Wojciech Malikowski (NVM Solutions Group) · 2019-04-29 · • SDPK FTL provides block device...

Wojciech Malikowski (NVM Solutions Group)

SPDK, PMDK & VTune™ Amplifier Summit

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SPDK, PMDK & VTune™ Amplifier Summit

Agenda

• Flash Translation Layer (FTL)overview

• Example use cases

• Write buffer cache for 4K PLI

• Zoned namespace

3

SPDK, PMDK & VTune™ Amplifier Summit 4

WHY DO WE NEED FTL• Standard SSD provides Flash

Translation Layer inside firmware

HOST

Flash Translation Layer:Data PlacementIO Scheduling

Garbage Collection

Media Handling

READ/WRITE Logical Block

READ/WRITE/ERASE

NANDDIE

STANDARD SSD

NANDDIE

NANDDIE

NANDDIE


WHY DO WE NEED FTL• Standard SSD provides Flash

Translation Layer inside firmware

• SDPK FTL provides block device access on top of non block SSD device implementing Open Channel interface

• Open Channel allows to control NAND flash data placement directly

• FTL logic should be moved from SSD firmware to the host

HOST


Garbage Collection

Media Handling

READ/WRITE Logical Block

READ/WRITE/ERASE

NANDDIE

STANDARD SSD

NANDDIE

NANDDIE

NANDDIE

HOST

Media Handling

READ/WRITE/ERASE Physical Page

READ/WRITE/ERASE

OPEN CHANNEL SSD


Garbage Collection

NANDDIE

NANDDIE

NANDDIE

NANDDIE


FTL OVERVIEW: core components/CONCEPTS• Geometry

• L2P table

• Write buffer

• Metadata

• Relocation module

• Abstracted NAND management (ANM)


FTL OVERVIEW: GEOMETRY• GROUP

• PU – parallel unit

• CHUNK

• LOGICAL BLOCK CHUNK (tens of MB)

LOGICAL BLOCK (4K)

MEDIA CONTROLLER

PU 1 (tens of GB)

PU 2 PU 3 PU 1 PU 2 PU 3

GROUP 1 GROUP 2

READ/WRITE/ERASE PHYSICAL ADDRESS

Open Channel SSD


FTL OVERVIEW: BaND• Band - collection of chunks,

each belongs to a different parallel unit

• FTL write pointer iterates over the chunks in band to achieve maximum write parallelism

• Band could be in open, close or free state

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CKH1

CHK2

CHKN

MEDIA CONTROLLER

PU 1 PU 2 PU 3 PU 1 PU 2 PU 3

GROUP 1 GROUP 2


Open Channel SSD

BAND 0

BAND 1

BAND 2

BAND N


FTL OVERVIEW: L2p tableLBA GROUP PU CHUNK BLOCK

0 0 1 8 0

4K 2 0 1 3

8K 2 1 3 5

…

• Maps logical address to physical address on disk

• Allocated in DRAM


FTL OVERVIEW: METADATA• We need to store metadata in

each band for restoring device and defragmentation process

• When band is opening, head metadata is written and when band becomes full, we write tail metadata

• Head metadata contains:device UUID, sequence number, version etc.

• Tail metadata contains LBA map for its band and its validity

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CKH1

CHK2

CHKN


BAND 0

BAND 1

BAND 2

BAND N


FTL OVERVIEW: METADATA• We need to store metadata in

each band for restoring device and defragmentation process

• When band is opening, head metadata is written and when band becomes full, we write tail metadata

• Head metadata contains:device UUID, sequence number, version etc.

• Tail metadata contains LBA map for its band and its validity

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CHK1

CHK2

CHKN

CHK0

CKH1

CHK2

CHKN


BAND 0

BAND 1

BAND 2

BAND N

BAND

CHUNK 1 CHUNK 2 CHUNK N

HEAD META

TAIL META

VALID MAP

Physical to logical address map

Sequence number

VersionUUID


FTL OVERVIEW: WRITE BUFFER• Open channel SSD defines minimal

write size unit, which can be multiple of block size e. g. 32K

• Write buffer collects writes before they can be submitted onto disk

BATCH 1

ENTRY 1

BATCH N

ENTRY 2 ENTRY N

ENTRY 1 ENTRY 2 ENTRY N


FTL OVERVIEW: RELOCATION MODULE• Manages band’s

defragmentation process

• Each band has its own merit based on its age, write count and validity

VALID BLOCK

INVALID BLOCK

BAND BEFORE RELOCATION BAND AFTER RELOCATION


FTL OVERVIEW: ANM HANDLING• ANM: Abstracted NAND management events

• FTL processes data relocation on certain events from SSD, like read disturb or background data refresh

