Apress - Smart Home Automation with Linux (2010)- P24 ppsx

CHAPTER 3 ■ MEDIA SYSTEMS 93 ■ Note Using hardware RAID solutions is a double-edged sword for some system administrators. They work seamlessly and take no effort to set up and maintain. However, if the RAID system has a problem and uses a custom disk format, then it might be impossible to recover the data on the disk. You can solve this by buying two pieces of hardware and verifying that you can swap the disks without a problem before they are put into active service. Alternatively, you can check with the manufacturer that the disk format used either is known or comes with suitable software recovery tools. Backing up data, such as DVD or music rips, doesn’t (and shouldn’t) require RAID—although having one does no harm. Since this type of data changes less frequently, you can make do with an external USB hard drive plugged into your desktop machine. You can then run the backup software of your choice (see Chapter 6 for some possibilities here) to copy only those files that have changed and then unplug and store the drive. This prolongs the life of the drive and is worthy of the extra effort. As with all backups, they are useless unless tested regularly, so make sure that you do test them. Some people will test them by copying their backups to a new drive every 6 to 12 months. The cost is negligible, compared to the many hours spent ripping and organizing the data. Furthermore, the price per gigabyte comes down every year, allowing you store more data in a smaller form factor. If you are desperate for extra space, you can then reuse the older drive elsewhere in your system. Although tape backup systems are a favorite of most businesses, the cost and convenience of USB hard drives render them unnecessary for the home market. ■ Note Hard drives either fail in the first few weeks or the day before you remember to back up. Therefore, when buying disks, always buy from different manufacturers and at different times, so if you get one disk from a bad batch (IBM Death Star, hang your head!), you minimize your chances of getting two. Networking Considerations For the most part, the network setup of a NAS is straightforward. Usually, it will acquire its own IP through DHCP and provide access to the disk through the services of CIFS/Samba. Sometimes you will need a Microsoft Windows machine to run the setup software, but this is becoming less common as configuration is done through a web page running on the NAS. The main warning here is to look out for machines that don’t have a Samba service and instead rely on something like ZFS. ZFS is a filesystem that originated at Sun Microsystems and features on NAS systems like the Netgear SC-101. But despite the ZFS specification and its use in larger commercial systems, it does not yet have a suitable kernel driver (because of license incompatibilities). It is currently only possible to run it in conjunction with the Filesystem in Userspace (FUSE) project or the supplied closed Windows drivers. Consequently, if only a ZFS service is provided (like the aforementioned SC-101), it is necessary to install specific drivers on every device that wants to read data from the NAS. This makes it annoying for PC users and impossible for other hardware like the Squeezebox. CHAPTER 3 ■ MEDIA SYSTEMS 94 Controlling a NAS through Windows Vista can be problematic since some NAS systems use alternate authentication systems. This can be fixed with a registry hack here: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa by setting this: LmCompatibilityLevel = 1 Extra Functionality With many NAS drives being little more than embedded Linux machines, adding extra software is trivial for the manufacturer. Typical applications include the following: • Printer server • BitTorrent client • Backup support • iTunes server If you want to add your own software, then you are usually out of luck, unless you have one of the variants that has been already hacked, such as the NSLU2, or have a lot of time on your hands to discover the hack yourself! When planning a much larger home installation, then you will probably only need a very basic NAS drive, because it’s likely you’ll soon upgrade to a custom Linux server that will support all the extra functionality you can possibly throw at it, with the NAS service being available for free. When buying your first NAS, worry not about the extra functionality but of the storage space it supports because you might not have enough free space left to warrant running a BitTorrent client on it, for example. So many NAS machines are available, at fairly cheap prices, that you don’t need to worry about having everything in a single box. It is not uncommon to have one NAS with several terabytes of space for the primary media storage area for DVD and CD rips and another used as a secondary store and a function server. This second NAS then acts as a daily backup for your desktop PC and printer server. These roles allow you to power down one NAS (through X10, perhaps) for the times when it isn’t needed. NAS with Media Playback To some, this is simply a NAS with a TV-out socket on the back. To