This would be in addition to having the journal on SSD. The journal doesn't help at all with small random reads and has a fairly limited ability to coalesce writes. In my case, the SSDs we are using for journals should have plenty of bandwidth/IOPs/space to spare, so I want to see if I can get a little more out of them. -Brendan ________________________________________ From: Noah Mehl [noahmehl@xxxxxxxxxxxxxxxxxx] Sent: Monday, March 23, 2015 1:45 PM To: Brendan Moloney Cc: ceph-users@xxxxxxxxxxxxxx Subject: Re: OSD + Flashcache + udev + Partition uuid We deployed with just putting the journal on an SSD directly, why would this not work for you? Just wondering really :) Thanks! ~Noah > On Mar 23, 2015, at 4:36 PM, Brendan Moloney <moloney@xxxxxxxx> wrote: > > I have been looking at the options for SSD caching for a bit now. Here is my take on the current options: > > 1) bcache - Seems to have lots of reliability issues mentioned on mailing list with little sign of improvement. > > 2) flashcache - Seems to be no longer (or minimally?) developed/maintained, instead folks are working on the fork enhanceio. > > 3) enhanceio - Fork of flashcache. Dropped the ability to skip caching on sequential writes, which many folks have claimed is important for Ceph OSD caching performance. (see: https://github.com/stec-inc/EnhanceIO/issues/32) > > 4) LVM cache (dm-cache) - There is now a user friendly way to use dm-cache, through LVM. Allows sequential writes to be skipped. You need a pretty recent kernel. > > I am going to be trying out LVM cache on my own cluster in the next few weeks. I will share my results here on the mailing list. If anyone else has tried it out I would love to hear about it. > > -Brendan > >> In a long term use I also had some issues with flashcache and enhanceio. I've noticed frequent slow requests. >> >> Andrei > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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