Here it is: https://github.com/apache/cloudstack-docs-admin/pull/47
Added KVM online storage migration (atm only CEPH/NFS to SolidFire, new in 4.11 release) Added KVM cache mode setup and limitations. Cheers On 20 February 2018 at 16:49, Rafael Weingärtner < rafaelweingart...@gmail.com> wrote: > If you are willing to write it down, please do so, and open a PR. We will > review and merged it afterwards. > > On Tue, Feb 20, 2018 at 12:41 PM, Andrija Panic <andrija.pa...@gmail.com> > wrote: > > > I advise (or not...depends on point of view) to stay that way - because > > when you activate write-back cache - live migrations will stop, and this > > makes *Enable maintenance mode (put host into maintenance)* impossible. > > > > I would perhaps suggest that there is documentation for "advanced users" > or > > similar, that will say "it's possible to enable this and this way via DB > > hack, but be warned on live migration consequences etc..." since this > will > > render more problems if people start using it. > > > > If you choose to do, let me know, I can write that (documentation) > briefly. > > > > Not to mention it can be unsafe (power failure - less possible I guess, > but > > rare kernel panic etc might have it's consequences I assume) > > > > It does indeed increase performance on NFS much, but not necessarily on > > CEPH (if you are using lirbd cache on client side as explained above) > > > > On 20 February 2018 at 15:48, Rafael Weingärtner < > > rafaelweingart...@gmail.com> wrote: > > > > > Yes. Weird enough, the code is using the value in the database if it is > > > provided there, but there is no easy way for users to change that > > > configuration in the database. ¯\_(ツ)_/¯ > > > > > > On Tue, Feb 20, 2018 at 11:45 AM, Andrija Panic < > andrija.pa...@gmail.com > > > > > > wrote: > > > > > > > So it seems that just passing the cachemode value to API is not > there, > > or > > > > somehow messedup, but deployVM process does read DB values from > > > > disk_offering table for sure, and applies it to XML file for KVM. > > > > This is above ACS 4.8.x. > > > > > > > > > > > > On 20 February 2018 at 15:44, Andrija Panic <andrija.pa...@gmail.com > > > > > > wrote: > > > > > > > > > I have edited the disk_offering table, in the cache_mode just enter > > > > > "writeback". Stop and start VM, and it will pickup/inherit the > > > cache_mode > > > > > from it's parrent offering > > > > > This also applies to Compute/Service offering, again inside > > > disk_offering > > > > > table - just tested both > > > > > > > > > > i.e. > > > > > > > > > > UPDATE `cloud`.`disk_offering` SET `cache_mode`='writeback' WHERE > > > > > `id`=102; # Compute Offering (Service offering) > > > > > UPDATE `cloud`.`disk_offering` SET `cache_mode`='writeback' WHERE > > > > > `id`=114; #data disk offering > > > > > > > > > > Before SQL: > > > > > > > > > > root@ix1-c7-4:~# virsh dumpxml i-2-10-VM | grep cache -A2 > > > > > <driver name='qemu' type='qcow2' cache='none'/> > > > > > <source file='/mnt/63a3ae7b-9ea9-3884- > > > a772-1ea939ef6ec3/1b655159- > > > > > ae10-41cf-8987-f1cfb47fe453'/> > > > > > <target dev='vda' bus='virtio'/> > > > > > -- > > > > > <driver name='qemu' type='qcow2' cache='none'/> > > > > > <source file='/mnt/63a3ae7b-9ea9-3884- > > > a772-1ea939ef6ec3/09bdadcb- > > > > > ec6e-4dda-b37b-17b1a749257f'/> > > > > > <target dev='vdb' bus='virtio'/> > > > > > -- > > > > > > > > > > STOP and START VM = after SQL > > > > > > > > > > root@ix1-c7-4:~# virsh dumpxml i-2-10-VM | grep cache -A2 > > > > > <driver name='qemu' type='qcow2' cache='writeback'/> > > > > > <source file='/mnt/63a3ae7b-9ea9-3884- > > > a772-1ea939ef6ec3/1b655159- > > > > > ae10-41cf-8987-f1cfb47fe453'/> > > > > > <target dev='vda' bus='virtio'/> > > > > > -- > > > > > <driver name='qemu' type='qcow2' cache='writeback'/> > > > > > <source file='/mnt/63a3ae7b-9ea9-3884- > > > a772-1ea939ef6ec3/09bdadcb- > > > > > ec6e-4dda-b37b-17b1a749257f'/> > > > > > <target dev='vdb' bus='virtio'/> > > > > > -- > > > > > > > > > > > > > > > > > > > > On 20 February 2018 at 14:03, Rafael Weingärtner < > > > > > rafaelweingart...@gmail.com> wrote: > > > > > > > > > >> I have no idea how it can change the performance. If you look at > the > > > > >> content of the commit you provided, it is only the commit that > > enabled > > > > the > > > > >> use of getCacheMode from disk offerings. However, it is not > exposing > > > any > > > > >> way to users to change that value/configuration in the database. I > > > might > > > > >> have missed it; do you see any API methods that receive the > > parameter > > > > >> "cacheMode" and then pass this parameter to a "diskOffering" > object, > > > and > > > > >> then persist/update this object in the database? > > > > >> > > > > >> May I ask how are you guys changing the cacheMode configuration? > > > > >> > > > > >> On Tue, Feb 20, 2018 at 9:56 AM, Paul Angus < > > paul.an...@shapeblue.com > > > > > > > > >> wrote: > > > > >> > > > > >> > I'm working with some guys who are experimenting with the > setting > > as > > > > if > > > > >> > definitely seems to change the performance of data disks. It > also > > > > >> changes > > > > >> > the XML of the VM which is created. > > > > >> > > > > > >> > p.s. > > > > >> > I've found this commit; > > > > >> > > > > > >> > https://github.com/apache/cloudstack/commit/1edaa36cc68e845a > > > > >> 42339d5f267d49 > > > > >> > c82343aefb > > > > >> > > > > > >> > so I've got something to investigate now, but API documentation > > must > > > > >> > definitely be askew. > > > > >> > > > > > >> > > > > > >> > > > > > >> > paul.an...@shapeblue.com > > > > >> > www.shapeblue.com > > > > >> > 53 Chandos Place, Covent Garden, London WC2N 4HSUK > > > > >> > @shapeblue > > > > >> > > > > > >> > > > > > >> > > > > > >> > > > > > >> > -----Original Message----- > > > > >> > From: Rafael Weingärtner [mailto:rafaelweingart...@gmail.com] > > > > >> > Sent: 20 February 2018 12:31 > > > > >> > To: dev <dev@cloudstack.apache.org> > > > > >> > Subject: Re: Caching modes > > > > >> > > > > > >> > This cache mode parameter does not exist in > > "CreateDiskOfferingCmd" > > > > >> > command. I also checked some commits from 2, 3, 4 and 5 years > ago, > > > and > > > > >> > this parameter was never there. If you check the API in [1], you > > can > > > > see > > > > >> > that it is not an expected parameter. Moreover, I do not see any > > use > > > > of > > > > >> > "setCacheMode" in the code (in case it is updated by some other > > > > method). > > > > >> > Interestingly enough, the code uses "getCacheMode". > > > > >> > > > > > >> > In summary, it is not a feature, and it does not work. It looks > > like > > > > >> some > > > > >> > leftover from dark ages when people could commit anything and > then > > > > they > > > > >> > would just leave a half implementation there in our code base. > > > > >> > > > > > >> > [1] > > > > >> > https://cloudstack.apache.org/api/apidocs-4.11/apis/ > > > > >> > createDiskOffering.html > > > > >> > > > > > >> > > > > > >> > On Tue, Feb 20, 2018 at 9:19 AM, Andrija Panic < > > > > andrija.pa...