others it constitutes a paradigm shift, because it allows you to treat the unit as if it were a portable VCR and video library rolled into one. As with everything, its value is governed by how you intend to use it. One of the big selling points of these devices is that they can be moved from room to room, and even from house to house, without requiring a network. This makes it much easier to show your photographs and home videos to the ungeeked members of your family and friends because you can simply plug a media-enabled NAS device into any TV, and it will work. It is also a way of introducing (a small level) of control over what the kids are able to watch, because they’ll be limited to the contents of the hardware. CHAPTER 3 ■ MEDIA SYSTEMS 95 ■ Note There are many applications that block content for kid-safe viewing. But as parenting books tell you (or, as any parent knows), you can’t solve these problems entirely by technology because it is not really a technological problem. If you want to expand your media beyond a single room, you will need a version that supports Ethernet, such as Freecom’s MediaPlayer II or cineDISK NAS. These are combined NAS drives, supporting file sharing through Samba, and media streamers that play back files to a TV or HiFi. They have the benefit of being able to stream from a local disk, thereby eliminating any network latency and limiting the cost of separate media units such as the MediaMVP. Furthermore, by distributing your media between several of these devices, you won’t lose everything if an (unbacked up) hard drive fails. With minimal effort you can distribute the files to those machines that are more likely to play them, such as films in the living room, TV series in the bedroom, MP3s in the den, and cartoons in the kids’ room. If you are separating media in this way, be mindful of potential storage upgrades. Some devices provide a USB port for an external hard drive or memory stick (although some cheaper machines intend this for memory sticks only and do not support large disk sizes), so place these machines in rooms that are likely to increase their disk footprint the most. From personal experience, the disks holding TV shows have filled the quickest by an order of magnitude. The problem with these type of devices, like all embedded hardware, comes from their upgrade path, and not all companies will add or release new firmware with the latest codecs or fixes to old ones— and many of the devices are too new to have a hacker community to help. Also, unlike the MVPMC, there is not usually a way to use an external transcoder in this situation. Also, check the specification of each device carefully, because despite the name “NAS” appearing on the box, not all provide a network socket. Some manufacturers will claim it’s “HD-ready” when what they mean is that it will decode the files but is only capable of viewing it in standard definition. Also, many are supplied without a hard drive but will require one, even if you only intend to stream media through the network, such as with the Emprex Multimedia Player. However, it is always worth keeping an eye on the market for these devices, and they will often provide new ideas that can be implemented in software, such as the “watch YouTube on your TV” feature. Configuring a Linux Box By far the most flexible NAS server is the one you build for yourself. Any machine is suitable, since the processing power need not be great, so it can be an old laptop, Mini-ITX box, or NSLU2. The only requirement is that it has network compatibility. The optional features include USB ports (for additional drives) and a modern BIOS with 48-bit LBA so that it supports disks larger than 137.4GB. This does not just apply to internal disks, but it’s also necessary if you are using external USB hardware since they usually rely on the machine to control the disk. As ever, it is not necessary to store all your media on the one machine nor is the one machine suitable only as a file server. If you are distributing your media across different physical disks, then it is preferable to store those that necessitate higher bit rates (such as movies) on internal drives and low bit rate media (such as cartoons or music) on external drives or on slower servers. CHAPTER 3 ■ MEDIA SYSTEMS 96 Each machine needs to be set up as you saw in Chapter 1, but you need to take care with your naming convention if there are multiple servers or you’re likely to move the units. Preparing a Machine Being Linux-based, each machine will already have its own filesystem in place (including commercial devices that are based around it), so your only task here is to provide a place for your files. For internal hard drives, always create a separate ext3 partition for your media. A separate partition is used so it can mounted separately (which makes for easier recovery in case of a crash or power outage), and ext3 provides a journaling filesystem. Also, since the media partition is likely to be the first one filled, your Linux machine will not run into problems if finds there’s no more disk space left. Then provide a mount point by adding a file to /etc/fstab: /dev/sda7 /mnt/mediadisk auto user,noauto 0 0 And create hard links from somewhere more convenient; in my case, I use a root folder on the server called /media: ln /mnt/mediadisk/media/tv /media/tv Note that I have not stored files in the root of the sda7 partition but inside the media/tv folder. This conventional directory structure will benefit me later, should the disk’s purpose be extended to include extra functionality such as backups. External USB hard drives work in the same way but with a different line in /etc/fstab: /dev/sdb1 /mnt/usbdisk0 auto user,noauto 0 0 In both cases, the disks are not mounted automatically. This is a personal preference, since it requires—and requires me—to check the disks after a major power failure or crash, a step others might ignore or skip, to the detriment of the filesystem. The other change for external USB devices is that since the directories are on different physical disks, you are required to use a symlink instead: ln -s /mnt/usbdisk0/media/tv /media/tv One addition for these drives is to note which physical hard disk is used to store the content. This is for when a drive breaks, or is about to, and you need to remove the correct one. It is also helpful in those cases where two USB drives have been mounted in the reverse order. To do this, I simply change to the root directory of the drive in question and type the following: touch THIS_IS_THE_SILVER_LACIE_500G_DRIVE touch THIS_SHOULD_BE_MOUNTED_UNDER_SDB1 This demonstrates another reason for not polluting the root. If you’ve followed the tip about buying hard drives from different manufacturers, these names are easy to pick. CHAPTER 3 ■ MEDIA SYSTEMS 97 Preparing a Filesystem Once the machines are ready, the media filesystem must be considered; you must think of it in global terms across every server and across the whole house. There are three elements to the storage chain to consider: • The machine name • The machine’s physical location • The shared folder names for the media stored on that machine Taking these in order, the machine name will often be provided by the manufacturer, such as cineDISK. If you have the ability, rename it to cineDISK1, and add a sticky label to the back of the device indicating this. Always add an incrementing number to the devices if possible, because this will make scanning, backup, and maintenance scripts easier to write since each name is logically created, without arbitrary caveats. You might want to name the device without any reference to the manufacturer, as in media_nas1. This is also fine, but it’s recommended that you note to which device this refers. I use a single page on my home’s internal wiki containing all the devices, model numbers, MAC addresses, firmware versions, web forums, and so on, of each piece of hardware connected to my network. I also use this to note the physical location of each machine. The shared folder names should all follow a convention such as media_movies, media_tv, and so on. If you have kids and are providing them with access to the network, then providing separate folders such as media_kids might be an idea. The reason for splitting all the media into separate shared folders is that each can have distinct Samba access rights (each with or without passwords) and be unmounted on its own without affecting the rest of the system. It would be much harder work to control a directory of media/movies if only the root media folder was shared. Preparing a Master Server So far we have a number of servers, with lots of technical information and metadata. These names are all for the purpose of maintenance. No user would want, or should need, to know that the cartoons are on media_nas2 in the spare bedroom, under media_children. Nor should a family member be interested that you’ve split the movies folder across two separate disks 5 because there were too many for the old drive. To this end, you should designate a master server. It can be one of the media servers or an entirely different machine. It is recommended that this master server be running the most prominent and important services in the house, one that also stays on 24/7. This allows it to be used as Node0, which you’ll learn about later, in Chapter 4. This Node0 machine then mounts each shared folder, from each server, into its own directory structure. And it is this directory structure that is shared so that each media-streaming device can access the media. 5 If you’re a keen systems administrator, you can use Logical Volume Management (LVM) 2 to dynamically grow the size of partitions on your Linux system. . swap the disks without a problem before they are put into active service. Alternatively, you can check with the manufacturer that the disk format used either is known or comes with suitable. (through X10, perhaps) for the times when it isn’t needed. NAS with Media Playback To some, this is simply a NAS with a TV-out socket on the back. To others it constitutes a paradigm shift,. house, without requiring a network. This makes it much easier to show your photographs and home videos to the ungeeked members of your family and friends because you can simply plug a media-enabled