This question is two fold.  Part 1:  Is it a bad idea to virtualize a storage solution and run VMDKs off of that as opposed to the original VMFS datastore.  Essentially lets assume I have 2 TB worth of RAID'd DAS.  Currently I have a few VMDKs on the DAS VMSFS.  What I want to do is remove the VMDKs off the VMFS, allocate a good 1.8-1.9TB for a FreeNAS installation (a big FreeNAS VMDK), and run the other VMDKs off of that via NFS.  I don't have the hardware for a NAS but have a bunch of different shares.  This would simplify my management.  I understand there is some overhead with another layer of storage abstraction (A virtual ZFS file system over NFS backed by RAID'd DAS formatted as VMFS) but I don't see how it could be too bad.  The NAS also has more features than a simple VMFS datastore on DAS.  Part 2:  VMWare frowns on long running snapshots, but what about ZFS snapshots?  Is it safe\recomended to run my guest VMDKs (Windows clients, random servers) on ZFS snapshots?  This will give me the ability to quickly rollback VMs to earlier states without the implications of long running snapshots directly on the VMFS.
I'm still new to ZFS. I've been using Nexenta but I'm thinking of switching to OpenIndiana or Solaris 11 Express. Right now, I'm at a point of considering virtualizing the ZFS server as a guest within either ESXi, Hyper-V or XenServer (I haven't decided which one yet - I'm leaning towards ESXi for VMDirectPath and FreeBSD support).   The primary reason being that it seems like I have enough resources to go around that I could easily have 1-3 other VMs running concurrently. Mostly Windows Server. Maybe a Linux/BSD VM as well. I'd like the virtualized ZFS server to host all the data for the other VMs so their data could be kept on a physically separate disks from the ZFS disks (mount as iscsi or nfs).  The server currently has an AMD Phenom II with 6 total cores (2 unlocked), 16GB RAM (maxed out) and an LSI SAS 1068E HBA with (7) 1TB SATA II disks attached (planning on RAIDZ2 with hot spare). I also have (4) 32GB SATA II SSDs attached to the motherboard. I'm hoping to mirror two of the SSDs to a boot mirror (for the virtual host), and leave the other two SSDs for ZIL and L2ARC (for the ZFS VM guest). I'm willing to add two more disks to store the VM guests and allocate all seven of the current disks as ZFS storage. Note: The motherboard does not have IOMMU support as the 880G doesn't support it, but I do have an 890FX board which does have IOMMU if it makes a huge difference.  My questions are:  1) Is it wise to do this? I don't see any obviously downside (which makes me wonder why no one else has mentioned it). I feel like I could be making a huge oversight and I'd hate to commit to this, move over all my data only to go fubar from some minute detail I missed.  2) ZFS virtual guest performance? I'm willing to take a small performance hit but I'd think if the VM guest has full disk access to the disks that at the very least, disk I/O performance will be negligible (in comparison to running ZFS non-virtualized). Can anyone speak to this from experience hosting a ZFS server as a VM guest?
Add and remove update channels in an easy terminal way I know there is a GUI in Ubuntu Software &amp; Updates to enable the update channels   updates proposed backports security   as shown in this screenshot:    I am looking for an easy way to do this from within a terminal using commands such as    sudo apt-add-update enable updates sudo apt-add-update enable proposed sudo apt-add-update enable backports sudo apt-add-update enable security  sudo apt-add-update disable updates sudo apt-add-update disable proposed sudo apt-add-update disable backports sudo apt-add-update disable security   and an additional thing  sudo apt-add-update enable default  sudo apt-add-update disable default     Some examples for a better understanding   An empty sources.list   cat /etc/apt/sources.list  &lt;empty&gt;  sudo apt-add-update enable security  &lt;empty&gt;   One enabled repository (main)   cat /etc/apt/sources.list  deb http://archive.ubuntu.com/ubuntu wily main  sudo apt-add-update enable security  deb http://archive.ubuntu.com/ubuntu wily main deb http://archive.ubuntu.com/ubuntu wily-security main   Two or more enabled repositories in one or two lines   cat /etc/apt/sources.list  deb http://archive.ubuntu.com/ubuntu wily main universe   or   deb http://archive.ubuntu.com/ubuntu wily main deb http://archive.ubuntu.com/ubuntu wily universe  sudo apt-add-update enable security  deb http://archive.ubuntu.com/ubuntu wily main universe deb http://archive.ubuntu.com/ubuntu wily-security main universe   or  deb http://archive.ubuntu.com/ubuntu wily main deb http://archive.ubuntu.com/ubuntu wily-security main deb http://archive.ubuntu.com/ubuntu wily universe deb http://archive.ubuntu.com/ubuntu wily-security universe   With deb-src