SMR in Linux Systems Seagate's Contribution to Legacy File Systems Adrian Palmer, Drive Development Engineering
SEAGATE combines DIFFERENT TECHNOLOGIES in new ways to SOLVE customer data storage CHALLENGES 2
Shingled Magnetic Recording (SMR) Areal density growth curve lowest cost/gb 10 TB/in^2 HAMR with SMR BPMR with SMR HDMR with BPMR 1 PMR SMR SMR (Shingle Magnetic Recording) HAMR (Heat Assisted Magnetic Recording) BPMR (Bit Patterned Magnetic Recording) 0.1 PMR (Perpendicular Magnetic Recording) 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 Data adapted from ASTC Technology Roadmap (http://www.idema.org/?page_id=5868) 3
Shingled Magnetic Recording (SMR) Forward-write only: Radial AND Rotational Image: Wood, R.; Williams, Mason; Kavcic, A.; Miles, Jim, "The Feasibility of Magnetic Recording at 10 Terabits Per Square Inch on Conventional Media," Magnetics, IEEE Transactions on, vol.45, no.2, pp.917,923, Feb. 2009 4
SMR Drive Types Drive Managed (DM) Mimics Traditional drives Backwards compatible Direct Replacement for conventional drives in conventional apps Host Managed (HM) Not backwards compatible Host required to manage data ordering for performance mitigation Extensions required in ATA and SCSI command sets Host Aware (HA) Combination of DM and HM. Backwards compatible / Able to use extensions in ATA and SCSI
Drive Managed Compatibility for Today Host Aware Performance for Tomorrow Drive Managed Host Managed Host Aware No change: regular SD drive Requires new device & FS Regular SD drive FS benefits from knowledge of media layout Host Aware: Capacity gains like Drive Managed Performance like Conventional 6
SMR Can we avoid it? Benefits Provides continued growth in Areal Density. Enables lower cost/gb disc drives Base of new technologies HAMR Support Readiness ZBC/ZAC specifications are nearing completion T10/T13 committees work actively progressing Availability Millions of DM drives shipped! Seagate s 8TB Archive HDD v2 drive is SMR DM in production, HA forthcoming ZBC: Zoned Block Commands ZAC: Zoned device ATA Commands
ZAC/ZBC Standards Inspired by SMR. Applicable to any media Separates media into bounded zones Write Pointer Zones Sequential write only for Host Managed (restrictive) Sequential write preferred for Host Aware (permissive) New common ATA/SCSI commands REPORT ZONES RESET WRITE POINTER OPEN/CLOSE/FINISH ZONE Requires communication with FS beyond simple Read/Write 8
SMR Friendly File System Requirements Forward-write only CoW requirement Zone aware (ZAC/ZBC) Boundaries New Commands REPORT_ZONES RESET_WRITE_POINTER OPEN/CLOSE/FINISH ZONE New algorithms Defragmentation Goals Optimally Directed Writes efficient streams Excellent Reads streaming File defragmentation Metadata handling Backwards compatibility Provide reference design for other file systems 9
SMRFS -EXT4 Default FS of many distros Build upon strengths Popular FS Stability Market Acceptance Compatible on-disk format Popular in commercial storage applications Minimal architecture changes; only rearrangement of existing data 10
Proposed Stages EXT4 SMRFFS Project Scope Steps v7 Enforce Host Managed v5 v4 Garbage Collection Kernel Integration Utilities v6 1. cmd line arguments v1 2. internal handling changes v2 3. kernel stack changes v3 v2 Internal changes v1 v2 Specify mkfs Options for HA v2 EXT4 SCSI Disk v2 Kernel Stack v3 4. IOCTL integrations v4 5. Algorithm enhancements v5 6. Utility updates v6 7. Host Managed Compliance v7 12
Proposed Stack Changes V3 - Kernel Stack Changes, V4 Kernel Integration VFS VFS EXT4 Examine/Enforce I/O Ordering O_Direct IOCTL Page Cache I/O Scheduler SCSI S-A-T ATA AHCI Disk 13
State of project We ve done Laid out design, made prototypes Discussion at LSF Consensus of key developers We ve got to do A lot of work in a short time And we need community help! Ask how to contribute and how to get sample drives at our booth! Contact us after Vault at adrian.palmer@seagate.com or timothy.r.feldman@seagate.com Seagate Confidential 14
ext4 ext4 flex_bg ext4 dm-cow zfs btrfs ext4 ext4 flex_bg ext4 dm-cow zfs btrfs ext4 ext4 flex_bg ext4 dm-cow zfs btrfs ext4 ext4 flex_bg ext4 dm-cow zfs btrfs Throughput - MB/s File System Parameters Influence Performance For Drive Managed SMR 200 180 160 140 120 100 80 60 Drive Managed SMR - Performance by FS Parameters, for different Workloads drivea driveb drivec Mimic OS Load Mimic DVD Download 5meg files Deep Dir 1meg files Deep Dir Re-arranging file system parameters for CoW to enforce forward-writeonly improves performance of a DM-SMR-enabled system 15
Q&A Thank You! Attendees and Partners