Hardware Reference
In-Depth Information
Massive storage capacity
In the past, we routinely used lossy compression formats like JPEG and
MPEG to cut down file sizes. The problem with lossy compression is that,
by definition, it loses data relative to the original source format. We want
to store our digital camera images as RAW files, our camcorder video as
DV files, and our scans of old photographs as lossless TIFFs. Some of those
source formats are themselves compressed with lossy algorithms, so the
last thing we want to do is lose still more data by converting them to
something lossier still.
Modern digital AV devices produce a huge amount of data. For example,
we accumulated more than 20 GB of data just shooting RAW digital camera
images for this topic. Our SD DV camcorder records about 13.5 GB/hour. We
intend to upgrade to an HD camcorder, which boosts storage requirements
to about 40 GB/hour. (Raw HD footage can be captured at about 185 MB/
second
, if you have a drive array fast enough to keep up.) We have hundreds
of family photographic prints, some dating from the mid to late 19th cen-
tury. Scanning just one of those at high resolution may require 50 MB or
more of disk space, as may scanning just one of our 35 mm color slides or
negatives at 4,000 DPI, even using lossless compression.
And then there's our collection of ripped CD-Audio and DVD-Video discs.
All of them are stored on our media center system and we also have the
original discs, so at first glance it might seem wasteful to store copies on our
home server. But that ignores the time and effort we put in ripping all those
discs in the first place. We
really
don't want to have to re-rip hundreds and
hundreds of discs if a hard drive fails in our media center system.
In short, we have a ton of data, so we need a ton of disk space on our server.
We decided that 6 TB (6,000 GB) would suffice, at least to get started. You
might not have as much data as we do, but you probably have a lot more
than you think. Consider your own current and future storage require-
ments carefully before you configure your home server.
Data safety
We've never lost any data other than by our own stupidity, and we want
to keep it that way. Accordingly, you might expect that we'd configure our
home server with RAID storage. We didn't. Here's why.
Using RAID can increase storage performance on a heavily loaded server,
and it allows data to be recovered if a hard drive fails. Although it may
sound odd, neither of those benefits is particularly important to us. A
modern SATA hard drive is fast enough to saturate our 1000BaseT (giga-
bit) Ethernet network all by itself, so we don't need higher disk performance.
And hard drive failures are so rare that it's simply not worth worrying about
them.
Because RAID doesn't protect against the more common causes of data
loss—accidental deletion, data being corrupted by a virus or malfunction-
ing hardware, or catastrophic loss caused by theft or fire—we'd still need to
maintain backups even if we had a full RAID storage system. Given that we
back up frequently—when we're actively creating new data, we often do
