Virtualization

VMware vSphere 4 Thin Provisioning: Pros & Cons

by

vSphere 4’s thin provisioning is a pretty cool feature, but it has downsides, too. I was putting together a concise list of pros & cons for a customer, and I thought I’d share (especially given all the thin provisioning talk lately). Please leave me a comment if I’ve missed something. Pros: Saves disk space where it isn’t really being used by permitting overcommitment, meaning: more VMs per datastore, which, for local datastores, means more VMs per host. better utilization of expensive storage. Smaller disk allocations translate into faster storage VMotions, clones, snapshot operations. You are only copying what needs to be copied. Incredibly easy to convert to and from thin-provisioned disks, on the fly, using Storage VMotion. More flexible disk …

Read More

vCheck 3

by

I second what Duncan Epping said about Alan Renouf and his vCheck 3 script. In fact, I was in the middle of writing a very similar post when I saw his. I won’t duplicate what Duncan said, but I will say: 1. If you haven’t started using PowerCLI to help manage your infrastructure you might want to check it out. I started using it when I was doing mass Storage VMotions and got sick of doing it all through the vSphere client. Turns out, in PowerCLI, it’s: Get-Datastore “source-datastore” | Get-VM | Move-VM -datastore (Get-Datastore “target-datastore”) …and then you wait for it to finish. That’s really slick. 2. I don’t pick up a new tool on a whim. I always …

Read More

ALUA Rocks

by

Ack, I was seconds away from writing the same post as Nick Triantos on Upgrading from non-ALUA to ALUA, as I’ve spent the afternoon so far doing this and documenting the process. The process works great, and it didn’t disrupt my clusters at all. The only things I did differently were: 1. I issued the “/usr/sbin/esxcli nmp satp setdefaultpsp –psp VMW_PSP_RR –satp VMW_SATP_ALUA” command on all the hosts prior to rebooting them. 2. I was able to combine this work with the application of the ESX 4.0 patch for the RAID controller cache problems, so Update Manager took care of all the rebooting for me. It does feel good to be lazy some days. If you have a NetApp array …

Read More

VMware & Linux Hot-Add Disks

by

Did you know you can add new virtual hard disks to a running Linux VMware VM, and they can be visible to the OS without a reboot? First, add a new hard disk the way you’d normally do it (Edit Settings -> etc.). Add it to the existing virtual SCSI adapter (don’t create a new one). Then, use a script like Kurt Garloff’s rescan-scsi-bus.sh to pick up the new device. If you’re using the Linux Logical Volume Manager you can partition the new device, run pvcreate, add it to a volume group, and grow a filesystem with ext2online/resize2fs (RHEL 4/5), all without the end users noticing. Just don’t forget to align the partitions on the new device before you use …

Read More

Tell Your Purchasing People: IPv6, VMware

by

In the world of system administration there aren’t too many things that are black & white. Everything is a shade of gray where admins solve their own problems however they need to, bending to the local desires & needs of their users or management. Everybody is right, nobody is wrong. I’ve come to realize that, and it’s no big deal. I am convinced, however, that if your organization does not have “fully implemented IPv6 support” and “full support under VMware virtual infrastructure” as requirements for purchasing any new hardware, software, or services, you’re doing it wrong[1][2]. Let’s assume that anything you’re buying now will last 5+ years. In 5+ years we will be out of IPv4 address space[3]. And it …

Read More

Host CPU is Incompatible…

by

I now have a cluster of ESX 4.0 hosts running with EVC enabled, in “Intel Xeon Core 2” mode. It’s been working okay so far (there are some rough edges here and there, nothing showstopping) and this morning I decided to convert a couple of my VMs to the new ESX 4 hardware format, “VM Version 7.” As soon as I upgraded the virtual hardware the VMs in question stopped being able to VMotion at all giving me the error: “Host CPU is incompatible with the virtual machine’s requirements at CPUID level 0x1 register ‘ecx’.” no matter where I tried to VMotion it to (even the same CPUs on a different machine). Not cool. These were VMs that were working …

Read More

VMworld 2009

by

Heck yeah, I was approved to go to VMworld 2009 today. In case you’re still trying to convince someone you should go, here’s the approach that has worked for me for the last three years, amidst constant budget problems and skepticism about virtual environments: 1. VMworld is the best opportunity & best value for VMware software training in the United States during the year. There are hundreds of sessions, labs, and other hands-on opportunities. You’ll learn better ways to do what you’re already doing, good ways to start doing things you want to do (like implementing vSphere 4, SRM, Lab Manager, View, etc.), and be able to talk to people who are already doing it to find out how well …

Read More

Disabling the Hardware Prefetcher on Dell R900s

by

One of my favorite places to glean tuning tips, especially obscure ones, is from SPECint or VMmark notes and disclosures. I have a number of Dell R900s in my virtual infrastructure, so I perused the Dell R900 VMmark results the other day. The notes show that the testers had disabled the Hardware Prefetcher and the Adjacent Sector Prefetch in the BIOS. I didn’t know much about the Hardware Prefetcher or the Adjacent Sector Prefetch, so I started poking around. Dell doesn’t have much information about these features but IBM does, and since it’s an Intel processor feature the descriptions should be mostly accurate across vendors. The IBM xSeries 366 tuning tips have a nice blurb about the hardware prefetcher: By …

Read More

Size Labels for Virtual Environments – A Proposal

by

“How big is your virtual environment?” I love that question. Find a virtual environment and ask ten people who work on it, and they’ll give you ten different answers. “It’s pretty big,” one person will say. The next person will say “oh, we’re small.” The next two people asked will argue with each other until you shake your head and walk away. It’s all relative, too. If most guys you know have 50 virtual machines, and you have 200, you’re big, relatively-speaking. You’ve got problems they don’t have, and you’d probably like to talk with others that have had those same problems. Talking to a guy who has 2000 VMs isn’t going to help you much, though. He’s operating at …

Read More

Should I Use Fibre Channel or iSCSI?

by

Yet another frequently asked question: My company is getting more serious about virtualization. Should we keep using our fibre channel SAN or switch to iSCSI or NFS? My usual answer is a series of questions: What technology do you know best? How big is your SAN? Why are you thinking about switching? What’s your performance like? What will it cost? The thing is, I never have an answer. Whereas some common virtualization questions have easy answers this one depends heavily on what you’re trying to do. iSCSI is a great way for small- and medium-sized organizations to get into cluster filesystems. With 10 Gbps Ethernet you can get SAN-like performance, too, but 10 Gbps NICs are as costly as fibre …

Read More

+ More Posts +