Hello, On Thu, 17 Aug 2017 23:56:49 +0200 Oscar Segarra wrote: > Hi David, > > Thanks a lot again for your quick answer... > > *The rules in the CRUSH map will always be followed. It is not possible > for Ceph to go against that and put data into a root that shouldn't have > it.* > --> I will work on your proposal of creating two roots in the CRUSH map... > just one question more: > --> Regarding to space consumption, with this proposal, is it possible to > know how many disk space is it free in each pool? > > *The problem with a cache tier is that Ceph is going to need to promote and > evict stuff all the time (not free). A lot of people that want to use SSD > cache tiering for RBDs end up with slower performance because of this. > Christian Balzer is the expert on Cache Tiers for RBD usage. His primary > stance is that it's most likely a bad idea, but there are definite cases > where it's perfect.* > --> Christian, is there any advice for VDI --> BASE IMAGE (raw) + 1000 > linked clones (qcow2) > Have you read: http://docs.ceph.com/docs/master/rbd/rbd-openstack/ So just from the perspective of qcow2, you seem to be doomed. Windows always appears to be very chatty when it comes to I/O and also paging/swapping seemingly w/o need, rhyme or reason. A sufficiently large cache tier should help there immensely and the base image should be in cache (RAM, pagecache on the OSD servers really) all the time anyway. Sizing this and specifying the correct type of SSDs/NVMes for the cache-tier is something that only you can answer based on existing data or sufficiently detailed and realistic tests. Christian > Thanks a lot. > > > 2017-08-17 22:42 GMT+02:00 David Turner <drakonstein@xxxxxxxxx>: > > > The rules in the CRUSH map will always be followed. It is not possible > > for Ceph to go against that and put data into a root that shouldn't have it. > > > > The problem with a cache tier is that Ceph is going to need to promote and > > evict stuff all the time (not free). A lot of people that want to use SSD > > cache tiering for RBDs end up with slower performance because of this. > > Christian Balzer is the expert on Cache Tiers for RBD usage. His primary > > stance is that it's most likely a bad idea, but there are definite cases > > where it's perfect. > > > > > > On Thu, Aug 17, 2017 at 4:20 PM Oscar Segarra <oscar.segarra@xxxxxxxxx> > > wrote: > > > >> Hi David, > >> > >> Thanks a lot for your quick answer! > >> > >> *If I'm understanding you correctly, you want to have 2 different roots > >> that pools can be made using. The first being entirely SSD storage. The > >> second being HDD Storage with an SSD cache tier on top of it. * > >> --> Yes, this is what I mean. > >> > >> https://www.sebastien-han.fr/blog/2014/08/25/ceph-mix-sata- > >> and-ssd-within-the-same-box/ > >> --> I'm not an expert in CRUSH rules... Whit this configuration, it is > >> guaranteed that objects stored in ssd pool do not "go" to the hdd disks? > >> > >> *The above guide explains how to set up the HDD root and the SSD root. > >> After that all you do is create a pool on the HDD root for RBDs, a pool on > >> the SSD root for a cache tier to use with the HDD pool, and then a a pool > >> on the SSD root for RBDs. There aren't actually a lot of use cases out > >> there where using an SSD cache tier on top of an HDD RBD pool is what you > >> really want. I would recommend testing this thoroughly and comparing your > >> performance to just a standard HDD pool for RBDs without a cache tier.* > >> --> I'm working on a VDI solution where there are BASE IMAGES (raw) and > >> qcow2 linked clones... where I expect not all VDIs to be powered on at the > >> same time and perform a configuration to avoid problems related to login > >> storm. (1000 hosts) > >> --> Do you think it is not a good idea? do you know what does usually > >> people configure for this kind of scenarios? > >> > >> Thanks a lot. > >> > >> > >> 2017-08-17 21:31 GMT+02:00 David Turner <drakonstein@xxxxxxxxx>: > >> > >>> If I'm understanding you correctly, you want to have 2 different roots > >>> that pools can be made using. The first being entirely SSD storage. The > >>> second being HDD Storage with an SSD cache tier on top of it. > >>> > >>> https://www.sebastien-han.fr/blog/2014/08/25/ceph-mix-sata- > >>> and-ssd-within-the-same-box/ > >>> > >>> The above guide explains how to set up the HDD root and the SSD root. > >>> After that all you do is create a pool on the HDD root for RBDs, a pool on > >>> the SSD root for a cache tier to use with the HDD pool, and then a a pool > >>> on the SSD root for RBDs. There aren't actually a lot of use cases out > >>> there where using an SSD cache tier on top of an HDD RBD pool is what you > >>> really want. I would recommend testing this thoroughly and comparing your > >>> performance to just a standard HDD pool for RBDs without a cache tier. > >>> > >>> On Thu, Aug 17, 2017 at 3:18 PM Oscar Segarra <oscar.segarra@xxxxxxxxx> > >>> wrote: > >>> > >>>> Hi, > >>>> > >>>> Sorry guys, during theese days I'm asking a lot about how to distribute > >>>> my data. > >>>> > >>>> I have two kinds of VM: > >>>> > >>>> 1.- Management VMs (linux) --> Full SSD dedicated disks > >>>> 2.- Windows VM --> SSD + HHD (with tiering). > >>>> > >>>> I'm working on installing two clusters on the same host but I'm > >>>> encountering lots of problems as named clusters look not be fully supported. > >>>> > >>>> In the same cluster, Is there any way to distribute my VMs as I like? > >>>> > >>>> Thanks a lot! > >>>> > >>>> Ó. > >>>> _______________________________________________ > >>>> ceph-users mailing list > >>>> ceph-users@xxxxxxxxxxxxxx > >>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > >>>> > >>> > >> -- Christian Balzer Network/Systems Engineer chibi@xxxxxxx Rakuten Communications _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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