| W. Chris Shank on 15 Sep 2007 20:24:06 -0000 |
|
I am thinking about that. I my concern is I'd have trouble moving VMs between hosts and this is an option I'd like to keep open. Or would a simple dd allow a move between VMs? Currently, I'm testing I/O using a 2 x 500Gb SATA mirror sliced into 6 partitions. I've got 4 identical VMs running across 2 cores. I did a simple test dd if=/dev/zero of=bigfile - individually each VM can do this operation at ~22 MB/s. If I have all 4 do this at the same time they each go between 5-7 MB/s. The VMs are slow to respond but only be a few seconds. On my other system, the other VMs become unusable if one has excessive I/O. I have one partition that I'm going to attempt to use in RAM mode and see how the disk access is on that for comparison. ----- Original Message ----- From: Matt Mossholder <matt@mossholder.com> To: Philadelphia Linux User's Group Discussion List <plug@lists.phillylinux.org> Sent: Friday, September 14, 2007 5:16:08 PM GMT-0500 Subject: Re: [PLUG] help me design my server You might want to consider using raw volumes, rather than files on the host. Not only is it more space efficient, it should help with reducing your disk I/O. --Matt On Fri, 2007-09-14 at 12:43 -0400, W. Chris Shank wrote: > The VMs use disk files on the host filesystem. So the host talks to > the SATA controller directly. > > > ----- Original Message ----- > From: John Von Essen <john@essenz.com> > To: Philadelphia Linux User's Group Discussion List > <plug@lists.phillylinux.org> > Sent: Friday, September 14, 2007 12:17:10 PM GMT-0500 > Subject: Re: [PLUG] help me design my server > > How does the VM access the storage? > > > Not sure which kernel context talks to the SATA controller. But > whichever kernel does that, thats the one that needs more ram so it > can do caching on the IO requests being sent to the controller. > > > -John > > On Sep 14, 2007, at 11:41 AM, W. Chris Shank wrote: > > I'm going to do that - but there isn't really any swapping on > the host OS. Or are you saying more virtual RAM on the VM? > > > ----- Original Message ----- > From: John Von Essen <john@essenz.com> > To: Philadelphia Linux User's Group Discussion List > <plug@lists.phillylinux.org> > Sent: Friday, September 14, 2007 11:32:13 AM GMT-0500 > Subject: Re: [PLUG] help me design my server > > Forget to mention, increasing RAM will make a significant > difference. The kernel caching will alleviate alot of disk IO > since those requests will be processed right from cache. > Performance of increased memory is somewhat dependent on how > you use your disk, i.e. heavy reads of common data vs random > data. > > > -John > > > > > > On Sep 14, 2007, at 11:28 AM, John Von Essen wrote: > > Chris, > > > The SATA arrays will always poor IO performance in > environments like yours. I have some experience from > going through issues with an 8-core Postgres server > with heavy disk IO problems. > > > SCSI Raid will be better, especially if you have alot > of spindles. Raid 10 instead of Raid 5 etc.,. And if > you split it up across both channels of a dual channel > card or spit it across multiple cards, that will help > too. Problem is size limitations of SCSI raid 10 due > to the numbers of drive slots in most external > enclusores. 14-bay enclosure with Raid 10 and 146Gb > drives will give about 1Tb. I wouldn't recommend using > the 300Gb scsi drives. Smaller the drive, the better. > > > Eventually, SCSI will also break down. When that > happens, you'll start to need a Fibre-Channel attached > SAN, one specifically designed for high IO > environments. The EMC Clarrions are getting a little > better in price, but still pricy when compared to SATA > arrays. > > > You may never need the EMC-level performance, so SCSI > Raid with alot of spindles and good HBA controller > management might do the trick for awhile. > > > -John > > On Sep 14, 2007, at 10:50 AM, W. Chris Shank wrote: > > I need to spec-out and architect another > VMWare and/or Xen VM host server. Currently I > have one with 8 cores, 4GB ram, and 1.5TB HDD > as 4 500GB SATA with hardware raid5. We are > starting to hit the wall with this setup > running 5 VMs on it. Particularly, it seems > the HDD I/O is the bottleneck. If one VM hits > the disks hard it makes the others pretty much > useless. > > So I have a budget to get another honking > server. I'm confident the quad-core Xeons with > the vm extensions are sufficient. I'll go > ahead and bump the RAM to 16G too. The area > I'm most concerned with is the disk I/O. I'm > thinking that instead of one big RAID5, I'll > pair smaller drives - so i'll have 4 sets of 2 > 250G SATA mirrors. Then direct it so that 2-3 > VMs are on each raid. Or should I go SCSI and > keep one large RAID5? > > So if you had the $$, what would you get and > how would you configure it. > > Thanks > > -- > W. Chris Shank > ACE Technology Group, LLC > www.myremoteITdept.com > (610) 640-4223 > > -------------------------------- > Security Note: To protect against computer viruses, > e-mail programs may prevent sending or receiving > certain types of file attachments. Check your e-mail > security settings to determine how attachments are > handled. > ___________________________________________________________________________ > Philadelphia Linux Users Group -- > http://www.phillylinux.org > Announcements - > http://lists.phillylinux.org/mailman/listinfo/plug-announce > General Discussion -- > http://lists.phillylinux.org/mailman/listinfo/plug > > John Von Essen (john@essenz.com) > President, Essenz Consulting www.essenz.com > > > > > > > > > ___________________________________________________________________________ > Philadelphia Linux Users Group -- > http://www.phillylinux.org > Announcements - > http://lists.phillylinux.org/mailman/listinfo/plug-announce > General Discussion -- > http://lists.phillylinux.org/mailman/listinfo/plug > > John Von Essen (john@essenz.com) > President, Essenz Consulting www.essenz.com > > > > > > > > > > > -- > W. Chris Shank > ACE Technology Group, LLC > www.myremoteITdept.com > (610) 640-4223 > > -------------------------------- > Security Note: To protect against computer viruses, > e-mail programs may prevent sending or receiving > certain types of file attachments. Check your e-mail > security settings to determine how attachments are > handled. > ___________________________________________________________________________ > Philadelphia Linux Users Group -- > http://www.phillylinux.org > Announcements - > http://lists.phillylinux.org/mailman/listinfo/plug-announce > General Discussion -- > http://lists.phillylinux.org/mailman/listinfo/plug > > John Von Essen (john@essenz.com) > > President, Essenz Consulting www.essenz.com > > > > > > > > > > -- > W. Chris Shank > ACE Technology Group, LLC > www.myremoteITdept.com > (610) 640-4223 > > -------------------------------- > Security Note: To protect against computer viruses, > e-mail programs may prevent sending or receiving > certain types of file attachments. Check your e-mail > security settings to determine how attachments are > handled. > ___________________________________________________________________________ > Philadelphia Linux Users Group -- http://www.phillylinux.org > Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce > General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug ___________________________________________________________________________ Philadelphia Linux Users Group -- http://www.phillylinux.org Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug -- W. Chris Shank ACE Technology Group, LLC www.myremoteITdept.com (610) 640-4223 -------------------------------- Security Note: To protect against computer viruses, e-mail programs may prevent sending or receiving certain types of file attachments. Check your e-mail security settings to determine how attachments are handled. ___________________________________________________________________________ Philadelphia Linux Users Group -- http://www.phillylinux.org Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug
|
|