@gmail.com > > > > >> > > > > > >> > wrote: > > > > >> > > > > > >> > > I can also assume that "cachemode" as API parameter is not > > > > supported, > > > > >> > > since when creating data disk offering via GUI also doesn't > set > > it > > > > in > > > > >> > DB/table. > > > > >> > > > > > > >> > > CM: create diskoffering name=xxx displaytext=xxx > > > > storagetype=shared > > > > >> > > disksize=1024 cachemode=writeback > > > > >> > > > > > > >> > > this also does not set cachemode in table... my guess it's not > > > > >> > > implemented in API > > > > >> > > > > > > >> > > Let me know if I can help with any testing here. > > > > >> > > > > > > >> > > Cheers > > > > >> > > > > > > >> > > On 20 February 2018 at 13:09, Andrija Panic < > > > > andrija.pa...@gmail.com> > > > > >> > > wrote: > > > > >> > > > > > > >> > > > Hi Paul, > > > > >> > > > > > > > >> > > > not helping directly answering your question, but here are > > some > > > > >> > > > observations and "warning" if client's are using write-back > > > cache > > > > on > > > > >> > > > KVM level > > > > >> > > > > > > > >> > > > > > > > >> > > > I have (long time ago) tested performance in 3 combinations > > > (this > > > > >> > > > was not really thorough testing but a brief testing with FIO > > and > > > > >> > > > random IO WRITE) > > > > >> > > > > > > > >> > > > - just CEPH rbd cache (on KVM side) > > > > >> > > > i.e. [client] > > > > >> > > > rbd cache = true > > > > >> > > > rbd cache writethrough until flush = true > > > > >> > > > #(this is default 32MB per volume, afaik > > > > >> > > > > > > > >> > > > - just KMV write-back cache (had to manually edit > > disk_offering > > > > >> > > > table to activate cache mode, since when creating new disk > > > > offering > > > > >> > > > via GUI, the disk_offering tables was NOT populated with > > > > >> > > > "write-back" sertting/value > > > > >> > > ! ) > > > > >> > > > > > > > >> > > > - both CEPH and KVM write-back cahce active > > > > >> > > > > > > > >> > > > My observations were like following, but would be good to > > > actually > > > > >> > > confirm > > > > >> > > > by someone else: > > > > >> > > > > > > > >> > > > - same performance with only CEPH caching or with only KVM > > > caching > > > > >> > > > - a bit worse performance with both CEPH and KVM caching > > active > > > > >> > > > (nonsense combination, I know...) > > > > >> > > > > > > > >> > > > > > > > >> > > > Please keep in mind, that some ACS functionality, KVM > > > > >> > > > live-migrations on shared storage (NFS/CEPH) are NOT > supported > > > > when > > > > >> > > > you use KVM write-back cache, since this is considered > > "unsafe" > > > > >> > migration, more info here: > > > > >> > > > https://doc.opensuse.org/documentation/leap/virtualization/ > > > > >> > > html/book.virt/ > > > > >> > > > cha.cachemodes.html#sec.cache.mode.live.migration > > > > >> > > > > > > > >> > > > or in short: > > > > >> > > > " > > > > >> > > > The libvirt management layer includes checks for migration > > > > >> > > > compatibility based on several factors. If the guest storage > > is > > > > >> > > > hosted on a clustered file system, is read-only or is marked > > > > >> > > > shareable, then the cache mode is ignored when determining > if > > > > >> > > > migration can be allowed. Otherwise libvirt will not allow > > > > migration > > > > >> > > > unless the cache mode is set to none. However, this > > restriction > > > > can > > > > >> > > > be overridden with the “unsafe” option to the migration > APIs, > > > > which > > > > >> > > > is also supported by virsh, as for example in > > > > >> > > > > > > > >> > > > virsh migrate --live --unsafe > > > > >> > > > " > > > > >> > > > > > > > >> > > > Cheers > > > > >> > > > Andrija > > > > >> > > > > > > > >> > > > > > > > >> > > > On 20 February 2018 at 11:24, Paul Angus < > > > > paul.an...