profile for Gajendra D Ambi on Stack Exchange, a network of free, community-driven Q&A sites

Tuesday, July 17, 2012

Unable to power on VM of VMware because the disk is full

Issue : Unable to power on the VM because the c drive is full or the disk/datastore is (thin) over provisioned.
Resolution : Reduce the memory allocated to the VM to free up some space since the reduction in the memory will result in the reduction of pagefile/vswp size and the reduction in the vmdk. Once you are able to power on the VM then make sure you  free up some more space and increase the size/partition of the C drive by using the vmwareKB/1007266

Friday, July 13, 2012

ESXi 4.x / 5.x lun bigger than 2tb grayed out

Issue: A 4tb lun which was working fine with a VM running in it, is grayed out. The Virtual Machine(s) is/are working fine in it but the lun itself seems to be not responding.

Cause: The cluster has both esxi 4.x and 5.x hosts and 4.x hosts cannot handle or see luns larger than 2tb-512kb where as 5.x hosts can handle luns of the size of upto 64tb. This causes a conflict of interest among the hosts for the lun > 2tb and thus it becomes grayed out.

Resolution :  Luckily the VM which was running in that lun was running on 5.x host and if it was running in 4.x host then the first thing to do is to vmotion the vm to a host of 4.x; then unpresent the lun from the storage to all the 4.x host and do a rescan for datastores for the cluster (right click on the cluster>scan for datastores).

Monday, July 2, 2012

Formula to calculate Disk throughput, IOPS, MBps and vice versa

couldnt resist borrowing from Dean's Blog

IOPS = Throughput/IO               (all value in kb)
IOPS=[MB/KB]*1024 or
IOPS = (MBps Throughput / KB per IO) * 1024 [since 1mb=1024kb]
So here is the calculation I was using:
So using the above, if I wanted to configure an IOPS limit to satisfy a 10 MBps throughput using a 8KB IO request size I would require to set the SIOC IOPS limit to 1280.
First let us convert 10MBps to kbps
IOPS = (10240/8)
= 1280
It is possible to use the calculation in reverse to determine the MBps required to achieve the  IOPS claim using the following:
MBps = (IOPS * KB per IO) /1024 
In the above example where the requirement is to achieve 1280 IOPS, we would need a throughput of 10MBps to satisfy that claim.
MBps = (1280 * 8) /1024 = 10
  • Typically when your workloads are read intensive it is best to use RAID 5 or RAID 6. When the workload is write intensive you want to use RAID 1 or RAID 1+0. Hopefully the application owner can give you the read/write percentages so that you can determine which RAID level is best.
  • Here’s an example:
        • Formula: (total required IOPs * read%) + (total required IOPs * write% * RAID penalty) = total IOPs required
        • 400 IOPs required
        • 35% read
        • 65% write
      • RAID1 = (400 * 0.35) + (400 * 0.65 * 2) = 660 IOPs
        • 15K disks required = 4
        • 10K disks required = 5
        • 7.2 disks required =  9
      • RAID5 = (400 * 0.35) + (400 * 0.65 * 4) =  1180 IOPs
        • 15K disks required = 7
        • 10K disks required = 9
        • 7.2 disks required =  16
      • RAID6 = (400 * 0.35) + (400 * 0.65 * 6) = 1700 IOPs
        • 15K disks required = 10
        • 10K disks required = 14
        7.2 disks required =  23 

RPM(rotations per minute) speed

Write Penalty

(TOTAL IOps × % READ)+ [(TOTAL IOps × % WRITE) ×RAID Penalty]=Total IOPS Required
IOPS Required= IOPS*(Read%)+IOPS*write%*Raid Penalty

BIOS for VMware Workstation 8 VMs

Issue: How to enter the BIOS of the VMs in VMware workstation 8.
Add bios.bootDelay = "5000" to config.ini at
c:\programdata\vmware\vmware workstation and you will get time to enter the BIOS screen for all the VMs.
If you want it for your vcenter VMs then you might want to edit