expediency's sake, but it may be possible to make more of the code common there. o In order to add the new BIO_ZONE bio command, I had to change the bio_cmd field in struct bio from a uint8_t to a uint16_t. This will cause binary compatibility problems with any 3rd party loadable modules. Advice on how to handle this would be welcome. o In the process of developing these changes, I discovered that the dxfer_len paramter for scsi_ata_pass_16() was too small (uint16_t, and it needed to be uint32_t). I increased it, but that will potentially cause a binary incompatibility problem with any existing applications that use the current API via libcam. Advice on how to handle that would be welcome. If you look through the code, you'll notice that the disk_zone.h API is separate from the SCSI and ATA APIs. The intent is to allow filesystems and other consumers of the API to just talk to the disk zone API without dealing with the SCSI and ATA specifics. Another reason behind all of this is that even though the SCSI ZBC and ATA ZAC specs were developed in concert, and are intended to be functionally identical, they are still SCSI and ATA. As usual, SCSI is big endian and ATA is little endian. So to present a common API to the filesystem, we give all of the zone data back in native byte order, regardless of the underlying device protocol. Another thing to note is the extensive use of ATA passthrough in the da(4) driver. This is necessary because the SCSI SAT (SCSI to ATA Translation) specification has not yet caught up with translating SCSI zone commands (ZBC) to ATA zone commands (ZAC). So, until the spec is updated and LSI and other vendors update their SCSI to ATA translation layers, we'll have to use the ATA version of the commands when talking to ATA drives via SAS controllers. I have only tested the code so far with Seagate SATA Drive Managed and Host Aware drives. I would appreciate testing with any drives. (And testing to make sure that the patches don't cause problems with existing hardware.) Right now, all you can really do is manage the zones manually using camcontrol(8) or zonectl(8). Automatic management will come with the ZFS changes. (Or changes to other filesysems if people want to do it.) If you have a SATA Host Aware drive, in theory camcontrol(8) should allow you to manage the drive if you have it attached to a SATA controller. Here is an example of some of the commands. Get general zoning information: [root@sm4u-1 ~]# zonectl -c params -d /dev/da21 Zone Mode: Host Aware Command support: Report Zones, Open, Close, Finish, Reset Write Pointer Unrestricted Read in Sequential Write Required Zone (URSWRZ): No Optimal Number of Open Sequential Write Preferred Zones: 128 Optimal Number of Non-Sequentially Written Sequential Write Preferred Zones: 8 Maximum Number of Open Sequential Write Required Zones: Unlimited Look at information from the da(4) driver: [root@sm4u-1 ~]# sysctl kern.cam.da.21 kern.cam.da.21.delete_method: NONE kern.cam.da.21.delete_max: 1081344 kern.cam.da.21.minimum_cmd_size: 6 kern.cam.da.21.sort_io_queue: -1 kern.cam.da.21.zone_mode: Host Aware kern.cam.da.21.zone_support: Report Zones, Open, Close, Finish, Reset Write Pointer kern.cam.da.21.optimal_seq_zones: 128 kern.cam.da.21.optimal_nonseq_zones: 8 kern.cam.da.21.max_seq_zones: 4294967295 kern.cam.da.21.error_inject: 0 Display all of the zones with zonectl(8): [root@sm4u-1 ~]# zonectl -d /dev/da21 -c rz 29809 zones, Maximum LBA 0x3a3812aaf (15628053167) Zone lengths and types may vary Start LBA Length WP LBA Zone Type Condition Sequential Reset 0, 524288, 0x80000, Conventional, NWP, Sequential, No