#fstrim

Enabling fstrim on various storage layers

dm-crypt

/etc/crypttab sda1_crypt         /dev/sda1          none             luks,discard

LVM

/etc/lvm/lvm.conf (...) devices {   (...)   issue_discards = 1   (...) } (...)

Filesystem

Fstrim on any filesystem can be enabled by adding discard flag to fstab. Since it will trigger defragmentation and deletion of freed blocks on every remove operation at filesystem level, it’s highly discouraged to do so. Instead one should run fstrim command periodically. Shedule should be adjusted to a particular use case. Command to check which devices support fstrim:

#lsblk -o KNAME,DISC-MAX KNAME DISC-MAX sda         2G sda1        2G sda2        2G dm-0        2G dm-1        2G

#cat /sys/block/sda/queue/discard_max_bytes 2147450880

Those with DISC-MAX of non zero value do support fstrim.

QEMU

To leverage fstrim inside domain we have to setup disk bus to utilise SCSI and SCSI controller to VirtIO SCSI:

<controller type='scsi' index='0' model='virtio-scsi'>   <alias name='scsi0'/>    <address type='pci' domain='0x0000' bus='0x02' slot='0x03' function='0x0'/> </controller> <disk type='network' device='disk'> (..)   <target dev='sda' bus='scsi'/> (...)

Then we add discard='unmap' option to disk definition:

<driver name='qemu' type='raw' cache='writeback' discard='unmap'/>

Creating LVM thin pool and thin pool volumes

At first, install thin_check tool, eg. in Ubuntu run:

apt install thin-provisioning-tools

Create optimally aligned partition for physical volume using parted:

# parted -a optimal /dev/sdb mkpart pri 0% 200G

# parted /dev/sdb align-check optimal 1 1 aligned

Create LVM physical volume and volume group:

# pvcreate /dev/sdb1  Physical volume "/dev/sdb1" successfully created.

# vgcreate vg1 /dev/sdb1  Volume group "vg1" successfully created

Create thin pool volume for thin volumes allocation:

# lvcreate --type thin-pool --extents 47635 --name  vg1-thin-pool vg1  Using default stripesize 64,00 KiB.  Thin pool volume with chunk size 128,00 KiB can address at most 31,62 TiB of data.  Logical volume "vg1-thin-pool" created.

Finally create logical volume withing previously created thin pool:

Edit /etc/default/grub and add rd.luks.options=discard at the end of the option list in GRUB_CMDLINE_LINUX_DEFAULT="..."

Edit /etc/default/grub and add :allow-discards after cryptdevice=...

If you have lvm installed edit /etc/lvm/lvm.conf and set issue_discards to 1

Run  sudo grub-mkconfig -o /boot/grub/grub.cfg

Reboot te system

Short version - Root your phone. Then use this fstrim app called LagFig. 

My Phone

My Motorola Razr Maxx has been lagging for like 5-6 months now. It seemed to start a few months after Moto updated the Razr software to Ice Cream Sandwich (4.1.2, in this case). I deleted a ton of stuff, even did a factory reset...but I could tell nothing was really solving the issue. Sometimse a simple search in Google Now would take 2-3 minutes to process. Nightmare. Before the lag set in, the phone was amazing. Every time I used it I was in awe. I get 30-ish hours of battery life and I can tether my laptop(s) off of it for hours and get Verizon 4g anywhere. That is honestly my main attraction to Moto's Maxx series of phones - the battery life. It is second to none.

And all of the other phones that have come in the past year and 1/2 are nice, but they are essentially just spec bumps. There wasn't anything I could do on them that I was missing from my Razr Maxx. But that lag set in and I've been readying myself to get a new phone...finally. Begrudgingly. 

What's Trim?

Look, I'm too lazy to copy/paste all of the technical details, but when you're using a solid state device, sometimes the controller doesn't realize that deleted blocks are available again to be written. This causes things to REALLY slow down. Trim allows those deleted blocks to be rewritten.

When I put an SSD in my Macbook Pro, I downloaded a little app called "Trim Enabler". Apple enables Trim on all of their SSD's they ship with their macs by default. When you install your own SSD, you have to use an app like that one to enable it. Pro-tip, i guess? Benchmarks showed the Samsung SSD that I had installed was writing a bit faster after.

I had noticed a lot of people were complaining about their 2012 Nexus 7 tablets lagging around the internet, and Google claimed that the new Android 4.3 fixed the lag because it used Trim. AHA! So if Trim made my SSD in my Macbook Pro faster, and Google included it in 4.3 and claimed that it fixed the Nexus 7 lag, surely there had to be a way to enable Trim on my Razr Maxx and hopefully get it running smoothly again? How to get Trim for my Razr Maxx which can't be updated to 4.3 yet? Well, I found an app. You need to be rooted but it works. It did its thing for 5 minutes, I restarted my phone, and my phone is as good as new! I just used the default settings. I think I can put off buying a new phone for a few months now until something really revolutionary hits the market.

Android 4.3 brings TRIM to Nexus devices

Android 4.3 brings TRIM to Nexus devices

Expect to spend less time maintaining your Nexus tablet or handset now that Google has enabled TRIM for most of their official hardware. Android 4.3 has now gone live, and for the most part we may not notice much of a different between the fresh and dated Jelly Beans.  For Nexus 7s and 4...