\nAt the same time I read about Fedora 20 and found some pretty io mechanism called bcache.
\nIt works in a similar way to FastCache in EMC (https:\/\/www.emc.com<\/a>)<\/p>\n
However, my node was using CentOS w\/ kernel 2.6.x. Below, I present my steps to install and configure bcache.<\/p>\n
This is http:\/\/xmodulo.com<\/a> where you will find how to upgrade kernel (you must remember that you need at least 3.10, and that 3.2 < 3.10 :)). You have to mark the adequate module:\n check writeback (what happened after it is turned off)<\/p>\n Important notes:<\/p>\n – Bad write performance<\/p>\n If write performance is not what you expected, you probably wanted to be # echo 4M > \/sys\/block\/bcache0\/bcache\/sequential_cutoff<\/p>\n simple device information:<\/p>\n How to turn off bcache? # revert the device # you will obtain the cest-uuid with (condition that \/dev\/xvdg was registered as cache device) You’ll see in dmesg:<\/p>\n Or you can disable caching with the following command:<\/p>\n Very nice command! I have used bcache for last 2 months in production environment and it works fine.<\/p>\n sources: Necessity_is_the_mother_of_invention I needed some cheap solution for my slow HDDs in one of MySQL node. The box was limited to 4 HDD slots and the actual configuration w\/o RAID 1 stopped working \ud83d\ude42 At the same time I read about Fedora 20 and found some pretty io mechanism called bcache. It works in a similar […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=\/wp\/v2\/posts\/819"}],"collection":[{"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=819"}],"version-history":[{"count":20,"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=\/wp\/v2\/posts\/819\/revisions"}],"predecessor-version":[{"id":1176,"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=\/wp\/v2\/posts\/819\/revisions\/1176"}],"wp:attachment":[{"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=819"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=819"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/10sa.com\/sql_stories\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=819"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"bcache-kernel\"](\"http:\/\/10sa.com\/sql_stories\/wp-content\/uploads\/2014\/08\/bcache-kernel-300x127.png\")
<\/a><\/p>\n\r\ngit clone http:\/\/evilpiepirate.org\/git\/bcache-tools.git\r\nyum install libblkid-devel -y\r\nyum install libuuid-devel -y\r\nmake install \r\n\r\nmake-bcache --cache \/dev\/mapper\/vg_system-database\r\nmake-bcache --bdev \/dev\/mapper\/hot-mysql \r\n\r\n\r\n# Register our backing device with the new cache set:\r\necho CSET-UUID of cache device >\/sys\/block\/bcache0\/bcache\/attach\r\n<\/pre>\n
\n running in writeback mode, which isn’t the default (not due to a lack of
\n maturity, but simply because in writeback mode you’ll lose data if something
\n happens to your SSD)
\n(source: documantion)
\n To set it back to the default (4 mb), do<\/p>\n\r\nbcache-super-show \/dev\/mapper\/vg_system-database\r\n<\/pre>\n
\r\n# Backand device stats:\r\ntail -f \/sys\/block\/bcache0\/bcache\/stats_total\/*\r\n# Concrete cache device stats:\r\ntail -f \/sys\/fs\/bcache\/d09433aa-e685-4dd4-968e-dae77bb2de18\/stats_total\/*\r\n<\/pre>\n
\nunregister
\n Detaches all backing devices and closes the cache devices; if dirty data is
\n present it will disable writeback caching and wait for it to be flushed.<\/p>\n\r\necho 1 > \/sys\/fs\/bcache\/d09433aa-e685-4dd4-968e-dae77bb2de18\/unregister\r\n# now \r\nbcache-super-show \/dev\/mapper\/hot-mysql \r\ndev.data.cache_state\t0 [detached]\r\ncat \/sys\/block\/bcache0\/bcache\/dirty_data \r\n<\/pre>\n
\necho \/dev\/mapper\/vg_system-database > \/sys\/fs\/bcache\/register
\n# attach the cache (cest-uuid)
\necho d09433aa-e685-4dd4-968e-dae77bb2de18 > \/sys\/block\/bcache0\/bcache\/attach <\/p>\n
\nbcache-super-show \/dev\/xvdg | grep “cset.uuid”<\/p>\n\r\nroot>dmesg\r\nXFS (bcache0): Mounting Filesystem\r\nXFS (bcache0): Ending clean mount\r\nbcache: bch_journal_replay() journal replay done, 3 keys in 3 entries, seq 333449\r\nbcache: register_cache() registered cache device dm-4\r\nbcache: bch_cached_dev_attach() Caching dm-2 as bcache0 on set d09433aa-e685-4dd4-968e-dae77bb2de18\r\n<\/pre>\n
\r\nroot> bcache-super-show \/dev\/mapper\/hot-mysql | grep cache_state\r\ndev.data.cache_state\t1 [clean]\r\n<\/pre>\n
\r\necho none > \/sys\/block\/bcache0\/bcache\/cache_mode\r\n<\/pre>\n
\nlsblk -o NAME,MAJ:MIN,RM,SIZE,TYPE,FSTYPE,MOUNTPOINT,UUID<\/p>\n
\nhttp:\/\/www.linux.com\/learn\/tutorials\/754674-using-bcache-to-soup-up-your-sata-drive\t \thttp:\/\/forums.gentoo.org\/viewtopic-t-959542.html<\/p>\n","protected":false},"excerpt":{"rendered":"