@shapeblue.com> > > > > >> > > wrote: > > > > >> > > > > > > > >> > > >> Hi Wido, > > > > >> > > >> > > > > >> > > >> This is for KVM (with Ceph backend as it happens), the API > > > > >> > > >> documentation is out of sync with UI capabilities, so I'm > > > trying > > > > to > > > > >> > > >> figure out if we > > > > >> > > >> *should* be able to set cacheMode for root disks. It seems > > to > > > > make > > > > >> > > quite a > > > > >> > > >> difference to performance. > > > > >> > > >> > > > > >> > > >> > > > > >> > > >> > > > > >> > > >> paul.an...@shapeblue.com > > > > >> > > >> www.shapeblue.com > > > > >> > > >> 53 Chandos Place, Covent Garden, London WC2N 4HSUK > > @shapeblue > > > > >> > > >> > > > > >> > > >> > > > > >> > > >> > > > > >> > > >> > > > > >> > > >> -----Original Message----- > > > > >> > > >> From: Wido den Hollander [mailto:w...@widodh.nl] > > > > >> > > >> Sent: 20 February 2018 09:03 > > > > >> > > >> To: dev@cloudstack.apache.org > > > > >> > > >> Subject: Re: Caching modes > > > > >> > > >> > > > > >> > > >> > > > > >> > > >> > > > > >> > > >> On 02/20/2018 09:46 AM, Paul Angus wrote: > > > > >> > > >> > Hey guys, > > > > >> > > >> > > > > > >> > > >> > Can anyone shed any light on write caching in CloudStack? > > > > >> > cacheMode > > > > >> > > >> is available through the UI for data disks (but not root > > > disks), > > > > >> but > > > > >> > not > > > > >> > > >> documented as an API option for data or root disks > (although > > is > > > > >> > > documented > > > > >> > > >> as a response for data disks). > > > > >> > > >> > > > > > >> > > >> > > > > >> > > >> What hypervisor? > > > > >> > > >> > > > > >> > > >> In case of KVM it's passed down to XML which then passes it > > to > > > > >> > Qemu/KVM > > > > >> > > >> which then handles the caching. > > > > >> > > >> > > > > >> > > >> The implementation varies per hypervisor, so that should be > > the > > > > >> > > question. > > > > >> > > >> > > > > >> > > >> Wido > > > > >> > > >> > > > > >> > > >> > > > > >> > > >> > #huh? > > > > >> > > >> > > > > > >> > > >> > thanks > > > > >> > > >> > > > > > >> > > >> > > > > > >> > > >> > > > > > >> > > >> > paul.an...@shapeblue.com > > > > >> > > >> > www.shapeblue.com > > > > >> > > >> > 53 Chandos Place, Covent Garden, London WC2N 4HSUK > > > @shapeblue > > > > >> > > >> > > > > > >> > > >> > > > > > >> > > >> > > > > > >> > > >> > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > -- > > > > >> > > > > > > > >> > > > Andrija Panić > > > > >> > > > > > > > >> > > > > > > >> > > > > > > >> > > > > > > >> > > -- > > > > >> > > > > > > >> > > Andrija Panić > > > > >> > > > > > > >> > > > > > >> > > > > > >> > > > > > >> > -- > > > > >> > Rafael Weingärtner > > > > >> > > > > > >> > > > > >> > > > > >> > > > > >> -- > > > > >> Rafael Weingärtner > > > > >> > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > Andrija Panić > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > Andrija Panić > > > > > > > > > > > > > > > > -- > > > Rafael Weingärtner > > > > > > > > > > > -- > > > > Andrija Panić > > > > > > -- > Rafael Weingärtner > -- Andrija Panić
