Translation(s): none

This page is about optimal set up of a SSD (Solid State Drive). This page should be kept clean enough for beginners to get the most basic idea.

Contents

  1. Basics
  2. Partitions and Alignment
  3. Mounting SSD filesystems
  4. Reduction of SSD write frequency via RAMDISK
  5. Persistent RAMDISK
  6. Low-Latency IO-Scheduler
  7. /etc/fstab example
  8. /etc/lvm/lvm.conf example
  9. Smaller system with SSD
  10. Adding vm.swappiness=0 in sysctl for the kernel
  11. SSD related bug reports

Basics

These may also help:

Partitions and Alignment

You should consider to use the Multi HDD/SSD Partition Scheme to keep variable and bulk data on the HDD(s) and establish a fallback redundancy, if the system also has a HDD available (internal or external spinning disk).

Since wheezy all tools should automatically align filesystems and partitions to the 4096 byte page size. This is one of the most important optimization aspects. Here are good links for this subject:

Mounting SSD filesystems

The performance of SSDs is also be influenced by filesystem mounting options:

Note that using discard with on-disk-cryptography (like dm-crypt) also has drawbacks with respect to security/cryptography! See crypttab(5).

dm-crypt's /etc/crypttab: 

#<target name>    <source device>            <key file>  <options>
var  UUID=01234567-89ab-cdef-0123-456789abcdef  none  luks,discard

Reduction of SSD write frequency via RAMDISK

Use of RAMDISK can stop constantly changing files from hitting on the SSD (it may hit SSD via swap). RAMDISK configuration may be performed via

Enabling RAMTMP may cause some (broken) applications to run out of temporary write disk space. Setting TMPDIR environment variable for those programs pointing to a writable disk space should fix their situation.

Please note files in /tmp are wiped out upon reboot unless /etc/default/rcS is set to something other than TMPTIME=0 (if not set, 0 is the default value).

Persistent RAMDISK

As an advanced option, you may consider to use persistent RAMDISK (dedicated read/write RAM buffer that gets synced periodically and on startup/shutdown) with anything-sync-daemon or goanysync set up:

Options to having logs copied into RAM:

If /home is not on a persistent ramdisk, use profile-sync-daemon to have the browser database and cache copied into RAM during uptime (http://ubuntuforums.org/showthread.php?t=1921800 https://github.com/graysky2/profile-sync-daemon)

Further improvement: Patch anything-sync-daemon or goanysync to use a (copy-on-write) union filesystem mount (e.g. http://aufs.sourceforge.net) to keep changes in RAM and only save to SSD on unmount/shutdown (aubrsync), instead of copying all data to RAM and having to sync it all back.

Low-Latency IO-Scheduler

The default I/O scheduler queues data to minimize seeks on HDDs, which is not necessary for SSDs. Thus, use the deadline scheduler that just ensures bulk transactions won't slow down small transactions: Install sysfsutils and

(adjust sdX to match your SSD) reboot or

In system with different drive types use can adjust settings by udev rule (put to /etc/rules.d/60-ssd-scheduler.rules): 

# set deadline scheduler for non-rotating disks
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="deadline"

The dumb "noop" scheduler may be a little faster in benchmarks that max out the throughput, but cause noticeable delays for other tasks when large file transfers are going on.

/etc/fstab example

Here is an example of /etc/fstab 

# /etc/fstab: static file system information.
#
# Use 'vol_id --uuid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
### SSD: discard,noatime
### match battery operation default for commit JOURNAL_COMMIT_TIME_AC in Add files in /etc/pm/config.d/*
/dev/mapper/goofy-root /               ext4    discard,noatime,commit=600,errors=remount-ro 0       1
# /boot was on /dev/sda1 during installation
UUID=709cbe4a-80c1-46cb-8bb1-dbce3059d1f7 /boot           ext4    discard,noatime,commit=600,defaults        0       2
### SSD: discard
/dev/mapper/goofy-swap none            swap    sw,discard              0       0
/dev/mapper/goofy-chroot /srv/chroot         btrfs    ssd,discard,noatime 0       2
/dev/scd0       /media/cdrom0   udf,iso9660 user,noauto     0       0

/etc/lvm/lvm.conf example

...
# This section allows you to configure which block devices should
# be used by the LVM system.
devices {
...
    # Issue discards to a logical volumes's underlying physical volume(s) when
    # the logical volume is no longer using the physical volumes' space (e.g.
    # lvremove, lvreduce, etc).  Discards inform the storage that a region is
    # no longer in use.  Storage that supports discards advertise the protocol
    # specific way discards should be issued by the kernel (TRIM, UNMAP, or
    # WRITE SAME with UNMAP bit set).  Not all storage will support or benefit
    # from discards but SSDs and thinly provisioned LUNs generally do.  If set
    # to 1, discards will only be issued if both the storage and kernel provide
    # support.
    # 1 enables; 0 disables.
    #issue_discards = 0
    issue_discards = 1
}
...

Smaller system with SSD

See

Adding vm.swappiness=0 in sysctl for the kernel

As per http://evolvisforge.blog.tarent.de/archives/68 which has come on p.d.o. as well as on 29/07/2013 the following needs to be added in /etc/sysctl.conf.d/ for better longevity of the disc: 

# /etc/sysctl.d/local.conf

vm.swappiness=0

}

This is a list of SSD related bug reports. It is probably better to come up with a user tag to use instead of listing them all here.