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| Solid-state disks have low-level block fragmentation problems (see Anandtech article), and these problems will persist even after formatting. Most disk's block mapping table can be reset by [[http://ata.wiki.kernel.org/index.php/ATA_Secure_Erase|issuing an ATA secure erase command]]. | <<TableOfContents>> Solid-state disks have low-level block fragmentation problems (see Anandtech article), and these problems will persist even after formatting. Most disk's block mapping table can be reset by [[https://ata.wiki.kernel.org/articles/a/t/a/ATA_Secure_Erase_936d.html|issuing an ATA secure erase command]]. == Disable entropy collection from disk I/O == With rotating disks, the amount of time to write a block is used as source of entropy. With SSDs, the time is so fast that it no longer is a good entropy source. The code path to verify randomness and add this data to the entropy pool just serves as a slowdown, but it can be disabled with: {{{ echo 0 > /sys/block/sda/queue/add_random }}} This will work with Linux 2.6.36 and above. |
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| * [[http://lifehacker.com/5342636/how-to-fix-annoying-youtube-jumpiness-in-firefox|Reduce Firefox's Session Saving frequency]] | === Reduce Firefox's Session Saving frequency === [[http://lifehacker.com/5342636/how-to-fix-annoying-youtube-jumpiness-in-firefox|Reduce Firefox's Session Saving frequency]] mentions to alter the default of 15s to 60s, or perhaps 300s (5 minutes). In about:config, set browser.sessionstore.interval to 60000. |
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== /var/lock and /var/run on a RAM disk == Ubuntu puts /var/lock and /var/run into a RAM disk; you can do the same with Debian by configuring the appropriate settings in /etc/default/rcS: {{{#!highlight sh cat << EOF >> /etc/default/rcS RAMRUN=yes RAMLOCK=yes EOF }}} This may break some buggy packages. == Creating aligned filesystems == This assume that the underlying partitions (including layers, such as LVM) have been created on properly-aligned sector boundaries. These assume a 128 KiB erase block size. More information: * [[http://thunk.org/tytso/blog/2009/02/20/aligning-filesystems-to-an-ssds-erase-block-size/| Aligning filesystems to an SSD's erase block size]] (Theodore Ts'o) === ext4 === {{{ mkfs -t ext4 -E stripe-width=32,resize=$(FILESYSTEM_SIZE)*10G /dev/sda1 }}} Set the resize parameter to 10 times the filesystem's size, assuming that in the future you might grow the filesystem that large. The default multiplier is 1000, which is definitely unreasonable. Remember to append 'G' for gigabytes. Source: [[http://thunk.org/tytso/blog/2009/02/20/aligning-filesystems-to-an-ssds-erase-block-size/|Aligning filesystems to an SSD's erase block size]] This can also be down at mount time: {{{ mount -t ext4 -o stripe=32 /dev/sda1 }}} The stripe parameter multiplied by kernel's page size (4 KiB) will be the erase block size. I.e. 32 * 4 KiB = 128 KiB. === XFS === {{{ mkfs -t xfs -d su=128k -d sw=1 /dev/sda1 }}} This can also be done at mount time, though the options/units are different: {{{ mount -t xfs -o sunit=256,swidth=256 /dev/sda1 }}} === NILFS2 === I believe this log-structured filesystem, by default, will already by aligned… For creation: {{{ sudo mkfs -t nilfs2 -L 'Round OCZ Rally' /dev/sdi1 }}} === UDF === Not really block-aligned, but: {{{ dd if=/dev/zero of=/dev/sdc bs=1M count=1 mkudffs -b 512 --media-type=hd /dev/sdc }}} |
Contents
Solid-state disks have low-level block fragmentation problems (see Anandtech article), and these problems will persist even after formatting. Most disk's block mapping table can be reset by issuing an ATA secure erase command.
Disable entropy collection from disk I/O
With rotating disks, the amount of time to write a block is used as source of entropy. With SSDs, the time is so fast that it no longer is a good entropy source. The code path to verify randomness and add this data to the entropy pool just serves as a slowdown, but it can be disabled with:
echo 0 > /sys/block/sda/queue/add_random
This will work with Linux 2.6.36 and above.
Reducing writes
Reduce Firefox's Session Saving frequency
Reduce Firefox's Session Saving frequency mentions to alter the default of 15s to 60s, or perhaps 300s (5 minutes). In about:config, set browser.sessionstore.interval to 60000.
Remounting temporary files as tmpfs
To /etc/fstab:
none /tmp tmpfs defaults,noatime,mode=1777,size=1024M 0 0 none /var/tmp tmpfs defaults,noatime,mode=1777,size=512M 0 0
/var/lock and /var/run on a RAM disk
Ubuntu puts /var/lock and /var/run into a RAM disk; you can do the same with Debian by configuring the appropriate settings in /etc/default/rcS:
This may break some buggy packages.
Creating aligned filesystems
This assume that the underlying partitions (including layers, such as LVM) have been created on properly-aligned sector boundaries.
These assume a 128 KiB erase block size.
More information:
Aligning filesystems to an SSD's erase block size (Theodore Ts'o)
ext4
mkfs -t ext4 -E stripe-width=32,resize=$(FILESYSTEM_SIZE)*10G /dev/sda1
Set the resize parameter to 10 times the filesystem's size, assuming that in the future you might grow the filesystem that large. The default multiplier is 1000, which is definitely unreasonable. Remember to append 'G' for gigabytes.
Source: Aligning filesystems to an SSD's erase block size
This can also be down at mount time:
mount -t ext4 -o stripe=32 /dev/sda1
The stripe parameter multiplied by kernel's page size (4 KiB) will be the erase block size. I.e. 32 * 4 KiB = 128 KiB.
XFS
mkfs -t xfs -d su=128k -d sw=1 /dev/sda1
This can also be done at mount time, though the options/units are different:
mount -t xfs -o sunit=256,swidth=256 /dev/sda1
NILFS2
I believe this log-structured filesystem, by default, will already by aligned… For creation:
sudo mkfs -t nilfs2 -L 'Round OCZ Rally' /dev/sdi1
UDF
Not really block-aligned, but:
dd if=/dev/zero of=/dev/sdc bs=1M count=1 mkudffs -b 512 --media-type=hd /dev/sdc
