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• Configure Iptables to allow a PHP-app accessing a port-nr

  - by Camran

  I have a php-application which connects to another app called Solr (database search engine). I can via this php app add/remove documents (records) from the Solr index. However, the Solr security is low, and anybody with the right port nr can access Solr and remove documents (records). I wonder, is it possible to ONLY allow my own php-app to have access to Solr somehow? Prefferably via Iptables. I am thinking I can only allow my own servers IP to that port, and it would solve my problem, because PHP is a server-side code. But I am not sure. About the Php-app: The website is a classifieds website, and when users wants to add or remove classifieds, they do so through a php app, which is this one. The app has a function which connects to solr and updates the database (index). I appreciate detailed answers... Thanks

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• What do I need to write a small game on Linux?

  - by Michas

  I want to make a simple game: 2d, single-player, without tons of animations and special effects. I am not interested in ready to use game engines, I want to learn to write some code in a quite universal language. I am using Linux (AMD64) and looking for something easy with nice library for games. I do not want to mix few languages, most of them are in fact fast enough themselves for my needs. Cross platform would be an advantage, however all I need is a good Linux support. I have been considering few solutions. Ruby + Language looks very nice. + I am going to learn Ruby. - I am afraid I can have problems with additional libraries. - This thread about game libraries for Ruby could be longer. SDL + C + It is used for games. + It is very easy to set up. + There is a lot of additional libraries. + It is cross-platform. - The solution is quite low level. - The language is sometimes quite hard to read. QT + C++ + It is very easy to set up. + The standard QT libraries supports everything I can possibly need. + It is cross-platform. + The documentation is good. - The compilation is slow. - The language looks horrible. - The size of standard QT libraries is too big to comprehend. Environment of web browser + I am going to learn something more about this environment. + It is somewhat used for games. + It is quite cross-platform. - It would be too much experimental. Java + It is used for games. + The standard Java libraries supports everything I can possibly need. + It is cross-platform. - It is quite hard to set up. - The size of standard Java libraries is too big to comprehend. - The source code in Java could look better. - I think I do not want to learn Java. Google Go + I am going to learn Google Go. - There is big problem with libraries. - The solution would be quite low level. Python + It looks some people do games in Python, according to this thread. + It looks there are probably more libraries than for Ruby. - The Ruby language looks better. - I think I do not want to learn Python. C++ + something else + It is used for games. + It would be probably cross-platform. + There is a lot of libraries. - I do not need C++ extensions over C. - Compilation could be slow, there are fast compilers for C, not for C++. Haskell + I am going to learn Haskell. - Many things about programming computer games looks too much imperative. - It looks I can have some problems with libraries. - Compilation (GHC) looks slow. There is probably something more to consider. Does anyone have experience in making small games for Linux in non mainstream solutions? Does anyone have an advice for me?

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• Best suited multi-function printer for Linux usage from a few choices

  - by Nakedible

  I want a cheap multi-function printer for Linux usage. I'm looking for rock solid scanning and printing that works with big images. I'd prefer drivers that are available in Debian, or other drivers that are open source, but will settle for proprietary drivers if they are well contained and clean. Some choices I have are: Samsung SCX-4300 HP LaserJet M1120 MFP Samsung SCX-4500 Canon i-SENSYS MF4010 Brother DCP-7040 I am also interested in opinions what printer communication language is best for Linux usage for cheap printers. PostScript is nice, of course, but low-end PostScript printers often have problems when printing complex (large) PostScript files. It seems Samsung printers use SPL for communication, HP uses XQX and ZJS, then there's ofcourse PCL.

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• RAID administration in Debian Lenny

  - by Siim K

  I've got an old box that I don't want to scrap yet because it's got a nice working 5-disk RAID assembly. I want to create 2 arrays: RAID 1 with 2 disks and RAID 5 with the other 3 disks. The RAID card is Intel SRCU31L. I can create the RAID 1 volume in the console that you access with Ctrl+C at startup. But it only allows for creation of one volume so I can't do anything with the 3 remaining disks. I installed Debian Lenny on the RAID 1 volume and it worked out nicely. What utilites could I now use to create/manage the RAID volumes in Debian Linux? I installed the raidutils package but get an error when trying to fetch a list: #raidutil -L controller or #raidutil -L physical # raidutil -L controller osdOpenEngine : 11/08/110-18:16:08 Fatal error, no active controller device files found. Engine connect failed: Open What could I try to get this thing working? Can you suggest any other tools? Command #lspci -vv gives me this about the controller: 00:06.1 I2O: Intel Corporation Integrated RAID (rev 02) (prog-if 01) Subsystem: Intel Corporation Device 0001 Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr- Step ping- SERR+ FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort - <MAbort- >SERR- <PERR- INTx- Latency: 64, Cache Line Size: 32 bytes Interrupt: pin A routed to IRQ 26 Region 0: Memory at f9800000 (32-bit, prefetchable) [size=8M] [virtual] Expansion ROM at 30020000 [disabled] [size=64K] Capabilities: <access denied> Kernel driver in use: PCI_I2O Kernel modules: i2o_core

