On Fri, 2016-01-22 at 14:56 -0600, NightLightHosts Admin wrote:
On Fri, Jan 22, 2016 at 11:02 AM, Ed Heron Ed@heron-ent.com wrote:
I'm still running CentOS 5 with Xen.
We recently replaced a virtual host system board with an Intel S1400FP4, so the host went from a 4 core Xeon with 32G RAM to a 6 core Xeon with 48G RAM, max 96G. The drives are SSD.
I was recently asked to move an InterBase server from Windows 7 to Windows Server. The database is 30G.
I'm speculating that if I put the database on a 35G virtual disk and mirror it to a 35G RAM disk, the speed of database access might improve.
I use local LVM for my virtual disks with DRBD on top to mirror the disk to a backup server.
If I change grub.conf to increase RAM disk size and increase host RAM, I could create a 35G RAM disk.
I'd modify rc.local to add pvcreate /dev/ramdisk vgextend vg /dev/ramdisk lvconvert -m 1 --corelog vg/lv_database /dev/ramdisk
Even with lv_database being 35G, it doesn't take long to activate the mirror.
I haven't decided where to put the commands to turn off the lvm mirror. lvconvert -m 0 vg/lv_database vgreduce vg /dev/ramdisk pvremove /dev/ramdisk
I haven't put this in real world use, yet.
On it's face, this might speed up database access. Would we expect it to speed up database access in real world use?
Should I document the process so others could know how to do this? I realize new documentation for CentOS 5 virtualization would be considered obsolete before I wrote it but I'm expecting to test CentOS 7 virtualization in the next few months and, when I am comfortable, I'd upgrade my 18 virtual hosts. I would update the documentation, at that time, as well.
I may not understand enough to understand what you are doing, you want to actively mirror this with LVM or?
Yes, in a test environment, I am mirroring a Logical Volume with a RAM disk to increase the perceived speed of the disk. I'm expecting to convert a live guest to this type of setup, this weekend.
I was asking 2 questions. 1. Should I expect a significant increase in speed in a real world environment? With enough RAM, a good caching system will eventually do a similar function. This is almost like pre-loading a cache. 2. Should I document the process for others? I'm using CentOS 5 now, which is on it's way out, but I would update the documentation to include CentOS 7 when I upgrade my servers.