entries   cat /etc/apt/sources.list  deb http://archive.ubuntu.com/ubuntu wily main universe deb-src http://archive.ubuntu.com/ubuntu wily main universe  sudo apt-add-update enable security  deb http://archive.ubuntu.com/ubuntu wily main universe deb-src http://archive.ubuntu.com/ubuntu wily main universe deb http://archive.ubuntu.com/ubuntu wily-security main universe deb-src http://archive.ubuntu.com/ubuntu wily-security main universe   With inactive deb-src entries   cat /etc/apt/sources.list  deb http://archive.ubuntu.com/ubuntu wily main universe # deb-src http://archive.ubuntu.com/ubuntu wily main universe  sudo apt-add-update enable security  deb http://archive.ubuntu.com/ubuntu wily main universe # deb-src http://archive.ubuntu.com/ubuntu wily main universe deb http://archive.ubuntu.com/ubuntu wily-security main universe   The default thing    cat /etc/apt/sources.list  deb http://archive.ubuntu.com/ubuntu wily-security universe  sudo apt-add-update enable default  deb http://archive.ubuntu.com/ubuntu wily universe deb http://archive.ubuntu.com/ubuntu wily-security universe   Only one entry and the disable action   cat /etc/apt/sources.list  deb http://archive.ubuntu.com/ubuntu wily-security universe  sudo apt-add-update disable security  &lt;empty&gt;   Different or the same servers for different or the samerepositories, respect each server   cat /etc/apt/sources.list  deb http://archive.ubuntu.com/ubuntu wily universe deb http://us.archive.ubuntu.com/ubuntu wily main  sudo apt-add-update enable security  deb http://archive.ubuntu.com/ubuntu wily universe deb http://us.archive.ubuntu.com/ubuntu wily main deb http://archive.ubuntu.com/ubuntu wily-security universe deb http://us.archive.ubuntu.com/ubuntu wily-security main   Different Ubuntu releases for different repositories, respect each release   cat /etc/apt/sources.list  deb http://archive.ubuntu.com/ubuntu wily main universe deb http://archive.ubuntu.com/ubuntu trusty main  sudo apt-add-update enable security  deb http://archive.ubuntu.com/ubuntu wily main universe deb http://archive.ubuntu.com/ubuntu trusty main deb http://archive.ubuntu.com/ubuntu wily-security main universe deb http://archive.ubuntu.com/ubuntu trusty-security main   PPAs or other package sources (not-Canonical)  in the sources.list?  Ignore! Don't change the protocols, e.g. https, http, tor, ... For an isolated system, can the entropy decrease or increase? In any sizable system, the number of equilibrium states are much, much greater then the number of non-equilibrium states. Since each accessible micro state is equally probably, it is overwhelmingly likely that we will find the system in an equilibrium state.   However, for a closed system, one that does not interact with any external system, the number of micro states is fixed. Therefore the entropy is fixed.  At any given time, the system will be in one of its micro states. Even if the system is in a micro state that does not look like equilibrium from a macroscopic point of view, its entropy will remain the same, since entropy is a property of all the micro states, not just a given micro state.   So, are the number of accessible micro states (and hence entropy) of an isolated system constant? I have defined my own custom vim file type with highlighting etc.  I would like to open it using the terminal based vim when I double click on it.  I am using mac os x.  Any pointers on how to start on this? Do we have any other evidence other than red shift? Is anyone trying to disapprove inflation? Also, can red shift occur because of large distance, not only because two objects are going farther from each other? Trying to search for multiple file extensions in command line I am trying to find two extensions in command line but when i do it will only return one of the extensions. can you tell me what I am missing?   Here is my command;  [root]# find /etc -name "*.txt" -o -name "*.log" -type f -mtime +7 -exec echo {} \; What causes a "Java Hotspot 64-Bit Server VM Warning"? I get this warning:     Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release   What does it mean? best way to pick a random subset from a collection? I have a set of objects in a Vector from which I'd like to select a random subset (e.g. 100 items coming back; pick 5 randomly). In my first (very hasty) pass I did an extremely simple and perhaps overly clever solution:  Vector itemsVector = getItems();  Collections.shuffle(itemsVector); itemsVector.setSize(5);   While this has the advantage of being nice and simple, I suspect it's not going to scale very well, i.e. Collections.shuffle() must be O(n) at least. My less clever alternative is  Vector itemsVector = getItems();  Random rand = new Random(System.currentTimeMillis()); // would make this static to the class      List subsetList = new ArrayList(5); for (int i = 0; i &lt; 5; i++) {      // be sure to use Vector.remove() or you may get the same item twice      subsetList.add(itemsVector.remove(rand.nextInt(itemsVector.size()))); }   Any suggestions on better ways to draw out a random subset from a Collection? Calculate the display width of a string in C#? A Java version of this question was just answered, and, well, I don't know how to do this in .net.   