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• Run Windows batch file on schedule as non-Administrator user

  - by Evgeny

  I'm running Windows XP x64 SP2. I have a Windows batch file that with some Robocopy commands that I want to run on schedule. I created a scheduled task for it, running as a dedicated user (not the user I'm logged on as), but it simply did not run. I could see successful logon events in the security log, so it got that far, but the commands in the batch file definitely weren't getting executed. After reading through all of http://social.technet.microsoft.com/Forums/en-US/winservermanager/thread/d47d116e-10b9-44f0-9a30-7406c86c2fbe/ I tried making the target user account an Administrator and that fixed it - the batch file ran just fine. Nothing else seemed to work. The thing is, I want it to run under a low-privileged account. Does anyone know how can I get a batch file to run on schedule as a non-Administrator?

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• Is there a way to create a consistent snapshot/SnapMirror across multiple volumes?

  - by Tomer Gabel

  We use a NetApp FAS 6-series filer with an application that spans multiple volumes. For backup purposes I would like to create a consistent snapshot that spans these volumes at the same point in time (or at least with an extremely low delta); additionally, we'd like to to use SnapMirror to replace the production environment to test volumes. The problem is in creating a consistent snapshot/SnapMirror, since these commands are not transactional and do not take multiple parameters. I tried scripting consecutive "snap create" or "snapmirror resync" commands via SSH, but there's always a 0.5-2 second difference between each snapshot. It's currently "good enough", but I'm seriously concerned about the consistency impact with increased load (we're currently in pre-production). Has anyone managed to create a consistent snapshot that spans several volumes? How did you pull it off?

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• MacPro 1,1 video's card

  - by alexus

  I just bought a Mac Pro 1,1 from my coworkers and I'm looking to upgrade video card as the one inside is very noisy. What are my options? Basically I'm not looking to spend a lot of money, in fact i'd rather to spend as little as possible and get low end or mid range card, I'm not really playing games all that much so pretty much anything will do, I'd prefer 2xx series though. Current Mac Pro sells w/ GT120, Apple sells upgrade kit for $149 (which is okay, I just not sure if I'll be able to use this card on such an old Mac Pro)

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• CCD vs. CMOS webcams

  - by rob

  Several years ago, I tried a CMOS-based webcam and it really sucked. It needed an extremely brightly-lit room to work. Around the same time, I also tried a CCD camera and it worked great. But since then, I've heard that CMOS technology has advanced considerably. Is it still the case that CCD webcams will give you a better picture, or can CMOS webcams also produce a picture of similar quality at moderate to low light levels? What type of camera is used in modern integrated webcams and cameras? If CMOS cameras actually are competitive these days, how do you tell if a webcam has a newer-generation CMOS sensor instead of one of the older sensors?

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• can't connect to vsftpd from outside network

  - by rick

  i know this has been asked many times before, but nothing seems to resolve my issue. i have vsftpd running on ubuntu 10.04. i can connect with ftp localhost on the machine. i can connect from another machine in my network. i just cannot connect from outside. the machine is behind an airport extreme managed by airport utility on a mac. 21 is open as per nmap: macmini:~$ nmap localhost Starting Nmap 5.21 ( http://nmap.org ) at 2011-04-10 23:49 EDT Nmap scan report for localhost (127.0.0.1) Host is up (0.00045s latency). Hostname localhost resolves to 2 IPs. Only scanned 127.0.0.1 rDNS record for 127.0.0.1: localhost.localdomain Not shown: 997 closed ports PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 631/tcp open ipp netstat says 21 is listening: macmini:~$ netstat -lep --tcp | grep ftp (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) tcp 0 0 *:ftp *:* LISTEN iptables: macmini:~$ sudo iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination when i try to connect from my external IP (or a dyndns name which resolves there) it times out. ("control connection timed out") as i know very little about networking, i feel like something may jump out as clearly wrong?

