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How to set up a journal on SSD for HDD?

asked 2014-02-19 11:34:46 -0500

Bucic gravatar image

How to use " the SSD as the journal device for filesystems on spinning media"? Please provide a variant including means for reduction of excessive writes to SSD.

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answered 2014-02-20 07:39:28 -0500

Performance can be improved on journalling filesystems by moving the filesystem's journal to an external device. The low latency of solid state drives make them an ideal journalling device, offering a convenient way to improve access time and overall performance for large filesystems.

This method does not provide any means for reducing writes to the SSD. Explore other options to reduce usage of your solid state drive.

First, create the journal device. Around 100MB should be enough for even large filesystems. It can be a standard partition, LVM device, or other virtual block device, but it must be dedicated. Use whatever tools you're familiar with, ie:

parted /dev/sda mkpart

Format the partition as a journalling device:

mke2fs -O journal_dev /dev/sda6 -L home-journal

Unmount your filesystem, and configure it to use the new journal:

umount /home
tune2fs -O ^has_journal /dev/mapper/home
tune2fs -o journal_data -j -J device=LABEL=home-journal /dev/mapper/home
mount -a

These instructions cover one specific situation, an SSD with unallocated space and an LVM logical volume named /dev/mapper/home. The method can be used in a variety of other situations. man mkfs.ext4 has detailed information on ext4 options.

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Asked: 2014-02-19 11:34:46 -0500

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Last updated: Feb 20 '14