Hello, i was wondering about ceph block.db to be nearly empty and I started to investigate. The recommendations from ceph are that block.db should be at least 4% the size of block. So my OSD configuration looks like this: wal.db - not explicit specified block.db - 250GB of SSD storage block - 6TB Since wal is written to block.db if not available i didn't configured wal. With the size of 250GB we are slightly above 4%. So everything should be "fine". But the block.db only contains about 10GB of data. If figured out that an object in block.db gets "amplified" so the space consumption is much higher than the object itself would need. I'm using ceph as storage backend for openstack and raw images with a size of 10GB and more are common. So if i understand this correct i have to consider that a 10GB images may consume 100GB of block.db. Beside the facts that the image may have a size of 100G and they are only used for initial reads unitl all changed blocks gets written to a SSD-only pool i was question me if i need a block.db and if it would be better to save the amount of SSD space used for block.db and just create a 10GB wal.db? Has anyone done this before? Anyone who had sufficient SSD space but stick with wal.db to save SSD space? If i'm correct the block.db will never be used for huge images. And even though it may be used for one or two images does this make sense? The images are used initially to read all unchanged blocks from it. After a while each VM should access the images pool less and less due to the changes made in the VM. Any thoughts about this? Best regards -- Benjamin Zapiec <benjamin.zapiec@xxxxxxxxxx> (System Engineer) * GONICUS GmbH * Moehnestrasse 55 (Kaiserhaus) * D-59755 Arnsberg * Tel.: +49 2932 916-0 * Fax: +49 2932 916-245 * http://www.GONICUS.de * Sitz der Gesellschaft: Moehnestrasse 55 * D-59755 Arnsberg * Geschaeftsfuehrer: Rainer Luelsdorf, Alfred Schroeder * Vorsitzender des Beirats: Juergen Michels * Amtsgericht Arnsberg * HRB 1968 Wir erfüllen unsere Informationspflichten zum Datenschutz gem. der Artikel 13 und 14 DS-GVO durch Veröffentlichung auf unserer Internetseite unter: https://www.gonicus.de/datenschutz oder durch Zusendung auf Ihre formlose Anfrage.
Attachment:
signature.asc
Description: OpenPGP digital signature
_______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