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• Optimizing Disk I/O & RAID on Windows SQL Server 2005

  - by David

  I've been monitoring our SQL server for a while, and have noticed that I/O hits 100% every so often using Task Manager and Perfmon. I have normally been able to correlate this spike with SUSPENDED processes in SQL Server Management when I execute "exec sp_who2". The RAID controller is controlled by LSI MegaRAID Storage Manager. We have the following setup: System Drive (Windows) on RAID 1 with two 280GB drives SQL is on a RAID 10 (2 mirroed drives of 280GB in two different spans) This is a database that is hammered during the day, but is pretty inactive at night. The DB size is currently about 13GB, and is used by approximately 200 (and growing) users a day. I have a couple of ideas I'm toying around with: Checking for Indexes & reindexing some tables Adding an additional RAID 1 (with 2 new, smaller, HDs) and moving the SQL's Log Data File (LDF) onto the new RAID. For #2, my question is this: Would we really be increasing disk performance (IO) by moving data off of the RAID 10 onto a RAID 1? RAID 10 obviously has better performance than RAID 1. Furthermore, SQL must write to the transaction logs before writing to the database. But on the flip side, we'll be reducing both the size of the disks as well as the amount of data written to the RAID 10, which is where all of the "meat" is - thereby increasing that RAID's performance for read requests. Is there any way to find out what our current limiting factor is? (The drives vs. the RAID Controller)? If the limiting factor is the drives, then maybe adding the additional RAID 1 makes sense. But if the limiting factor is the Controller itself, then I think we're approaching this thing wrong. Finally, are we just wasting our time? Should we instead be focusing our efforts towards #1 (reindexing tables, reducing network latency where possible, etc...)?

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• Software for formatting / web-publishing tutorial-type, technical articles

  - by gojira

  I want to put some of my own technical writing on the web: tutorials, how-to's, conceptual articles about programming etc. I write mostly for myself yet, but think others can benefit from it so I want to put it online, and I also have plans of making everything more coherent and turning it into a book. My articles are not meant as a blog, they're just meant as a collection of tutorials and how-to's, but I think a blog-type software would probably be the most appropriate mode of formatting that kind of stuff. Right now I am using the blog feature of cite u like, which is very low tech and I really need something better. On my wish list is, among other things: code snippets in scrollable boxes syntax highlighting for source code snippets tagging articles with graphical icons according to topic, like in slashdot of course users (i.e. readers) should be able to comment on articles Also, just more options than a super-simple blog should look slick! should not look wikipedia-like Is there any software you can recommend for this purpose?

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• Download acceleration with jigdo?

  - by james

  Im using jigdo-lite to download a Debian DVD ISO. I already have the CD version of the image, so I added the CD files to the task. Now I need to download many files (not all) of the DVD ISO. The default jigdo-lite uses wget to download files. It seems jigdo (wget) downloads only one file at a time with one connection. So I'm getting a low download speed. How can I accelerate the download speed using jigdo? Possible Solutions: Using different download manager with jigdo. Is it possible? If yes, How? Using jigdo (wget) to download multiple files at once. How? Getting download links of remaining files to download so that they can be downloaded with a download manager and later added to jigdo iso. How?

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• Xinetd , vncserver memory requirement

  - by JP19

  Hi, I am installing the following on a low memory system: vnc4server xinetd xterm openbox obconf I will only occasionally be logging into the vncs for some admin work. My question is: 1) Does xinetd take memory / cpu even when vncserver is not running? If so, can I "run" xinetd on demand (how)? And if no, any idea how much memory it will take when vncserver is not running? 2) Does vncserver take substantial memory when no clients are connected? 3) Do openbox/obconf take memory when vncserver is running but no client are connected? 4) Do openbox/obconf take memory when no vncserver is running? thanks JP

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• AMD Phenom II X4 965 crossfire motherboard

  - by Nick

  I am trying to build a cheap mining rig. I wanted to use the AMD Phenom II X4 965 (HDZ965FBGMBOX) processor as it got very good reviews and benchmarks, and is inexpensive. However, I am having trouble finding motherboards with crossfire support for 2 GPUs. AMD's website only lists five compatible motherboards, of which only one has crossfire support. Worse, it is expensive and seems to be obsolete and no longer available. I have trouble believing that there are only five compatible motherboards for that CPU. Are there any low-end motherboards that are both compatible with the AMD Phenom II X4 965 and have CrossFire support? (Is there a way to find this sort of information, like a central site that lists motherboards and their technical specifications?)

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• Web application and remote storage of files

  - by Matt

  Hi have a web application that can store lots and lots of files on the server. i.e. users upload data to it. The files are stored below a particular storage path. The web host will be an IBM xseries 345. However, the disks are really expensive so we would like to put the files onto a less expensive server. Now here is the question. Should I use an NFS mount on the IBM server of a path on the storage server? Or should I write some scripts to upload the files to the storage server instead. Both the storage server and the web host are on the same network. Only the web server is visible to the world. Is NFS performance suitable for an expected low to moderately loaded server?

