storage response times

[RickPollock]

Has anyone done a test to determine at what point does storage response times affect a running guest?

Are there any recommendations from VMware storage read/write response times (optimal - maximum)?

[nonu]

Rick,

I am not sure about recommendations from Vmware about the Storage Response time and it varies due to various factors,but vmware have certain recommendations related to there VMFS file system and how we can maximize the use of physocal storage underlying it to get the maximum I/O performance for the virtualized servers.

Please got throught links provided below if you haven't and I feel that should help.

http://www.vmware.com/pdf/esx3_partition_align.pdf

http://blogs.vmware.com/vmtn/2006/12/keeping_up_with.html

http://www.vmware.com/technology/virtual-storage/best-practices.html

Thanks,

Nonu

[RickPollock]

Do you happen to know what MS recommends for a Boot from SAN Windows 2003 server? I found recommendations for SQL and Exchange, but not the O/S.

[kastlr]

I don't expect that you'll find such a documentation because ANY response time will affect a server, regardless of virtual or not.

And until you don't know the IO profile (Total IO's/sec, Read/Write Ratio, IO Block Size, random/sequentiell IO....) of your VM/Host, nobody could provide a clear answer.

But maybe the following documents does provide some answers.

Performance Characteristics of VMFS and RDM using a SAN (ESX 3.5)

http://www.vmware.com/files/pdf/performance_char_vmfs_rdm.pdf

Comparison of Storage Protocol Performance

http://www.vmware.com/files/pdf/storage_protocol_perf.pdf

[RickPollock]

I found this document useful. There are performance rules of thumb at the bottom...

[nonu]

Rick,

Regarding Boot from SAN,I guess it is Good option,but you need to be absolutely sure why you want to do that.

It is good for Exchange,I think I read it somewhere.But the question need to be assked is the What is the acceptable I/O performance for your Application owners..

We had lot of I/O performance issue in our Environment,with SQL and some of the other applications also.

Couple things which we have done are :-

1 Allign the v Disk with the base SAN volume so that I/O can be reduced.this helped in Improving performance by about 20-22%

2. Seperate the OS disk partition from the Application,so that I/O for both OS and let's say SQL are not going on same,

3. Addtionally one more thing which has helped in getting about 10% better performace is putting both disks on a Seperate Controller,Even though they are going on SAME Lun

All the things stated above are for things which are not boot form SAN.

It would be interesting to see how much difference it makes in term of I/O performance.

Thanks,

Nonu