SSD/NVMe Tweaks (TRIM/Discard)

Lin­ux Desk­top

Lin­ux Serv­er

Note, with­in the ex­am­ples in the fol­low­ing sec­tions, /​​​dev/​​​sda refers to a SSD de­vice while /​​​dev/​​​nvme0n1 refers to a NVMe de­vice.

Dis­card­ing Un­used Blocks

You can per­form or sched­ule dis­card op­er­a­tions on block de­vices that sup­port them. Block dis­card op­er­a­tions dis­card blocks that are no longer in use by a mount­ed file sys­tem. They are use­ful on:

• Sol­id-state dri­ves (SS­Ds)
• Thin­ly-pro­vi­sioned stor­age

You can run dis­card op­er­a­tions us­ing dif­fer­ent meth­ods:

Batch dis­card

Are run ex­plic­it­ly by the user. They dis­card all un­used blocks in the se­lect­ed file sys­tems.

On­line dis­card

Are spec­i­fied at mount time. They run in re­al time with­out user in­ter­ven­tion. On­line dis­card op­er­a­tions dis­card on­ly the blocks that are tran­si­tion­ing from used to free.

Pe­ri­od­ic dis­card

Are batch op­er­a­tions that are run reg­u­lar­ly by a sys­temd ser­vice.

All types are sup­port­ed by the XFS and ext4 file sys­tems and by VDO.

Rec­om­men­da­tions

Red Hat rec­om­mends that you use batch or pe­ri­od­ic dis­card.

Use on­line dis­card on­ly if:

• the system’s work­load is such that batch dis­card is not fea­si­ble, or
• on­line dis­card op­er­a­tions are nec­es­sary to main­tain per­for­mance.

Ref­er­ences

• Red Hat Docs: Red Hat > [8] > Man­ag­ing stor­age de­vices > Chap­ter 8. Dis­card­ing un­used blocks
• Red Hat Docs: Red Hat > [9] > Man­ag­ing stor­age de­vices > Chap­ter 10. En­abling mul­ti­pathing on NVMe de­vices
• Red Hat Docs: Red Hat > [9] > Man­ag­ing stor­age de­vices > Chap­ter 37. Dis­card­ing un­used blocks

Get Full SSD/​​​NVMe/​​​HDD De­vice In­fo

For SSD/HDD de­vices use:

smartctl -x /dev/sda            # -x, --xall; -a, --all

hdparm -I /dev/sda              # doesn't support NVMe

For NVMe de­vices use:

smartctl -x /dev/nvme0n1        # -x, --xall; -a, --all

nvme smart-log -H /dev/nvme0n1  # apt install nvme-cli

Ref­er­ences

• Smart­Mon­Tools: NVMe sup­port
• Per­cona: Us­ing NVMe Com­mand Line Tools to Check NVMe Flash Health
• Unix and Lin­ux: How to eval­u­ate the wear lev­el of a NVMe SSD?
• NVMexpress​.org: NVMe Cur­rent Spec­i­fi­ca­tions
• Lin­ux NVMe at GitHub: nvme-cli

[Batch dis­card] TRIM from CLI

fstrim com­mand

sudo fstrim -av             # trim/discardd all mounted devices, verbose output
sudo fstrim -v /            # trim/discardd the root fs, verbose output
sudo fstrim /mount-point    # trim/discardd a device mounted at specific mount point

Prox­moxVE Node

For unpriv­i­leged Lin­ux con­tain­ers use the fol­low­ing com­mand at the Prox­moxVE host side .

pct fstrim 151              # Where 151 is the Id of the container

For priv­i­leged con­tain­ers fstrim could be ex­e­cut­ed al­so from the guest's side. For the vir­tu­al ma­chines – en­able the dis­card and SSD em­u­la­tion op­tions in the stor­age de­vice con­fig­u­ra­tion, use Vir­tIo SC­SI as con­troller and trim at the guest side. Al­so we can use one of the fol­low­ing com­mands at he Prox­moxVE host side.

qm guest cmd 251 fstrim     # Where 251 is the Id of the container

qm agent 251 fstrim         # Where 251 is the Id of the container

[Pe­ri­od­ic Dis­card] Set the TRIM Job to Dai­ly

sudo systemctl enable fstrim.timer

sudo mkdir /etc/systemd/system/fstrim.timer.d
sudo nano /etc/systemd/system/fstrim.timer.d/override.conf

[Timer]
OnCalendar=
OnCalendar=daily

Re­boot the sys­tem or do dae­mon-re­load and check the up­dat­ed val­ue.

sudo systemctl daemon-reload

systemctl cat fstrim.timer

# /lib/systemd/system/fstrim.timer
[Unit]
Description=Discard unused blocks once a week
Documentation=man:fstrim
ConditionVirtualization=!container

