• Diff for "SSDOptimization"

Translation(s): none

This describe SDD optimization with system having encrypted root and swap.

An important aspect in optimizing SSD performance is the file system and partition layout. This wiki page does not yet cover these issues.

Reducing writes to solid state disks (SSDs) or laptop hard disk drives (HDDs)

• Disable or reduce disk writes during disk read access.
  • Set "noatime" or "relatime" mount option in /etc/fstab.
• set RAMTMP, RAMRUN and RAMLOCK to "yes" in /etc/default/tmpfs (since wheezy)

  • RAMTMP will keep /tmp in RAM only, causing its content to be discarded on shutdown! Using increasing the commit interval or using sync scripts (see below) shall reduce disk writes significantly without regularly discarding data.

• Make system flush data to the disk every 10 minutes for laptop PCs.

  Attention: Changing the flushing interval from default 5 seconds to 10 minutes (or until proper shutdown) makes your data more vulnerable in case of lock-ups or power failures.

  • Manually set "commit=600" mount option in /etc/fstab. See mount(8).

  • Or better, set up pm-utils (Debian BTS #659260) or laptop-mode-tools to enable laptop-mode even under AC operation.

  • Alternatively, and more selective than changing the global commit interval:

    • 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)

    • consider having logs copied into RAM with http://www.debian-administration.org/articles/661, http://www.tremende.com/ramlog or https://github.com/graysky2/anything-sync-daemon

Optimizations for solid state disks (SSDs)

Performance and disk wear of the solid state drive (SSD) can be optimized as follows.

• Use the latest Linux kernel. (>3.2)

• Enable the TRIM command.
  • Set "discard" mount option in /etc/fstab for the ext4 filesystem, swap partition, Btrfs, etc. See mount(8).

    • Alternativly, set up an offline-trim cronjob that runs time fstrim -v  on the ssd mountpoints periodically (enabling online-trim in fstab may slow down some SSDs).

  • Set "discard" option in /etc/lvm/lvm.conf for LVM. See lvm.conf(5).
  • Set "discard" option in /etc/crypttab for dm-crypt.

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

dm-crypt: /etc/crypttab

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

• You'll also need to update your initramfs: update-initramfs -u -k all

• With btrfs, enable the SSD optimized disk space allocation scheme.
  • Set "ssd" mount option in /etc/fstab.

More: http://siduction.org/index.php?module=news&func=display&sid=78 http://forums.debian.net/viewtopic.php?f=16&t=76921 https://wiki.archlinux.org/index.php/SSD

/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

...
# 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

• http://wiki.debian.org/DebianAcerOne?highlight=%28SSD%29#Reducing_Disk_Access_for_laptops_with_SSDs