On Mon, Feb 2, 2015 at 7:45 PM, Tomasz Chmielewski <man...@wpkg.org> wrote:
> On 2015-02-02 21:37, Fajar A. Nugraha wrote: > > It's certainly possible to do "not applicable" kinds of things with >>> processes and their page cache, i.e.: >>> >>> https://code.google.com/p/pagecache-mangagement/ [1] >>> >>> Or here, disabling O_DIRECT and sync would be sort of matching >>> "feature-wise" with KVM's cache=writeback: >>> >>> http://www.mcgill.org.za/stuff/software/nosync [2] >>> >>> Is it possible to set things like this for all processes in a given >>> lxc container? >>> >> >> What are you trying to achieve? >> > > I'm trying to achieve the equivalent of KVM's cache=writeback (or, > "libeatmydata / nosync") for the whole container. > > What I meant was, what are you trying to achieve by doing that? The ones you mentioned are ways to do something, which might not be applicable in this case. I assume you want to "disable sync completely, even if it means losing data on power failure" (which is what eatmydata does). > > If you want to disable sync for the container, the best you can do is >> probably use some filesystem that can do so. For example, zfs has >> "sync=disabled" per-dataset settings. So you can have "sync=standard" >> for filesystems used by the host, and "sync=disabled" for filesystems >> used by containers. >> > > That's a weird advice, given that lxc are Linux containers, and ZFS is not > in Linux kernel (I know that there are some 3rd party porting attempts, but > it's not really applicable in many situations). > > Honestly, that's the best advice I can give. It's straightforward, simple, and works. There are lots of zfsonlinux users using it on production environment. Even lxc-create supports zfs as backingstore, to a degree (man lxc-create). And doing the above is the equivalent of having eatmydata running on everything that access that dataset. Other possible solutions that I know of either does not work (e.g. eatmydata lxc-start ...) or adds additional layers and complexity (e.g. using an additional layer like iscsi/scst and setting nv_cache=1 on scst) -- Fajar
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