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Editor to share with you why not all ssd are suitable for ceph journal storage, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

The company purchased some ssd to optimize the ceph cluster, and flashcache used the ssd;journal of intel 530s to make use of intel520's ssd. Today, when I read the article of sebastien, not all ssd are suitable for journal storage. This is related to the storage mechanism of journal, and journal writes are D_SYN and O_DIRECT. O_DIRECT refers to writing directly to disk without going through kernel's page cache; D_SYN means that the system ensures that each write operation is completed before it is returned. The ssd results of online test 520s and 530s are as follows:

~ # dd if=randfile.gz of=/dev/sda bs=350k count=10000 oflag=direct,dsync3584000000 bytes (3 GB 6 GB) copied, 22287 s, 161 MB/s~# dd if=randfile.gz of=/dev/sdb bs=350k count=10000 oflag=direct,dsync3584000000 bytes (3 people 6 GB) copied, 136505 s, 26jung 3 MB/s

You can also test the ssd at hand. First, turn off the write cache function of disk:

$sudo hdparm-W 0 / dev/hda 0

Then you can test your ssd with fio or dd:

$sudo fio-filename=/dev/sda-direct=1-sync=1-rw=write-bs=4k-numjobs=2-group_reporting-invalidate=0-name=journal-test$ sudo dd if=randfile of=/dev/sda bs=4k count=100000 oflag=direct,dsync

It is best to test ssd before using it in a production environment.

In addition, when using ssd, it is best to reserve some space for each ssd not to use. For example, the ssd of a 120GB can reserve 5-10GB, which can effectively increase the life of the ssd and improve some performance.

The above is all the contents of the article "Why not all ssd are suitable for ceph journal storage". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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