5 crucial optimizations for SSD usage in Ubuntu Linux

I bought my first SSD more than 5 years ago (late 2007), for my white MacBook Core2Duo 2.0 Ghz. It may be needless to say that my MacBook ran faster than many MacBook Pro’s at that time. The look on peoples faces when they saw my MacBook boot faster than their MacBook Pro was unforgettable.

By that time I was also experimenting with running 2 x 8GB CompactFlash with SATA converters in RAID-0 mode in my completely silent (but old and under-clocked) Pentium 3 Linux desktop. When people would visit my home they couldn’t believe my PC was actually turned on: it was dead silent.

Even today I still enjoy building low-power, silent and ultra-fast (Linux) computers with an SSD as the primary drive. Nowadays the new mSATA standard (see picture) is being used. During the past years I learned a thing or two about configuring Linux on a SSD drive. Today I will share those things with you:

1) Buy more than enough RAM

Yep, you should have at least 16GB of RAM. I know you’ll say that you don’t use that, but that is exactly the point. If you would be using it, it would not be enough. And why not? RAM is relatively cheap these days and you don’t want your system to start swapping, since this will wear out your expensive SSD.

2) Use the default partition layout

Contrary to popular belief, the default (guided) partitioning will do. If you partition manually, keep in mind that you do need a swap partition that is bigger than your RAM size.

3) Avoid using swap

You have plenty of RAM, so you could turn off swap or even create a system without swap. I have been running without swap for a year or so and never experienced significant problems (other people say the same). The most annoying side-effect is that the hibernate function is not available, since it uses the swap partition. This is why I recommend to not completely disable swap, but to reduce the swappiness of Linux. This way Linux will use all available RAM before starting to write to your precious SSD, while still allowing you to hibernate. Still, be aware when it comes to using hibernate, because it uses a lot of writes. Run this one-liner to add a permanent swappiness setting:

1	`echo -e "vm.swappiness=0" \| sudo tee -a /etc/sysctl.conf`

This will only be effective after reboot.

4) Disable access time logging

Remove the access time logging on the file system. Without the “noatime” flag on your file system every read will cause a write, because the file system will update the access time. This is bad for the life-time of your SSD, since it supports a limited number of writes and this is causing significantly more writes. Edit the “fstab” to add the “noatime” flag:

1	`sudo nano /etc/fstab`

Now change “errors=remount-ro” to “noatime,errors=remount-ro”. Save the file and reboot.

5) Enable TRIM

TRIM will stop your SSD from slowing down after using it for a while. If you do not enable TRIM the writes may become slower due to the erasing of the deleted blocks. By running this one-liner you can add TRIM as a daily cron job:

1	`echo -e "#\x21/bin/sh\\nfstrim -v /" \| sudo tee /etc/cron.daily/trim`

You have to make the cron job executable using:

1	`sudo chmod +x /etc/cron.daily/trim`

It will be run every day to avoid slowing down your writes and you will hardly notice it.

More advice: monitor the expected life-time

Your disk will not run forever. It has an expected life-time and you should probably monitor it using:

1	`sudo smartctl -data -A /dev/sda`

This will output something like this:

maurits@nuc:~$ sudo smartctl -data -A /dev/sda

smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.8.0-26-generic] (local build)

=== START OF READ SMART DATA SECTION ===

SMART Attributes Data Structure revision number: 18

Vendor Specific SMART Attributes with Thresholds:

ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE

1 Raw_Read_Error_Rate 0x0000 006 000 000 Old_age Offline - 6

3   Spin_Up_Time            0x0000   100   100   000    Old_age   Offline      -       0

4 Start_Stop_Count 0x0000 100 100 000 Old_age Offline - 0

5 Reallocated_Sector_Ct 0x0000 100 100 000 Old_age Offline - 0

9   Power_On_Hours          0x0000   100   100   000    Old_age   Offline      -       2592

12 Power_Cycle_Count 0x0000 100 100 000 Old_age Offline - 258

232 Available_Reservd_Space 0x0000 100 100 000 Old_age Offline - 4914564640

233 Media_Wearout_Indicator 0x0000 100 000 000 Old_age Offline - 100

maurits@nuc:~$

At ID# 233 you see the MWI. This is a value starting at 100 and when it reaches values below 10 you should start to worry. Note that different manufacturers may have different names and numbers for this indicator.

Final advice: avoid buying TLC drives

Triple Level Cell (TLC) drives are making their entry in the market. These drives have a dramatically lower expected life-time. The life-time of a drive is measured in Program/Erase (PE) cycles or in Peta Bytes Written (PBW). Check the specs carefully to avoid buying a cheap drive, thinking you made a good deal, while actually buying a model with a lower expected life-time.

A swap partition on your SSD will let you wake up faster from hibernation (aka "suspend to disk") as compared to swap on a hard drive. But given the incredibly fast boot time of Ubuntu when booting from SSD a wake up from hibernation may be slower than a reboot.

If you do not hibernate you may never need to swap at all.

Only in case you often have very many RAM intensive applications running in parallel, your system may eventually use swap. Then a swap on SSD will be somewhat faster than a swap on a hard drive. Still there is no need to worry about wearing of your SSD from extensive swapping.

If not used for hibernation you can alway add a swap partition or swap on file later: