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  • ZFS: Mirror vs. RAID-Z

    - by John Clayton
    I'm planning on building a file server using OpenSolaris and ZFS that will provide two primary services - be an iSCSI target for XenServer virtual machines & be a general home file server. The hardware I'm looking at includes 2x 4-port SATA controllers, 2x small boot drives (one on each controller), and 4x big drives for storage. This allows one free port per controller for upgrading the array down the road. Where I'm a little confused is how to setup the storage drives. For performance, mirroring appears to be king. I'm having a hard time seeing what the benefit would be of using RAIDZ over mirroring would be. With this setup I can see two options - two mirrored pools in one stripe, or RAIDZ2. Both should protect against 2 drive failures, and/or one controller failure...the only benefit of RAIDZ2 would be that any 2 drives could fail. The storage should be 50% of capacity in both cases, but the first should have much better performance, right? The other thing I'm trying to wrap my mind around is the benefit of mirrored arrays with more than two devices. For data integrity what, if any, would be the benefit of a RAIDZ over a three-way mirror? Since ZFS maintains file integrity what does RAIDZ bring to the table...doesn't ZFS's integrity checks negate the value of RAIDZ's parity?

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  • Raid-5 Performance per spindle scaling

    - by Bill N.
    So I am stuck in a corner, I have a storage project that is limited to 24 spindles, and requires heavy random Write (the corresponding read side is purely sequential). Needs every bit of space on my Drives, ~13TB total in a n-1 raid-5, and has to go fast, over 2GB/s sort of fast. The obvious answer is to use a Stripe/Concat (Raid-0/1), or better yet a raid-10 in place of the raid-5, but that is disallowed for reasons beyond my control. So I am here asking for help in getting a sub optimal configuration to be as good as it can be. The array built on direct attached SAS-2 10K rpm drives, backed by a ARECA 18xx series controller with 4GB of cache. 64k array stripes and an 4K stripe aligned XFS File system, with 24 Allocation groups (to avoid some of the penalty for being raid 5). The heart of my question is this: In the same setup with 6 spindles/AG's I see a near disk limited performance on the write, ~100MB/s per spindle, at 12 spindles I see that drop to ~80MB/s and at 24 ~60MB/s. I would expect that with a distributed parity and matched AG's, the performance should scale with the # of spindles, or be worse at small spindle counts, but this array is doing the opposite. What am I missing ? Should Raid-5 performance scale with # of spindles ? Many thanks for your answers and any ideas, input, or guidance. --Bill Edit: Improving RAID performance The other relevant thread I was able to find, discusses some of the same issues in the answers, though it still leaves me with out an answer on the performance scaling.

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  • Defeating the RAID5 write hole with ZFS (but not RAID-Z) [closed]

    - by Michael Shick
    I'm setting up a long-term storage system for keeping personal backups and archives. I plan to have RAID5 starting with a relatively small array and adding devices over time to expand storage. I may also want to convert to RAID6 down the road when the array gets large. Linux md is a perfect fit for this use case since it allows both of the changes I want on a live array and performance isn't at all important. Low cost is also great. Now, I also want to defend against file corruption, so it looked like a RAID-Z1 would be a good fit, but evidently I would only be able to add additional RAID5 (RAID-Z1) sets at a time rather than individual drives. I want to be able to add drives one at a time, and I don't want to have to give up another device for parity with every expansion. So at this point, it looks like I'll be using a plain ZFS filesystem on top of an md RAID5 array. That brings me to my primary question: Will ZFS be able to correct or at least detect corruption resulting from the RAID5 write hole? Additionally, any other caveats or advice for such a set up is welcome. I'll probably be using Debian, but I'll definitely be using Linux since I'm familiar with it, so that means only as new a version of ZFS as is available for Linux (via ZFS-FUSE or so).

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  • Software mirroring (RAID1) versus "Fake Raid" for new Windows 7 install

    - by kquinn
    I've just ordered two new hard drives for my main desktop and a copy of Windows 7 Professional 64-bit. I'd like to do a clean install of Win7 onto the new drives (leaving my old XP Pro boot partition around for a while in case something goes disastrously wrong, etc.). I want to have them set up in mirrored (RAID-1) mode. My understanding is that Win7 Pro can do software mirroring, but can I set this up directly at install time? If so, how? Note that I'd like the disk to be split into three partitions (OS/Apps&Data/Bulk data), all of which should be mirrored. Would it be better (more reliable or faster) to use my motherboard's hardware RAID support? My motherboard is an older nVidia nForce 680i SLI, which is not the most stable of motherboards, and I'm not sure how trustworthy its RAID1 configuration might be (or if Win7 could even detect and install onto a hardware-mirrored volume). Also, the performance characteristics of RAID1 are rather different than RAID0 or RAID5, and I'm wondering if Win7's software mirroring might actually be faster than hardware RAID1 (for example, I'm more of a Unix admin when I have to wear the sysadmin hat, and I've had great success deploying ZFS; most hardware RAID1 implementations have to read both disks and compare results to look for data errors, but ZFS can read from only one disk in the mirror and just use the built-in checksum, meaning it can have up to 2x the number of reads in-flight, as long as there's no data corruption). Edit: Okay, my question about whether Windows 7 can do software mirroring has been answered, and it can. I'm still unsure whether Windows software RAID or my motherboard's hardware "fake RAID" function is a better choice, though. Remember, I'm only interested in mirroring -- not the more complicated striping or parity operations that generally show the poor performance of crappy motherboard RAID solutions.

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  • Truncated content with Apache on Vagrant VM

    - by Nev Stokes
    I'm using Vagrant to run a CentOS VM in order to try and achieve local development parity with our live servers. I've symlinked /var/www/html with the /vagrant shared directory and am forwarding port 80 for viewing at http://localhost:4567. I'm developing using SublimeText 2 on OS X Mountain Lion. Once I figured that iptables was tripping me up, all was well and good. Until I noticed something strange. I have a sample HTML page consisting of several paragraphs of lorem copy. I can view this fine in a browser on OS X. But when I make an edit, for example removing a paragraph, and refresh the content is truncated with the paragraph I deleted still visible. When I cat the files on the server I can see the changes I made but these aren't even reflected when I curl localhost. I strongly suspect that it's a problem with my Apache settings — with which I didn't really tinker — as the issue doesn't arise when I stop Apache and run sudo python -m SimpleHTTPServer 80 in the directory to view pages instead. What gives?

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  • What is the best private cloud storage setup

    - by vdrmrt
    I need to create a private cloud and I'm searching for the best setup. These are my 2 most important requirements 1. Disk and system redundant 2. Price / GB as low as possible The system is going to be used as backup setup which will receive data 24/7 over SFTP and rsync. High throughput is not that important. I'm planning to use glusterfs and consumer grade 4TB hard-drives. I have worked out 3 possible setups 3 servers with 11 4TB HDD Setup up a replica 3 glusterfs and setup each hard drive as a separate ext4 brick. Total capacity: 44TB HDD / TB ratio of 0.75 (33HDD / 44TB) 2 servers with 11 4TB HDD The 11 hard-drives are combined in a RAIDZ3 ZFS storage pool. With a replica 2 gluster setup. Total capacity: 32TB (+ zfs compression) HDD / TB ratio of 0.68 (22HDD / 32TB) 3 servers with 11 4TB consumer hard-drives Setup up a replica 3 glusterfs and setup each hard-drive as a separate zfs storage pool and export each pool as a brick. Total capacity: 32TB (+ zfs compression) HDD / TB ratio of 0.68 (22HDD / 32TB) (Cheapest) My remarks and concerns: If a hard drive fails which setup will recover the quickest? In my opinion setup 1 and 3 because there only the contents of 1 hard-drive needs to be copied over the network. Instead of setup 2 were the hard-drive needs te be reconstructed by reading the parity of all the other harddrives in the system. Will a zfs pool on 1 harddrive give me extra protection against for example bit rot? With setup 1 and 3 I can loose 2 systems and still be up and running with setup 2 I can only loose 1 system. When I use ZFS I can enable compression which will give me some extra storage.

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  • How to install (old) packages for Ubuntu 9.04?

    - by wchrisjohnson
    Based on some excellent feedback by Mark here (http://serverfault.com/questions/285598/should-i-clone-a-physical-server-to-create-a-vm-for-a-staging-server), today I was able to use the vmware converter to clone my production server for a staging server. However the nic won't come up no matter what I do. I attempted to inistall vmware tools, as I suspect that the fact that it is not installed might prevent the nic from working. (I have the nic set as a vmxnet3 card in the vm settings). The install failed because there were several dependencies missing as well as the Linux headers. Given that Ubuntu 9.04 has been EOL'd, the packages I need to install to get the vmware tools to install are no longer available. I doubt the ubuntu 9.04 install CD has the packages on it. What are my options? I'd rather not upgrade the version of Ubuntu yet, as the point of the vm right now is to maintain parity with the production server. Might I have better luck resetting the driver to use vmxnet2 instead of the vmxnet3? Thanks in advance! Chris

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  • How do I connect to and factory reset a Catalyst 3560 Switch?

    - by Josh
    My company just bought another company. In their server room they had some older hardware, which I would like to repurpose. One of these is a Cisco Switch: C3560G-48TS-S. I found some instructions about this switch here but this is not a guide for a beginner. I have no idea how to connect to this thing to begin running the commands. It says Configure the PC terminal emulation software for 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control. But I can't find anything on how to do this (assuming with telnet?) or even what program to use. I also don't know how to find the IP address of the device to connect to it. My research also says once I get in there, I need to run clear config all Is this the right command? Also, what if I can't get the username and password for these devices? Is there some way to factory reset (my only experience is with devices that have a hardware reset button) EDIT: I should note that when I push the button on the front the three lights blink, which according to the documentation indicated the switch is configured and "not available for express setup"

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  • Programmatically Insert Page Break in Active Report

    - by Kevin Babcock
    I've been scouring the web for a good example, but cannot figure out how to add a page break to an Active Reports report programmatically. The reports I'm working with usually require 1-2 pages for each record. In order to support dual-sided printing of the reports I want to insert a blank page for each record that uses an odd number of pages, ensuring that each new record is printed on the front of each printed page. I'm very new to Active Reports, so any suggestions, code samples, or links are much appreciated!

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  • Python Wildcard Import Vs Named Import

    - by Dan
    Ok, I have some rather odd behavior in one of my Projects and I'm hoping someone can tell me why. My file structure looks like this: MainApp.py res/ __init__.py elements/ __init__.py MainFrame.py Inside of MainFrame.py I've defined a class named RPMWindow which extends wx.Frame. In MainApp.py this works: from res.elements.MainFrame import * And this does not: from res.elements.MainFrame import RPMWindow I realize that the wild card import won't hurt anything, but I'm more interested in understanding why the named import is failing when the wild card succeeds.

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  • Resizing QT's QTextEdit to Match Text Height: maximumViewportSize()

    - by Aaron
    I am trying to use a QTextEdit widget inside of a form containing several QT widgets. The form itself sits inside a QScrollArea that is the central widget for a window. My intent is that any necessary scrolling will take place in the main QScrollArea (rather than inside any widgets), and any widgets inside will automatically resize their height to hold their contents. I have tried to implement the automatic resizing of height with a QTextEdit, but have run into an odd issue. I created a sub-class of QTextEdit and reimplemented sizeHint() like this: QSize OperationEditor::sizeHint() const { QSize sizehint = QTextBrowser::sizeHint(); sizehint.setHeight(this->fitted_height); return sizehint; } this-fitted_height is kept up-to-date via this slot that is wired to the QTextEdit's "contentsChanged()" signal: void OperationEditor::fitHeightToDocument() { this->document()->setTextWidth(this->viewport()->width()); QSize document_size(this->document()->size().toSize()); this->fitted_height = document_size.height(); this->updateGeometry(); } The size policy of the QTextEdit sub-class is: this->setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::Preferred); I took this approach after reading this post. Here is my problem: As the QTextEdit gradually resizes to fill the window, it stops getting larger and starts scrolling within the QTextEdit, no matter what height is returned from sizeHint(). If I initially have sizeHint() return some large constant number, then the QTextEdit is very big and is contained nicely within the outer QScrollArea, as one would expect. However, if sizeHint gradually adjusts the size of the QTextEdit rather than just making it really big to start, then it tops out when it fills the current window and starts scrolling instead of growing. I have traced this problem to be that, no matter what my sizeHint() returns, it will never resize the QTextEdit larger than the value returned from maximumViewportSize(), which is inherited from QAbstractScrollArea. Note that this is not the same number as viewport()-maximumSize(). I am unable to figure out how to set that value. Looking at QT's source code, maximumViewportSize() is returning "the size of the viewport as if the scroll bars had no valid scrolling range." This value is basically computed as the current size of the widget minus (2 * frameWidth + margins) plus any scrollbar widths/heights. This does not make a lot of sense to me, and it's not clear to me why that number would be used anywhere in a way that supercede's the sub-class's sizeHint() implementation. Also, it does seem odd that the single "frameWidth" integer is used in computing both the width and the height. Can anyone please shed some light on this? I suspect that my poor understanding of QT's layout engine is to blame here.

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  • Watin - Watin.Core.Exceptions.ElementNotFoundException

    - by potterosa
    I have code that runs that gives me the error : Could not find a 'INPUT (text password textarea hidden) or TEXTAREA' tag containing attribute name with value ________ (It's testing a website) It says it can't find a What reason could it be that it can't find it? It finds others without an issue on other pages, but this page for some odd reason it baulks? How can that be?

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  • Flex 4 - What makes a GC root?

    - by Michael Brewer-Davis
    What are the rules for something to be a GC root in Flash? I'm using the Flash Builder 4 profiler, and I'm finding odd things are labeled as GC roots in the object reference details (e.g., an Image control that is no longer in the display list, nor static).

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  • Which platform can we expect one's complement being used there?

    - by Jian Lin
    For some questions such as checking whether a number is odd or even, I noted the comment, a & 1 won't work when it is a one's complement machine or when the code is ported to a platform that uses one's complement. Since 30 years ago on the Superboard, TRS-80, Apple II, I haven't seen a system with one's complement. Are there popular systems that use one's complement still, or do we have some cell phone or mobile device that uses one's complement?

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  • What does Silverlight 4 Tools only give partial intellisense?

    - by Edward Tanguay
    I finally got Silverlight 4 Toolkit installed , referenced and working after the difficulty of finding the right namespace described in this question. But intellisense doesn't work fully: after I type "tk:", it doesn't pop up the various controls I have available, but if I type a control name out, e.g. DockPanel, then it works, as shown below. It will even give me intellisense after I type tk:DropPanel, which is odd. How can I get intellisense to work in all cases for the Silverlight 4 Toolkit?

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  • Flex 3.5 Accordion and TabNavigator Index Change Bug

    - by majgis
    I'm using Flex 3.5 with Adobe Flex Builder 3. I have found that if you very rapidly click between multiple headers of an accordion component or the tabs of TabNavigator, these components will begin to exhibit odd, unexpected behavior. Has anyone else experienced this behavior and do you know of a patch that can prevent the user from getting in a situation where the tab/header they click on is not the one made visible?

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  • Are there people using scheme out there?

    - by Nick
    Hey, I have just started to study computer sciences at the university where they teach us programming in scheme. Since i have learned c++ for the last 6 years, scheme appears a little odd to me. But they tell me you can write any program you can write in C or Java with it. Is anybody really using this language?

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  • h:dataTable alternating rows in JSF2

    - by Benchik
    Hello. I'm trying to make alternating rows in JSF2 h:dataTable (no richfaces or such) but i get an unexpected result. the table is built but it has a white grid shown (but i didn't specifiy any border) and there's no buttom line under each row. The CSS: .order-table{ border-collapse:collapse; } .order-table-header{ text-align:center; background:none repeat scroll 0 0 #E5E5E5; border-bottom:1px solid #95bce2; padding:16px; } .order-table-odd-row{ text-align:center; background:none repeat scroll 0 0 #FFFFFFF; border-top:1px solid #000000; } .order-table-even-row{ text-align:center; background:none repeat scroll 0 0 #ecf6fc; border-top:1px solid #BBBBBB; } table.order-table tr.over { background-color: #bcd4ec; } The table: <h:dataTable id="personsTable" value="#{personController.allPersons}" var="bean" styleClass="order-table" headerClass="order-table-header" rowClasses="order-table-odd-row,order-table-even-row"> <h:column> <f:facet name="header"> <h:outputText value="First Name" /> </f:facet> <h:outputText value="#{bean.firstName}"/> </h:column> <h:column> <f:facet name="header"> <h:outputText value="Last Name" /> </f:facet> <h:outputText value="#{bean.lastName}"/> </h:column> <h:column> <f:facet name="header"> <h:outputText value="Phone" /> </f:facet> <h:outputText value="#{bean.phone}"/> </h:column> </h:dataTable> and a small JQuery script: <script type="text/javascript"> $(document).ready(function(){ $(".order-table tr").mouseover(function(){ $(this).addClass("over"); }); $(".order-table tr").mouseout(function(){ $(this).removeClass("over"); }); }); </script> The result is (notice the white grid that came from i don't know where. And also no underline which should come from the CSS): http://imagebin.org/132574

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  • PHP object access using string

    - by Rob Waring
    Hi all, I have an object in PHP with some very odd property names. I just need to know how to access a property when it's name is "//www.w3.org/1999/02/22-rdf-syntax-ns#type". I found something that suggested $object->{'//www.w3.org/1999/02/22-rdf-syntax-ns#type'}; but that doesn't seem to work. Thanks in advance Rob

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  • Regex to parse youtube yid

    - by novaurora
    Example URLs http://www.youtube.com/user/Scobleizer#p/u/1/1p3vcRhsYGo http://www.youtube.com/watch?v=cKZDdG9FTKY&feature=channel http://www.youtube.com/watch?v=yZ-K7nCVnBI&playnext_from=TL&videos=osPknwzXEas&feature=sub Any regex that will pull the correct YID from all 3 of these use cases? The first case is especially odd. Thank you.

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  • where to set wait cursor in long operation in MVP pattern?

    - by Benny
    For a long operation that will be executed in presenter, where to set the wait cursor? in View? the view shouldn't know too much about business logic, it is passive. in presenter? seems odd in presenter to call UI code. add method to View interface, like SetWait(bool), and call it in presenter? So what do you think?

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  • Time complexity of a recursive algorithm

    - by Passonate Learner
    How can I calculate the time complexity of a recursive algorithm? pow1(x,n) if(n==0){ return 1 } else{ return x * pow1(x, n-1) } pow2(x,n) if(n==0){ return 1 } else if(n is odd integer){ p = pow2(x, (n-1)/2) return x * p * p } else if(n is even integer){ p = pow2(x, n/2) return p * p }

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