So how do you calculate the display width of a string in C# / .net? How do I start with in-camera JPEG settings in Lightroom? I'm a novice shooting in RAW and find that half the time my camera JPEG images come out better than my Lightroom tweaks to RAW files.  So to give myself a better start I'd like to apply the JPEG settings that are applied automatically by the camera to my RAW files in lightroom so that initially my RAW files look exactly like the JPEG files.   How can I do this? How do you access the matched groups in a JavaScript regular expression? According to the original paper of , there is no key validation needed when using Curve25519 for Diffie-Hellman Key Exchange. However, where does this property come from? Is there any proof or argumentation available in order to understand this really practical property of Curve25519? Does this mean that each $x$ coordinate could belong to a point $P=(x,y)$ from Curve25519? Is that even possible? I don't know why but now, when i go in material preview or rendered (in solid mode it works fine), my object is entirely gray, or invisible idk, because it has the same color of the background. I've been working for days on this project without having this issue, it suddenly showed up. I tried opening other old projects and suddenly they all do the same so i guess it is some blender program setting that applies for all the projects, but idk how it happened cuz i didn't change anything :/, anyone got any tips? Circuit tester trips new GFCI I replaced a non-protected receptacle with a GFCI type and now my circuit tester trips the GFCI as soon as it is plugged in.  The receptacle tested fine before replacement, ground, neutral, hot, etc.  I've double checked the hot/neutral/ground connections.  I've also tried it with the downstream load disconnected.   The GFCI trips the moment I plug in my circuit tester (before pushing the test button).  Otherwise things check out OK.  I can plug in a power tool without it tripping.  Also, the integrated test/reset button work correctly.   I've read that the integrated test button is the only one that truly matters. Is this correct or should I be concerned? I'm sure a home inspector will red flag this if their tester has the same result.  Update  My tester is by "Commercial Electric".  The tester is one of the palm sized three prong type with three leds to indicate the condition of the circuit and a button on top to test GFCI. It's new from the local box store. A uniformly continuous function maps bounded set to bounded sets I am trying to prove the following:  If $A\subset\mathbb R$ is bounded and $\,f:A\to \mathbb R\,$ is uniformly continuous, then $f[A]$ is bounded.  Could you check my proof?  Let $A \subseteq [-K,K]\subseteq \mathbb R$. Let $\varepsilon = 1$. If $f$ is uniformly continuous there is $\delta$ wuth $|x-y| &lt;\delta$ imply that $|f(x)-f(y)|&lt;1$ for all $x,y\in A$. Let $a \in A$. Then because $A$ is bounded there is a finite number of balls $B(a_n,\delta)$ that cover $A$. Let the number be $N$. Then $f(a)-N \le f(x) \le f(a) + N$ for all $x\in A$. Objective C const NSString * vs NSString * const Some Windows 10 UWP icons not displaying on search, or in settings Motivation behind standard deviation? Let's take the numbers 0-10.  Their mean is 5, and the individual deviations from 5 are -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5 And so the average (magnitude of) deviation from the mean is $30/11 \approx 2.72$.  However, this is not the standard deviation.  The standard deviation is $\sqrt{10} \approx 3.16$.  The first mean-deviation is a simpler and by far more intuitive definition of the "standard-deviation", so I'm sure it's the first definition statisticians worked with.  However, for some reason they decided to adopt the second definition instead.  What is the reasoning behind that decision? QM without complex numbers Recovering *permanently* deleted emails from Gmail person in distress here.  Dont ask me how, but I ended up deleting all my 12,000 inbox emails from Gmail into Trash and then erased my Trash as well. Gmail gave me a warning box and took 20 seconds to delete. This was not what I intended. I have searched high and low to check if there is any way of recovering my 10 years worth of emails and could not find any.  Any one here know of a way, ANY WAY, to recover my accidental permanent deletion of all my 10 years worth of email (deleted from Trash as well)? "no such file or directory" message when deleting a file that exists on NTFS