Reset Needed 0x80000, 524288, 0x100000, Conventional, NWP, Sequential, No Reset Needed 0x100000, 524288, 0x180000, Conventional, NWP, Sequential, No Reset Needed 0x180000, 524288, 0x200000, Conventional, NWP, Sequential, No Reset Needed 0x200000, 524288, 0x280000, Conventional, NWP, Sequential, No Reset Needed 0x280000, 524288, 0x300000, Conventional, NWP, Sequential, No Reset Needed 0x300000, 524288, 0x380000, Conventional, NWP, Sequential, No Reset Needed 0x380000, 524288, 0x400000, Conventional, NWP, Sequential, No Reset Needed 0x400000, 524288, 0x480000, Conventional, NWP, Sequential, No Reset Needed 0x480000, 524288, 0x500000, Conventional, NWP, Sequential, No Reset Needed 0x500000, 524288, 0x580000, Conventional, NWP, Sequential, No Reset Needed 0x580000, 524288, 0x600000, Conventional, NWP, Sequential, No Reset Needed 0x600000, 524288, 0x680000, Conventional, NWP, Sequential, No Reset Needed 0x680000, 524288, 0x700000, Conventional, NWP, Sequential, No Reset Needed 0x700000, 524288, 0x780000, Conventional, NWP, Sequential, No Reset Needed [ ... ] 0x1f00000, 524288, 0x1f80000, Conventional, NWP, Sequential, No Reset Needed 0x1f80000, 524288, 0x2000000, Conventional, NWP, Sequential, No Reset Needed 0x2000000, 524288, 0x2080000, Seq Preferred, Full, Sequential, No Reset Needed 0x2080000, 524288, 0x2100000, Seq Preferred, Full, Sequential, No Reset Needed 0x2100000, 524288, 0x2180000, Seq Preferred, Full, Sequential, No Reset Needed 0x2180000, 524288, 0x2200000, Seq Preferred, Full, Sequential, No Reset Needed 0x2200000, 524288, 0x2280000, Seq Preferred, Full, Sequential, No Reset Needed 0x2280000, 524288, 0x2300000, Seq Preferred, Full, Sequential, No Reset Needed [ ... ] Use camcontrol zone to reset the write pointer for the first shingled zone listed above: [root@sm4u-1 ~]# camcontrol zone da21 -v -c rwp -l 0x2000000 Use camcontrol zone to ask the drive to report empty zones: [root@sm4u-1 ~]# camcontrol zone da21 -v -c rz -o empty 1 zones, Maximum LBA 0x3a3812aaf (15628053167) Zone lengths and types may vary Start LBA Length WP LBA Zone Type Condition Sequential Reset 0x2000000, 524288, 0x2000000, Seq Preferred, Empty, Sequential, No Reset Needed Get information on a Host Aware drive: root@sm4u-1 ~]# diskinfo -v da21 da21 512 # sectorsize 8001563222016 # mediasize in bytes (7.3T) 15628053168 # mediasize in sectors 4096 # stripesize 0 # stripeoffset 972801 # Cylinders according to firmware. 255 # Heads according to firmware. 63 # Sectors according to firmware. Z84008NY # Disk ident. enc@5003048001f311fd/elmtype@array_device/slot@22 # Physical path Host Aware # Zone Mode Get information on a drive managed drive: [root@sm4u-1 ~]# diskinfo -v da20 da20 512 # sectorsize 8001563222016 # mediasize in bytes (7.3T) 15628053168 # mediasize in sectors 4096 # stripesize 0 # stripeoffset 972801 # Cylinders according to firmware. 255 # Heads according to firmware. 63 # Sectors according to firmware. Z8405938 # Disk ident. enc@5003048001f311fd/elmtype@array_device/slot@21 # Physical path Drive Managed # Zone Mode Get information on a non-zoned drive: [root@sm4u-1 ~]# diskinfo -v da4 da4 512 # sectorsize 100030242816 # mediasize in bytes (93G) 195371568 # mediasize in sectors 0 # stripesize 0 # stripeoffset 12161 # Cylinders according to firmware. 255 # Heads according to firmware. 63 # Sectors according to firmware. 124903574F36 # Disk ident. enc@5003048001f311fd/elmtype@array_device/slot@5 # Physical path Not Zoned # Zone Mode Testing and comments are welcome. Thanks, Ken -- Kenneth Merry ken@FreeBSD.ORG
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