• It is using Asynchronous Event Information specified in Section 5.2 of the NVMe 1.3

• Vendor Specific Notification - Get Log Page -Chunk Notification Log Entry (Log Identifier D0h)

HOST

Media Handling

READ/WRITE/ERASE Physical Page

READ/WRITE/ERASE

OPEN CHANNEL SSD


Garbage Collection

NANDDIE

NANDDIE

NANDDIE

NANDDIE

ANM


Current state• NVMe* driver with modifications

for Open Channel -spdk/include/nvme_ocssd.h

• BDEV FTL module -spdk/lib/bdev/nvme/bdev_ftl.h

• FTL library - spdk/lib/ftl

• Upstreamed and merged to SPDK* 19.01


Bdev layer

OC SSD

NVMe driver

OC SSD

FTL bdev

FTL library

Open Channel API

SPDK 18.07 SPDK 19.01

FTL bdev

FTL library


DATA ISOLATION EXAMPLE

MEDIA CONTROLLER


Bdev layer

NVMe driver Open Channel API

PU0 PU1 PU2 PU3 PU4 PU5 PU6 PU7 PU8 PU9 PU10 PU11 PU10

OC SSD



MEDIA CONTROLLER


Bdev layer



OC SSD

• construct_ftl_bdev -b ftl1 -l 0-0

FTL bdev

FTL library



MEDIA CONTROLLER


Bdev layer



OC SSD


• construct_ftl_bdev -b ftl2 -l 1-4FTL bdev

FTL library

FTL bdev

FTL library



MEDIA CONTROLLER


Bdev layer



OC SSD




FTL bdev

FTL library

FTL bdev

FTL library

FTL bdev

FTL library



MEDIA CONTROLLER


Bdev layer



OC SSD




• delete_ftl_bdev -b ftl2

FTL bdev

FTL library

FTL bdev

FTL library


NEXT STEPS: Write buffer cache for 4K PLI


Bdev layer

NVMe driver

Open Channel NVMe SSD

FTL bdev

FTL library

Open Channel API

SPDK* 18.07 SPDK 19.01

Intel® Optane SSD

Nvme Bdev

NVMe API

LVOL1 LVOL2

FUTURE

FTL bdev

FTL library




Bdev layer

NVMe driver


FTL bdev

FTL library

Open Channel API

SPDK* 18.07 SPDK 19.01

Intel® Optane SSD

Nvme Bdev

NVMe API

LVOL1 LVOL2

FUTURE

FTL bdev

FTL library

VBDEV mdcache 1

VBDEV mdcache 2




Bdev layer

NVMe driver


FTL bdev

FTL library

Open Channel API

SPDK* 18.07 SPDK 19.01

Intel® Optane SSD

Nvme Bdev

NVMe API

LVOL1 LVOL2

FUTURE

FTL bdev

FTL library

VBDEV mdcache 1

VBDEV mdcache 2

VBDEV mdcache 1

VBDEV mdcache 2


NEXT STEPS: ZONED NAMESPACE SUPPORT


Bdev/ZNS layer

NVMe driver


FTL bdev

FTL library

Open Channel API

SPDK* 18.07 SPDK 19.01 FUTURE

ZNS NVMe SSD

OCSSD/ZNS adapter

FTL bdev

FTL library

ZNS API


Summary• FTL built on top of open channel provides more control to applications

• Extra control can be used to provide:

• Better isolation

• WAF reduction

• Better QoS


Summary• FTL built on top of open channel provides more control to applications

• Extra control can be used to provide:

• Better isolation

• WAF reduction

• Better QoS

Start using FTL with SPDK today: https://spdk.io/doc/ftl.html

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Wojciech Malikowski (NVM Solutions Group) · 2019-04-29 · • SDPK FTL provides block device...

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