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• NVRAM for journals on Linux?

  - by symcbean

  I've been thinking about ways of speeding up disk I/O, and one of the bottlenecks I keep coming back to is the journal. There's an obvious benefit to using an SSD for the journal - over and above just write caching unless of course I just disable the journal with the write cache (after all devicemapper doesn't seem to support barriers). In order to get the benefits from using a BB write cache on the controller, then I'd need to disable journalling - but then the OS should try to fsck the system after an outage. Of course if the OS knows what's in the batter-backed memory then it could use it as the journal - but that means it must be exposed as a block device and only be under the control of the operating system. However I've not been able to find a suitable low-cost device (no, write-levelling for Flash is not adequate for a journal, at least one which uses Smartmedia). While there's no end of flash devices, disk/array controllers with BB write caches, so far I've not found anything which just gives me non-volatile memory addressable as a block storage device.

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• Tools to automate recording streaming radio

  - by Stan

  Is there any tool that can automate recording online streaming radio? I've been use totalrecorder which it has below upside: 1. Handy scheduler. 2. Support create recording templates, so I can customize some high/low quality recording. The downside are it requires to open the streaming radio in browser and can't have another sound source. It's recording what comes out from the speaker. What I am looking for is given a online radio url, and the tool can record the audio stream. No matter if I am playing any other music or not. Thanks.

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• Which is generally considered faster or best practice: symlinks or Apache aliases?

  - by Christopher W. Allen-Poole

  I'm curious as to what most people's views are on this subject. Personally, I will almost always prefer symlinks unless I have no other option -- I find that it is far more obvious when someone is navigating the file system, but, on the other hand aliasing is more platform independent. Windows XP, for example, doesn't have anything remotely comparable to symlinks (NTFS junctions are not interpreted correctly by at least some environments), which means that anything which relies on symlinks in a *nix based system cannot be transferred. (I know that Windows 64x OS's have symlinks, but I've not seen if they can be read correctly by the environments previously mentioned) In addition to this, I was also wondering which is considered faster. Is this even possible to know? Do you have a conjecture? I would imagine that since symlinks are generally more low-level than Apache it would make sense that they would be referenced faster, but, on the other hand, I would guess that Apache is required to do a lookup in either case so it would be disk read dependent.

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• reduce memory footprint of java virtual machine

  - by Lorenzo Boccaccia

  I've a citrix server where multiple users use a multiple java application. Is there a way to reduce the memory footprint of the jvm itself? The max heap is already set fairly low (64MB), as the permgen (32MB) space and we're to the point that the jvm itself uses way more memory than the application itself (the committed area is around 350MB) I'm looking for a way to reduce the jvm ram usage or to make the all the applications run within the same jvm or any other way of sharing common pages between running jvm (if possible) or try switch to switch to a jvm if a jvm exists having optimizations relative to this scenario currently using windows 2003 server and sun java virtual machine 1.6

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• Transferring websites from x64 to x86 server

  - by Ke

  Hi, I run a x64 staging server here along with the following: Solr Java etc. However, I am about to get a linode vps for production and quickly realising that x86 is the way to go for their lowest RAM package (thinking to upgrade later). My staging server is x64 with 12gb ram, so going down to 300mb ram is going to feel devilishly slow ;/ Here are my questions: 1) Will I have problems transferring my scripts, dbs etc from a x64 to x86 server? e.g. solr indexes 2) Is it worth going for the x86 package? I am probably going to upgrade later down the line and x64 might be better for the servers with more RAM? should I stick with x64 instead as there isnt much difference when using with low RAM? Cheers Ke

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• Free DNS software with failover support?

  - by Lin

  I'm looking for DNS software that can accomplish the following: Check health of all A records at set intervals If server is unresponsive after multiple successive checks, replace A record with a working server When a server is down, check it periodically. Once it's up, restore normal A records Here's an equivalent I thought of: Run DNS servers with very low TTL (minutes) Use a cron job to periodically query all webservers Use sed to replace A records if need be, and then restart DNS server I have a hard time believing there isn't already something that can accomplish the above. I'm not looking for a paid service, and I'm restricted to anything I can run with root access to a VPS. Any suggestions would be great. Thanks!