[Timer]
OnCalendar=weekly
AccuracySec=1h
Persistent=true

[Install]
WantedBy=timers.target

# /etc/systemd/system/fstrim.timer.d/override.conf
[Timer]
OnCalendar=
OnCalendar=daily

sudo systemctl status fstrim.service
sudo systemctl status fstrim.timer

Un­do the change if you need.

sudo rm -v /etc/systemd/system/fstrim.timer.d/override.conf

Ref­er­ences

• Easy Lin­ux Tips Project: SSD – How to op­ti­mize your Sol­id State Dri­ve for Lin­ux Mint and Ubun­tu

[On­line Dis­card] En­able TRIM in /​​​etc/​​​fstab

This ap­proach is not rec­om­mend­ed by the most man­u­als.

sudo nano /etc/fstab

#/dev/disk/by-uuid/09e7c8ed-fb55-4a44-8be4-18b1696fc714 / ext4 defaults 0 0
/dev/disk/by-uuid/09e7c8ed-fb55-4a44-8be4-18b1696fc714 / ext4 discard,async,noatime,nodiratime,errors=remount-ro 0 1

Warn­ing: Users need to be cer­tain that their SSD sup­ports TRIM be­fore at­tempt­ing to use it. Da­ta loss can oc­cur oth­er­wise! To test whether the SSD de­vice sup­ports TRIM/​​​Discard op­tion you can use ei­ther of the fol­low­ing com­mands.

sudo hdparm -I /dev/sda | grep TRIM

* Data Set Management TRIM supported (limit 8 blocks)

sudo smartctl --all /dev/sda | grep TRIM

TRIM Command:     Available

To test does an NVMe sup­ports TRIM (phys­i­cal dis­card op­tion) the out­put of the fol­low­ing com­mand must be greater than 0. This ap­proach is ap­plic­a­ble al­so for SSD de­vices.

cat /sys/block/nvme0n1/queue/discard_max_bytes

cat /sys/block/sda/queue/discard_max_bytes

Ref­er­ences

• Arch Lin­ux Wi­ki: Sol­id state dri­ve
• Red Hat Doc­u­men­ta­tion: Red Hat En­ter­prise Lin­ux > 8 > Man­ag­ing stor­age de­vices > Chap­ter 8. Dis­card­ing un­used blocks

• How-To Geek: How to Tweak Your SSD in Ubun­tu for Bet­ter Per­for­mance
• How-To Geek: What Is the Lin­ux fstab File, and How Does It Work?
• itBeginner​.net: How to tweak and op­ti­mize SSD for Ubun­tu, Lin­ux Mint
• Ask Ubun­tu: How do I op­ti­mize the OS for SS­Ds?

Tweak the AMP val­ue of SSD

Most Lin­ux dis­tri­b­u­tions use Lin­ux Kernel’s “Ad­vanced Pow­er Man­age­ment (APM)” API to han­dle con­fig­u­ra­tion, op­ti­mize per­for­mance, and en­sure sta­bil­i­ty of stor­age de­vices. These de­vices are as­signed an APM val­ue be­tween 1 and 255 to con­trol their pow­er man­age­ment thresh­olds. A val­ue of 254 in­di­cates best per­for­mance, while a val­ue of 1 in­di­cates bet­ter pow­er man­age­ment. As­sign­ing a val­ue of 255 will dis­able APM al­to­geth­er. By de­fault, SS­Ds are as­signed an APM of 254 when the sys­tem is run­ning on ex­ter­nal pow­er. In bat­tery mode, the APM lev­el is set to 128, re­duc­ing the read and write speeds of SS­Ds. This ar­ti­cle ex­plains how to in­crease SSD APM lev­els to 254 when your Lin­ux lap­top is run­ning on bat­tery mode.

sudo hdparm -B254 /dev/sda

Get the cur­rent AMP val­ue.

sudo hdparm -B /dev/sda

Test the per­for­mance.

sudo hdparm -tT /dev/sda

Ref­er­ences

• AskUbun­tu: Ubun­tu SSD – Was fast, is now ex­treme­ly slow
• LinuxHint​.com: How to Im­prove SSD Per­for­mance in Lin­ux Lap­tops

See al­so

• Lin­ux Swap and Swap­file
• Pre­load Tool for Bet­ter Sys­tem Per­for­mance
• Arch Lin­ux Wi­ki: Im­prov­ing per­for­mance (Need to read care­ful­ly!)
• Arch Lin­ux Wi­ki: Ext4 (Need to read care­ful­ly!)
• Web­site for Stu­dents: Im­prove Ng­inx Cache Per­for­mance with tmpfs on Ubun­tu

Reg­is­ter: Lin­ux Desk­top

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