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 HDMR BPMR with BPMR with SMR HAMR with SMR HAMR SMR (Heat Assisted Magnetic Recording) 1 BPMR SMR (Bit Patterned Magnetic Recording) PMR (Shingle Magnetic Recording) PMR (Perpendicular Magnetic Recording) 0.1 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 3 Data adapted from ASTC Technology Roadmap (http://www.idema.org/?page_id=5868)
Shingled Magnetic Recording (SMR) Forward-write only: Radial AND Rotational 4 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
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 Host Aware: No change: regular Requires new Regular SD drive SD drive device & FS FS benefits from Capacity gains like knowledge of media Drive Managed layout 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 Goals • Optimally Directed Writes – efficient • Forward-write only streams • CoW requirement • Excellent Reads – streaming • Zone aware (ZAC/ZBC) • File defragmentation • Boundaries • Metadata handling • New Commands • Backwards compatibility • REPORT_ZONES • • Provide reference design for other RESET_WRITE_POINTER file systems • OPEN/CLOSE/FINISH ZONE • New algorithms • Defragmentation 9
SMRFS -EXT4 • Default FS • Build upon of many strengths distros Popular FS Stability Compatible Market on-disk Acceptance format • Popular in • Minimal architecture commercial changes; only storage rearrangement of applications existing data 10
Proposed Stages EXT4 SMRFFS Project Scope Steps 1. cmd line arguments v1 Utilities v7 Enforce Host Managed 2. internal handling changes v2 Garbage Collection v5 v6 3. kernel stack changes v3 Kernel Integration v4 Specify mkfs Options for HA 4. IOCTL integrations v1 v4 v3 Kernel Stack v2 v2 v2 v2 EXT4 5. Algorithm enhancements v5 Internal SCSI changes 6. Utility updates v6 Disk 7. Host Managed Compliance v7 12
Proposed Stack Changes V3 - Kernel Stack Changes, V4 Kernel Integration VFS VFS Examine/Enforce I/O Ordering EXT4 √ Page Cache IOCTL √ I/O Scheduler O_Direct 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
File System Parameters Influence Performance For Drive Managed SMR Drive Managed SMR - Performance by FS Parameters, for different Workloads 200 180 Throughput - MB/s 160 140 120 driveA 100 driveB 80 driveC 60 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 Mimic OS Load Mimic DVD Download 5meg files Deep Dir 1meg files Deep Dir Re-arranging file system parameters for CoW to enforce forward-write- only improves performance of a DM-SMR-enabled system 15
Q&A Thank You! Attendees and Partners
Recommend
More recommend
