Moving from dedicated. openVZ, KVM or stick with dedicated?

luispt

New Member
Aug 5, 2010
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0
1
Hello,

Atm i have about 9 dedicated servers ( xeon x3220 + 8G ram DDR 2 and 2x 500gb raid1 ) running shared hosting with cPanel. I'm about to change this servers to new boxes.

I'm thinking about migrating my customers from dedi to a vps. I will buy lets say 4 more powerfull servers ( with raid 10 / 10k RPM drives ) and create 8 or 9 vms. From a management point of view, and using a cluster with promox it will much better, as even allows live migration, for example if a have a problem in a node i can quicky migrate to another one.

However i dont know if i will loose stability and power if i migrate to a VPS. Whats your suggestion? I'd better keep with dedicated servers to have more power, or a few vps with 4 / 8gb of memory and a faster raid will give me more performance?

Regarding the technology, what will give more mor performance / security ( openvz or kvm )? This will be all linux servers for now.

For the record, i already have two servers running about 40 openvz vps.

Please share your opinions.

thanks
 
It is impossible to answer this accurately as you haven't indicated the resource profile of the existing hardware servers. In my experience if you have lots and lots of machines that aren't IO bound then yes, sure, they make ideal candidates for VMs.

*However*, even with virtio disk IO is still the slowest component. Don't get me wrong, all of my production, test, demo and development databases are running on either Windows 2008/SQL Server or Linux/Postgres KVMs :) For my needs the IO cost of virtualisation was easy to swallow, but there is a cost.

OpenVZ gets around this cost by not really virtualising IO.

The best thing to do is montor your existing hardware, see how busy they are in terms of CPU, network, memory and disk IO and then decide. If they are all contending for disk IO then virtualising them will ruin your week :)

I currently have 50 pretty light weight (KVM) machines running on 3 HP GL 380 servers with 24GB of RAM (each) - I could *easily* put them on two servers. The most I have ever seen the server's CPU is about 24% (in the Proxmox GUI). I happen to run using a SAN (8x300 15K SAS disk and 4x600 15K SAS disk, both RAID 10). Previously I ran 4x300GB 15 SAS disk in RAID 10 and the performance was more than good enough in either setup.

To be honest, the only way you will find out is get a machine, stick more VMs on there than you expect and then emulate more load than you expect and see what happens.

Go for it - you won't regret it :)

Col
 
Hello,

Thank you for your reply. What to you suggest to monitor the servers and get detailed information? Sure i can use top and cpanel reports, but is there anything else i can use to get accurate information?

Regarding IO, atm i use raid with 7200 drives, and in vm i will use 4x10k or 15k rpm raid 10.

Shared storage ( san, nas ) is something i would love to use, but i really dont know how to make it work ( iscsi setup etc ).

thanks for your help
 
Hello,

Thank you for your reply. What to you suggest to monitor the servers and get detailed information? Sure i can use top and cpanel reports, but is there anything else i can use to get accurate information?
Wow - talk about a question with a million answers :) I personally use zabbix to monitor the servers and puppet to configure the servers. If you have a lot of servers then zabbix and puppet are very valuable. Nagios is really the granddaddy of them all and I think a lot can be learnt from downloading it and working through the documentation to get a good understanding of how the rest of them work.


Regarding IO, atm i use raid with 7200 drives, and in vm i will use 4x10k or 15k rpm raid 10.
But don't be surprised if native -> RAID with 7.2K drives is faster than virtual -> RAID with 15K RPM drives. Virtual disk IO is pretty expensive.

Shared storage ( san, nas ) is something i would love to use, but i really dont know how to make it work ( iscsi setup etc ).
It is a doddle really. I use a HP low end SAN and connecting to it from Proxmox is trivial. If you want to stay open source then purchase a server with really fast NICs and a lots of disk arrays, stick as many small 15K RPM drives in (8x125GB is much better than 3x300GB - the more heads the better) and then install OpenFiler or FreeNAS. I have no experience with them but I have googled good results.

Once you have the SAN setup connecting via Proxmox is really a 2 or three click setup and is well documented on the wiki.

Also, this forum is *very* good for technical support. Focused questions (unlike your first post ;)) tend to get very good answers and there are some very knowledgeable (udo for one!) on here.
 
thanks for your help.

The IO problem also apply to openvz?
Hi,
it's one advantage of openvz that the io is fast.

If you have a chance go for sas-drives instead of sata (this will speed up your io), raid10 (like yatesco allready wrote) and a fast raid-controller (i have good experiences with areca, other prefer adaptec).

Udo
 
Hello,

So, openvz should be the best option, even if it isnt a total virtualization platform.

Regarding hardware, i'm thinking about this:

2x INTEL XEON SIXCORE L5640
24GB RAM DDR3
8x 300GB SAS 15k RPM Seagate Cheetah or 4x 600GB. What is best?
Atm i use adaptecs 5405 and 5805, but i should use one with BBU, correct? Maybe 5405z?

Its all this supported?

thanks in advance.
 
No idea if your motherboard and chipset is supported but for the disks, 8x300 is better than 4x600. And yes, a decent BBU is absolutely critical.

Also, stick some more RAM in there if you can - once you get bitten by this you will find loads more things to virtualise ;)
 
Ok, i have setup a few kvm vm's. openvz will not be an option since i need to add r1soft cdp installed, and openvz doesnt support it. I will need to install it per vm and kvm is the only option.

What worries me is the IO problem, as i cannot add sites and have slowness compared to dedicated servers. What is the best way to test this?

thanks for all your help, have been great.
 
pveperf /var/lib/vz and pveperf / are useful diagnostics on the host
also, iostat in the guest is quite useful....post those here.
 
I'm testing, and noticed that i cannot make live migrations of kvm vm's. I'm using raw format ( its the fastest, correct )?

Any way to move the vms live?
 
Hello,

I'm trying the disk type options, and really dont see any differences. For KVM guests running centos 5.5 x64 what would be the best ( ide, virtio, scsi )?

In image format what do you suggest ( raw, vmdk, qcow2 )?

thanks
 
Generally raw and virtio is the way to go. There are lots of posts about this, try searching (I don't mean that to sound as snarky as it does ;)).
 
Hello,

virtio + raw

[root@localhost ~]# dd if=/dev/zero of=/tmp/2G bs=1M count=2048; sync
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 11.1609 seconds, 192 MB/s
[root@localhost ~]# dd if=/dev/zero of=/tmp/2G bs=1M count=2048; sync
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 4.28411 seconds, 501 MB/s

[root@localhost ~]# dd if=/dev/zero of=/tmp/2G bs=1M count=2048; sync
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 2.29949 seconds, 934 MB/s


ide + raw

[root@localhost ~]# dd if=/dev/zero of=/tmp/2G bs=1M count=2048; sync
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 2.60447 seconds, 825 MB/s

[root@localhost ~]# dd if=/dev/zero of=/tmp/2G bs=1M count=2048; sync
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 2.50096 seconds, 859 MB/s

Is normal this diffrences in virtio? I really dont know what is the best option, as this will be mainly used to shared hosting.

thanks a lot
 
A couple of points ;)

- that is so quick it has to be cached. Try using a file bigger than your VM RAM (i.e. 10GB or something)
- secondly - the MBs doesn't include the sync. You want to do something like time 'dd if=/dev/zero of=/tmp/10G bs=1M count=10240; sync' (note the quotes)
 

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