Quote:
Originally Posted by jbartlett777
With a 4 drive raid 0-1 or 3 (or 4) drive raid 5, you can enjoy increased speeds and fault tolerance in case a drive fails.
I just installed a RAID 5 on my main PC with four 250 GB drives. With a RAID 5, you loose the capacity of one drive (so the hit is smaller with more drives) but you're still up and running if a drive fails.
Read speeds are 3x faster, write speeds 2x faster.
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I think it might be important in this thread to differentiate between
faster and
higher.
RAID is
NOT faster in terms of data access. Your data is not accessed "faster", because this is a function of the drive seek times, which are not positively affected by going with RAID. In fact, drive seek times are usually a little bit slower on RAID volumes, because of the additional overhead.
Once you start copying files and such, you do begin to see the benefits of RAID. RAID arrays have
higher sustained data transfer rates for reading and writing. Different RAID types have increases in different ways. For example, RAID 1 generally has higher read transfer rates, but not higher write transfer rates. RAID 0 and 5 generally have higher read and write transfer rates.
Here is my take on this. For the purposes on Beyond TV, the sustained data transfer rate for reading TV programs or writing TV programs is VERY, VERY LOW (in the grand scheme of things). The bandwidth of the programs (even 10 simultaneous recordings) is not going to saturate the available read and/or write speeds of even a single drive. The variable that is REALLY going to affect your performance is how
quickly your data can be written or read back and how many simultaneous operations can be performed. This really depends on your
disk seek time, more than
sustained data transfer rate. (Other firmware-based technology can also help this like caching and command queuing.) This means seek times are more important (far more important) than sustained data transfer rates, so I really don't understand the over-hyped reputation for RAID in the HTPC world (as it relates to performance).
Unless you are
copying huge files, very often, you're not going to see a performance improvement. The way that BTV works, it generally does NOT do large file copying. It does file moving (which isn't affected by transfer rate, when done on the same partition) and it creates new files (like showsqueezing), but these new files are created in an incremental way and won't be done any faster if you can write 80 MB/s, compared to 40 MB/s (typical sustained transfer rates, comparing RAID 0 to a single drive.)
I do think that RAID 1 and RAID 5 are worth the hype, if drive failure is something that keeps you up at night. For me, it's just TV. If I lose it, I won't lose any sleep over it. My important files are in a different directory and I keep those backed up to another computer, but I don't feel the need to backup my TV shows and ripped DVD collection (I can always rip those again, if I had to.)
That's my two cents...
[EDIT] Here is a link to an excellent article about RAID, from StorageReview.com.
http://www.storagereview.com/guide20...epts/perf.html