Time settings/issues on ESXi 4.1

Here are some short and sweet items that i discovered yesterday;

Interestingly, ESXi does not allow you to change the timezone, it is permanently set to UTC.

Also, If you setup an NTP server on your ESXi hosts and that NTP server goes away for some reason, the ESXi host will not revert to using its’ own clock or even continuing to make a valient effort of keeping time, it instead reverts to January 1, 0001, to say this creates some issues is simplifying it.  The ESX hosts complain about not being able to “synchronize”, which is the first clue you get about the issue.  When you try and manually set the date through the VI-Client, you get a bunch of errors when you try and do anything and then the VI-Client froze.  The only option i found was to get that NTP server online.

Note: It may have been possible to do it via powershell or cli commands, however i had needed to get the NTP servers online anyway, and once this occurred, the ESXi servers re-synced and was able to respond.

“Save Location of VMDK” Bug in Virtual Center

So while doing a Proof of Concept test on a replication product for P2V, V2V and V2P scenarios a very interesting “bug” was encountered in Virtual Center that i’ve never encountered before.  We have to add .vmdk files that belong to VM “containers” to a “Master” VM.  So if you are protecting a SQL Server, you’ll have this “Master” VM’s .vmdk and the SQL VMs .vmdk attached to this VM.

The bug is this;

If you go and add another .vmdk to a VM, AFTER already choosing “attach an already existing vmdk” for a previously added vmdk, that new .vmdk will be created in the “already existing vmdk”s folder.

Since i’ve been working crazy hours, i’ll take a second to explain better.

So you have 2 VMs, they are named, “Master”, & “SQL”.  Each one is on a separate datastore in its’ own similarly named folder, which is default.  Then you go and add a 2nd vmdk to “Master” but choose to attach the vmdk from “SQL”.  Now you create another vmdk on the “Master”, however this is a new VMDK.  If you specify the location “store with the virtual machine”, it does not save the vmdk with the “Master” vmx, which is in the “Master” folder, instead it creates the new vmdk in the “SQL” folder.  This is quite interesting….

After digging around through the logs and doing some very quick testing, i found, what i believe, is the answer.  It seems that the “store with the virtual machine” is not actually returning with the location of the .vmx file, but actually returning with the location of last disk entry of the .vmx, so in this case “SQL”.

I would assume this is a simple fix by vmware, however since i have not encountered this before i’m wondering if i have just been lucky or if this is a new issue.

Why the 2TB Limit in ESX 4.1

So i was asked this question by a collegue of mine.  “Why is there still a 2TB size limit to a LUN in ESX”.   The argument was that in this day and age, and with ESX now running on a 64-bit kernel, why are we still ham-strung by this limitation?  After some consideration and thinking it was thought that maybe VMFS was the issue, but it can’t be because you can create extents and one big VMFS volume.

Well the answer is that ESX (& ESXi) are still using the SCSI-2 Standards. Yes the same SCSI-2 that was from ~1995.  The ultimate issue has to do with the way the standard addresses the “READ_CAPACITY” of the LUN.  It uses a 10-byte call for the capacity, which limits the return to a 32-bit number. (It actually is just under a 32-bit number, the last value of 0xffffffff is acutally reserved, and thus can’t be used.  This limits you to 2199023255040 bytes, which is just under the 2TB limit.

The only current work-around is extents, which are much less then ideal.

So until VMware decides to update their outdated storage methodology, we’re stuck with the 2TB limit.

Lack of Posts

Well i know i was supossed to start writing more, but things have been nuts between rebuilding our lab at work and my home life i haven’t had time.

I’m going to list my upcoming topics so that maybe i actually remember to write them….

iSCSI vs NFS Testing results on ESX 4.1

Discovery of correlation between vCPU count and VMFS write speed

Properly enabling iSCSI and connecting targets in RHEL 5

DataDomain and BOOST

My PrivateCloud Lab

Discovered issues with vCenter as a VM and running dvSwitches

Creating a 24TB Storage server for $5,000


So one of the recent tasks given to me was to create a “JBOD” Server for various uses.  I had to price it around $5k, be at least 20TB usable, and it had to be flexible, yet fast.  So i started doing some research into the subject.  What i came up with was that there was no way we could purchase a “pre-built” solution, of that size, for the price point we wanted.  The only remaining option was to build it myself using commodity hardware.


I had orginally spec’d out this server with much nicer hardware, or at least slightly nicer, however due to corporate policy, i had to use CDW….yay.  So some items are not ideal, such as the Motherboard and Power Supply, i happened to like a Gigabyte board and a Corsair PSU.  I will not list prices, as i’m sure by the time anybody reads this, they won’t be relevant.