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• Linux - real-world hardware RAID controller tuning (scsi and cciss)

  - by ewwhite

  Most of the Linux systems I manage feature hardware RAID controllers (mostly HP Smart Array). They're all running RHEL or CentOS. I'm looking for real-world tunables to help optimize performance for setups that incorporate hardware RAID controllers with SAS disks (Smart Array, Perc, LSI, etc.) and battery-backed or flash-backed cache. Assume RAID 1+0 and multiple spindles (4+ disks). I spend a considerable amount of time tuning Linux network settings for low-latency and financial trading applications. But many of those options are well-documented (changing send/receive buffers, modifying TCP window settings, etc.). What are engineers doing on the storage side? Historically, I've made changes to the I/O scheduling elevator, recently opting for the deadline and noop schedulers to improve performance within my applications. As RHEL versions have progressed, I've also noticed that the compiled-in defaults for SCSI and CCISS block devices have changed as well. This has had an impact on the recommended storage subsystem settings over time. However, it's been awhile since I've seen any clear recommendations. And I know that the OS defaults aren't optimal. For example, it seems that the default read-ahead buffer of 128kb is extremely small for a deployment on server-class hardware. The following articles explore the performance impact of changing read-ahead cache and nr_requests values on the block queues. http://zackreed.me/articles/54-hp-smart-array-p410-controller-tuning http://www.overclock.net/t/515068/tuning-a-hp-smart-array-p400-with-linux-why-tuning-really-matters http://yoshinorimatsunobu.blogspot.com/2009/04/linux-io-scheduler-queue-size-and.html For example, these are suggested changes for an HP Smart Array RAID controller: echo "noop" > /sys/block/cciss\!c0d0/queue/scheduler blockdev --setra 65536 /dev/cciss/c0d0 echo 512 > /sys/block/cciss\!c0d0/queue/nr_requests echo 2048 > /sys/block/cciss\!c0d0/queue/read_ahead_kb What else can be reliably tuned to improve storage performance? I'm specifically looking for sysctl and sysfs options in production scenarios.

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• RDP or SSH connection trough Windows 2008 server VPN hang after a while

  - by xt4fs

  I have been experiencing a very strange issue with our VPN setup on Windows Server 2008. That server is running as a Xen Virtual Machine. We use it for two purposes, permit our mobile workers to connect to another server hosted somewhere else that only allow that ip, and use it to RDP or ssh to many other virtual machine on the same server. The server has no performance issue and still a load of memory free. All other virtual machine has no problem whatsoever. Many of those virtual machine have public IP (web servers) and all their firewall are set to allow only ssh connection or RDP connection from their local interface. When I am connecting directly with either ssh or RDP to one of the other virtual machine everything run without any issues. However, when I am doing so through the VPN after some time the connection just hang, it usually continue after some time (5 or 10 minutes). It seems as more there is network usage more often it happen to a point where it is completely unusable. The worst thing I can do to hang it faster is to actually ping the vpn client IP from the local network, after some time the latency increase until it hang. This happen even if I do RDP to the local ip of the VPN server trough the VPN. The server report no problem and if I disconnect to the vpn and reconnect right away everything is alright. There is nothing wrong in the VPN server log. I have taught at the beginning that it could have been an issue with the Host server so I try to RDP,ssh directly to the guest and I have experience no issue while doing this, so it really seems to be a problem with the VPN server on Windows server 2008. Another very weird thing is it does not seems to be of any issue if you only do Internet (NAT) without trying to connect to any local ips.

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• Removing RAID on a DELL power-edge server

  - by Simon Callan

  We have a Dell Power-edge T110 server, with either a PERC S100 or S300 raid controller (I suspect S100), and 2 x 500GB SATA hard discs. These discs are running in RAID-1 configuration, (either 1 or 2 virtual discs), and on top of this, we have the C and D drives. As we are running low on disc space, we are looking at dropping the RAID to get some disc space back. Is it possible to split the discs back into 2 seperate hards discs that the OS can see, without losing all the data on the drives? Even better, would it be possible to split the D: drive, leaving the OS C: drive in RAID1 configuration?

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• What lasts longer: Data stored on non-volatile flash RAM, optical media, or magnetic disk?

  - by Chris W. Rea

  What lasts longer: Data stored on non-volatile flash RAM (USB stick or SD cards?), optical media (CD, DVD, or Blu-Ray?), or magnetic disk (floppies, hard drives?) My gut tells me optical media, but I'm not sure. Furthermore, which of those digital media would be most suitable for long-term data storage where environmental issues are unknown, such as low/high temperature or humidity? For example, what digital media could be stored in a basement, attic, or time capsule, and be expected to survive a reasonably long time? e.g. a lifetime, and then some. Update: Looks like optical media and magnetic tape each have one vote below. Does anybody else have an opinion or know of a study comparing the two?

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