What's in a Typical Geek Home Network?

Mike D asks: "I have several machines on my home network (A Mac OS X server, a few Windows XP desktops, a G4 workstation, etc.) as well as various devices (wireless base stations, VPN/firewall) and always have spare machines around that I'm torn on what to do with. So, I wonder -- what do 'typical geeks' have on their home networks? What items do you feel are a requirement, what are luxuries, and what is just cool stuff that I should integrate into my own network? Of course, suggestions should be cheap/free/use existing hardware I can find around the house."

Comments

Maybe not typical

[Chess_the_cat]

But some of these will make you drool.

I've been centralizing storage, lately

[swillden]

Lots of people are listing what's on their network, so I thought I'd tell about how mine is changing, rather than what it looks like.

The biggest change of late has been driven by my decision to move my DVD and DV video onto hard disks. That decision led me to realize that 100Mbps ethernet is Just Too Slow, so I've been upgrading to GigE. That decision has made me realize that GigE can move data from machine to machine faster than the machines get get it to or from disk, which means that there is little practical advantage to local disks anymore.

And it turns out that there are significant advantages to *not* having much local storage. I haven't yet gone all the way to diskless, but I'm thinking about it.

What are the advantages of centralized storage?

• Backups are easier, because all of the important data is on one machine.
• With a big pile of disk in one place, it makes sense to use some more advaced storage management technology. In my case there are two parts to this:
  1. RAID. By using RAID I can get higher assurance for data that I care about, and I can get really fast access to data that is less important, and various levels in between.
  2. LVM. With Logical Volume Management, I can reconfigure storage on the fly, adjusting things easily, as needed, rather than having to plan things in advance. I also get the benefit of features like snapshotting, which is an instantaneous, easy way to create mini-backups. Snapshots don't replace real backups, but they're useful to enable quick recovery from mistakes.
• More effective use of the storage. With local storage, you always end up with one of two scenarios: Either the machine is constantly running out of space and you're having to clean it up, or you have vastly more room than you need. In my experience, I always ended up with a mix -- some machines were perpetually starved for space and others had oodles.
• Less concern about any given machine. If a box dies, you just fix it and put the OS back on (diskless would make this even nicer). No need to figure out how to recover data, or even restore from backup, because there's nothing of any importance on the machine.

My file server has four 200GB IDE drives, two ATA-100 and two ATA-133, each on it's own IDE controller. Each drive is carved into ten 20GB partitions. Then, each partition is joined with the corresponding partitions on the other three drives using Linux software RAID. One of these partition "sets" is mirrored -- RAID-1. On that set, a 20GB volume, I have my digital pictures and some other very important data. In order for that data to get lost, I'd have to lose all four drives. This set also gets backed up onto DVDs which are stored at my mother's house.

Two of the sets are striped -- RAID-0 -- and then combined with LVM. That gives me 160GB of very fast storage. I can get nearly 80MBps of throughput to or from logical volumes in that set. Almost enough to fill a GigE link. I use this for scratch space when editing video and the like.

The other seven partition sets are configured as RAID-5 volumes, then combined with LVM. This gives me 420GB of storage that can survive a single-disk failure and has moderate performance. I put DVD rips here, plus run the system itself out of this volume group.

That's the way it's set up now. The beauty of LVM and the many-small-partitions approach is that if I decide I want it to be different later I can fairly easily move stuff around. For example, if I wanted to add more storage to the mirrored section, taking it from the RAID-5 section, I would:

• Run "resize_reiserfs" to shrink a file system on the RAID-5 volume group.
• Run "lvreduce" to shrink the logical volume that filesystem was on.
• Run "pvmove" to tell LVM to move any data off of the particular RAID-5 set that I want to move.
• Run "vgreduce" to remove the RAID-5 set.
• Run "mdadm" twice to reconstruct the parition

Re:beware of raid on lvm

[swillden]

I'm not sure if this is just the fact that I'm unlucky or what, but RAID-on-LVM has been less than stable for me.

As Hardwyred said, you're better off reversing that and putting LVM-on-RAID. LVM expects all of its physical volumes to be present and gets very unhappy if one of them is not. Better to use RAID underneath so that what LVM sees is highly reliable volumes that work fine even when a drive kicks offline (which will happen much more often with either LVM or RAID than with just using the raw disk, since when a disk goes down Linux will try to reset it, but RAID and LVM both take that sort of failure to mean that disk is permanently offline until the sysadmin intervenes).

That said, I also thought for a while that my LVM-on-RAID setup was unstable as hell. Every time I got the system fully functional I'd get disk failures and massive file system corruption -- I was blaming reiserfs. Eventually, though, I figured out the real problem.

Power. As in, not enough of it. Apparently, my PSU could just *barely* run all four disks plus the CPU. Occasionally, though, it couldn't keep up. I hadn't worried about power because I'd had the four drives in an older box previously, and they had the same size PSU. I neglected to consider that a 1.3GHz Athlon draws more juice than a 500Mhz K6. Anyway, I finally installed a beefier (and much, much quieter) PSU and things have been running very smoothly ever since.

Not that I think that has anything to do with your situation, but it was an... interesting experience.