You should consider to use theMulti HDD/SSD Partition Schemeto 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:
The "discard" options with on-disk-cryptography (like dm-crypt) havedrawbacks with security/cryptography.
See crypttab(5).
Example for dm-crypt's /etc/crypttab:
# var UUID=01234567-89ab-cdef-0123-456789abcdef none luks,discard<source>
After changing filesystem options, update settings in all initramfs images:
$ sudo update-initramfs -u -k all
Alternative to setting the "discard" options is to set up an offline-trim cronjob that runstime fstrim -v (or mdtrim) on the ssd mountpoints periodically. Until software raid (md device layer) has trim support, you could use something like mdtrim (https://github.com/Cyberax/mdtrim/).
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
Set RAMTMP, RAMRUN and RAMLOCK to "yes" (in /etc/default/rcS or /etc/default/tmpfs since wheezy)
/etc/fstab: line such as "tmpfs /tmp tmpfs noatime,nosuid 0 0"
Optionally, make system only flush data to the disk every 10 minutes or more:
Kernel settings like the "dirty_buffer_ratio" etc. may only be available as non-path/mount specific global settings.
Mount option "commit=600" in /etc/fstab. See mount(8).
Or better, use pm-utils (Debian BTS #659260), tlp, or laptop-mode-tools (also optimizes read buffers) to configure the laptop-mode even under AC operation.
Attention: Increasing the flushing interval from the default 5 seconds (maybe even until proper shutdown) leaves your data much more vulnerable in case of lock-ups or power failures, and seems to be a global setting.
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:
/home (synced to work-data-fs raid only once a day?), you only risk settings the true work in /home/*/work-data is on a dedicated raid
/home/*/work-data/volatile (synced more frequently, once per hour?)
/home/*/Downloads (synced to bulk-data-fs once a day?)
/var completely if supported (syncing once a day? avoids spin-ups and allows to save /var also to SSD), at least set this up for
/var/log if supported
/var/cache/apt/archives
Configure apt to delete package files after installing, to minimize the data to sync.
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
In systems with different drive types you can adjust settings with audevrule (create /etc/udev/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"
To check if the kernel knows about SSDs try:
# for f in /sys/block/sd?/queue/rotational; do printf "$f is "; cat $f; done /sys/block/sda/queue/rotational is 1 /sys/block/sdb/queue/rotational is 1 /sys/block/sdc/queue/rotational is 0 <=== Only this is SSD!
# for f in /sys/block/sd?/queue/scheduler; do printf "$f is "; cat $f; done /sys/block/sda/queue/scheduler is noop deadline [cfq] /sys/block/sdb/queue/scheduler is noop deadline [cfq] /sys/block/sdc/queue/scheduler is noop [deadline] cfq <== That is!
The dumb "noop" scheduler may be a little faster in benchmarks that max out the throughput, but this scheduler causes noticeable delays for other tasks while large file transfers are in progress.
/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). # # ### 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 } ...
As perhttp://evolvisforge.blog.tarent.de/archives/68which 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:
Some problems might occur due to firmware bugs. Therefore, use tools likesmartctl(terminal) orGSmartControl(GUI) to check for warnings to update the firmware.Normally the manufacturer provides these proprietary firmware images packed within update tools, available as bootable CD ISO images.
In case they used FreeDOS started by syslinux, instead of booting from CD, you can extract the (floppy) image inside the ISO and create a new entry in your GRUB2 boot menu.
For the Crucial m4 firmware update, thesyslinux.cfglooks like this:
LABEL default KERNEL memdisk append initrd=boot2880.img floppy raw
Copying the filesmemdiskandboot2880.imgto the boot partition allows them to be started from GRUB2, by adding an entry in/etc/grub.d/40_custom:
# assuming an ext2 boot partition on (hd0,5) -- compare to your other GRUB2 entries menuentry "m4 firmware update" { insmod ext2 linux16 (hd0,5)/isos/m4memdisk floppy raw initrd16 (hd0,5)/isos/boot2880.img }
Afterwards runupdate-grubto apply the changes. Reboot and select the created boot entry, then follow the firmware update menu. After completion, restart the computer.
SSD related bug reports
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.
Alternative to setting the "discard" options is to set up an offline-trim cronjob that runs time fstrim -v (or mdtrim) on the ssd mountpoints periodically. Until software raid (md device layer) has trim support, you could use something like mdtrim (https://github.com/Cyberax/mdtrim/).
Attention: Increasing the flushing interval from the default 5 seconds (maybe even until proper shutdown) leaves your data much more vulnerable in case of lock-ups or power failures, and seems to be a global setting.