Hi all, I have installed FreeBSD 8.3 amd64 release in an ESXi server. Due to some limitations, I can only assign 2GiB of RAM to this virtual machine and I need to use ZFS as filesystem to store some data (MySQL databases). According to http://wiki.freebsd.org/ZFSTuningGuide I have configured some options: vfs.zfs.write_limit_override=268435456 kern.maxvnodes=250000 According to ZFS version, FreeBSD 8,3 comes with version 28, and reading previous guide there is not need to adjust nothing more. But what about l2arc options?? Do I need to adjust vfs.zfs.arc_max and vm.kmem_size options?? How can I calculate these values?? Thanks. -- CL Martinez carlopmart {at} gmail {d0t} com
On 04/16/2012 07:10 PM, Chuck Swiger wrote:> On Apr 16, 2012, at 9:57 AM, carlopmart wrote: >> I have installed FreeBSD 8.3 amd64 release in an ESXi server. Due to some limitations, I can only assign 2GiB of RAM to this virtual machine and I need to use ZFS as filesystem to store some data (MySQL databases). > > That combination doesn't make much sense, frankly. > > ZFS is very memory hungry-- I wouldn't want to run it on anything with less than 4GB of RAM, although other folks around here have reported successful setups under 2GB of RAM with some tuning. However, the data integrity benefits of ZFS mostly come from it talking directly to disks in JBOD configuration; if ZFS is just running in a VM and talking to a filesystem image, it loses much of the advantage which it might otherwise provide. > > You'd almost certainly get better MySQL performance by going with UFSv2 and having the DB use most of the RAM, instead of having it be sucked away by ZFS. > > Regards,Thanks Chuck. Yes, I know it is not hte best option. But I need to tunning this vm with ZFS. Almost, is the minimum RAM needed for ZFS according to http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/filesystems-zfs.html. -- CL Martinez carlopmart {at} gmail {d0t} com
On Apr 16, 2012, at 9:57 AM, carlopmart wrote:> I have installed FreeBSD 8.3 amd64 release in an ESXi server. Due to some limitations, I can only assign 2GiB of RAM to this virtual machine and I need to use ZFS as filesystem to store some data (MySQL databases).That combination doesn't make much sense, frankly. ZFS is very memory hungry-- I wouldn't want to run it on anything with less than 4GB of RAM, although other folks around here have reported successful setups under 2GB of RAM with some tuning. However, the data integrity benefits of ZFS mostly come from it talking directly to disks in JBOD configuration; if ZFS is just running in a VM and talking to a filesystem image, it loses much of the advantage which it might otherwise provide. You'd almost certainly get better MySQL performance by going with UFSv2 and having the DB use most of the RAM, instead of having it be sucked away by ZFS. Regards, -- -Chuck
On Mon, Apr 16, 2012 at 06:57:45PM +0200, carlopmart wrote:> I have installed FreeBSD 8.3 amd64 release in an ESXi server. Due to > some limitations, I can only assign 2GiB of RAM to this virtual machine > and I need to use ZFS as filesystem to store some data (MySQL databases). > > According to http://wiki.freebsd.org/ZFSTuningGuide I have configured > some options: > > vfs.zfs.write_limit_override=268435456 > kern.maxvnodes=250000 > > According to ZFS version, FreeBSD 8,3 comes with version 28, and > reading previous guide there is not need to adjust nothing more.I am boot 9.0 inside ESXi with 256MB RAM. And pass buildworld. /boot/loader.conf: vm.kmem_size="512M" vfs.zfs.txg.timeout="5" vfs.zfs.vdev.cache.size="4M" vfs.zfs.arc_max="16M"> But what about l2arc options?? Do I need to adjust vfs.zfs.arc_max and > vm.kmem_size options?? How can I calculate these values??vm.kmem_size must be >512M. kernel don't allow to setup vm.kmem_size to more the 2*RAM. zfs don't allow to setup vfs.zfs.arc_max < max(RAM/32, 16MB).