ASUS M4A785-M  Motherboard,
AMD Phenom II X4 3.0ghz Quad-Core Processor,
Crucial 4gb DDR2 Kit, (Later i added an additional pair of 1gb RAM sticks i had laying around),
Antec 1000W Quattro Power Supply,
NORCO RPC-4020 4U Rackmount Server Case,
Areca ARC-1280ML PCIe SATA II RAID Controller Card,
Seagate Barracude 7.2kRPM 1.5TB 32MB Cache SATA HDD,  (20 of them)
A few Molex “Y” cables and extenders.
Any NICs you would like to add.
1GB USB Key (For the OpenFiler Install)

Operating System

The first decision was what operating system to run on this server.  After weighing my decisions it came down to “FreeNAS”, “OpenFiler”, “OpenSolaris w/ ZFS” or “Native Linux”.  Since there were time constraints on this project i did not have the time to really learn “OpenSolaris”.  I also thought that a full blown linux kernel would be a good choice, but may not provide the performance i needed, and that a “storage optimized” specialized kernel is the better route.  I ended up choosing “OpenFiler” since the community-at-large seemed to feel that OpenFiler performed better and had much better support for iSCSI which is something i wanted to test.  I also decided that i wanted to maximize space on my RAID array so i wanted to run the OpenFiler OS from a separate disk.  The original plan was to use a space 2.5″ HDD i had lying around, however the drive turned out to be no good.  So i opted to use a 2gb USB stick i had.  The OS does not have any read/write intensive tasks once it is loaded so USB 2.0 speeds should not be an issue.  The only time this may be an issue is if a lot of swapping is happening, and then there are other problems that need to be addressed first.

Installation and Configuration

The first step was to assemble the chassis.  The NORCO case came pretty much ready to go, i am actually quite impressed with this case.  It came with all the drive trays, the backplane for the drives, all the case fans and more then enough hardware for any installation.  The drives all came in OEM packaging, they were then secured into the hot-swap trays.  The motherboard, memory, CPU and Power Supply were all installed in the case.  The next thing to go in was the Areca controller.  This unfortunately took up my 16x PCI-E slot, as it requires an 8x PCI-E slot.  Thankfully many motherboards come with on-board video.  (Make sure the one you choose does, no sense eating up a PCI Slot for a video card)

The next item was to run the Molex Power cables.  This case powers the drives off the backplane, so you need to plug two molex plugs per backplane “strip”.  If you have large hands stop right now and enlist the help of somebody who is small-handed, as this is a really tight space.  You may have to use some Y-Cables and/or extenders depending on your supply and how many Molex ends it has.  (Note: Make sure that you try and balance out the Power Rails on your supply, so one with multiple rails as apposed to one large one seems to work better.)

Next is the SATA cables.  Theses should be supplied with the Areca Controller.  While this is no where near as bad as the Molex cables, this still isn’t fun.  The controller i used had Multi-lane SATA to 4-port SATA as well as a connecter that would normally light up little LED’s for Power/Activity lights. This extra connector isn’t necessary with the NORCO case, as the backplane actually handles the blinky lights.

At this point i would test out the system, make sure it at least POSTS’ as well as detects all the hardware correctly.  Next i had to create the RAID Arrays.  Initially the design called for 3 RAID-5 Arrays consisting of 7,7, & 6 disks.  (Note: With this array if you can choose to do the initialization now or in the background.  Now took well over a weekend to perform due to the size of the server.)

After that i inserted the USB stick and the OpenFiler Install CD.  Boot to the CD and follow all the prompts to install the OS.  Make sure to install it to the USB stick and not any of the Arrays.  From there follow the OpenFiler documentation, if you paid for it, or use the various forums or other methods to configure it.  It is fairly straight-forward and pretty easy to use.

Performance Results

After everything was configured and setup i decided to do some simple tests to determine if the array was performing well and that things worked as they should.  Since OpenFiler runs a variant of Linux (rPath), i decided a simple dd read/write test would at least give me some ballpark numbers.

I did two tests on the local commandline,   “dd if=/dev/zero of=file bs=1024k count=20000” & “dd if=file of=/dev/null bs=1024k count=20000”.  This gave me sequential reads and writes totaling around 20gb, which made sure i was not just working in cache.

The tests gave me read speeds of anywhere from 300-500 MB/s, and write speads from 200-400 MB/s, yes thats Bytes.  I was quite impressed, especially since it was only running the test against a single RAID group, which is max of 7 disks.

The JBOD has been running as primary storage for my ESX lab.  It is hosting 12 ESX Servers and running around 80-90 VMs, over iSCSI.  It is now starting to see bad performance numbers, while the disk is being utilized fairly heavy

Unfortunately, since this is a Network-Disk box the major limitation has been the gigabit ports out of the back.

Lessons Learned

If i had to do this project over with what i know now, i would have done a few things differently.

1. Not settled on hardware and tried harder to get what i originally spec’d out.

This would have made my life much easier as i found out that this ASUS MB didn’t have the necessary PCI-E slots to put the quad-port GIG-E nics i wanted, as well as the iSCSI and FC HBA’s.

2. I would have going with OpenSolaris and ZFS or some other high performing FileSystem.

OpenFiler works quite well, but it has had some odd quirks, most notibly with NFS and it dropping the connections to ESX and not allowing them back in.

3. I would not have used iSCSI for the primary ESX Storage.

In all of our testing it was seen that NFS VMFS volumes out performed iSCSI VMFS volumes.

4. 10gb

1gb pipes just weren’t fast enough for what we were trying to do.