RAID? some basic questions

i feel a little foolish asking but when i searched the forums, all the topics were way over my head...

what is RAID? what does it do? how do you use it?
If this is the kind of topic that gets posted all the time then dont bother responding too it because i know how frusturating redundant (and silly) questions are. But if anyone can direct me to, or explain briefly, some info about what RAID does and how i can use it to protect myself from losing my footage, i would really appreciate it.
thanks

[Brian M. Dickman]

Adaptec is a good source of info on what RAID is and how it works.

Here's a good summary article with a handy RAID glossary as well:

http://www.adaptec.com/worldwide/pro...d1&type=Guides

And here's a more advanced PDF that covers the topic in more depth (and has nifty graphics depicting how various RAIDs would be configured):

http://graphics.adaptec.com/pdfs/ACSP_RAID_Ch4.pdf

[Glenn Chan]

For most video uses, the only relevant level of RAID is RAID 0. http://www.acnc.com/04_01_00.html

If you do HD, SD, or some other intense format that requires large drive arrays, then RAID 0+5, 5+0, 3+0, etc. are useful. Those large files require lots of drives in an array, and RAID 0 wouldn't be a very good idea for a large array (one drive fails and the whole array goes down).

There's really not much point protecting footage, since you should be setup so that you can re-capture from your source tapes. Backup project files regularly.

[Gints Klimanis]

Glenn,

Have you ever seen any benchmarks for RAID to speed up MPEG2 file encoding from DV25 or uncompressed, or even uncompressed
file read or write? I'm interested in anything that would speed up Vegas Video 4 or Pinnacle Studio 8. As we've discussed in another thread, I'm trying to figure out if two disk RAID is worth it.
A two port IDE RAID card goes for $40 while a four port card is about $160.

[Glenn Chan]

Sorry, no idea. You could try getting a trial copy of RAM Drive software to see if that makes a difference. The software uses your RAM to make a fake and very, very fast hard drive.

[Rob Lohman]

Why would you say the only relevant level of RAID for video work
would be 0? I would think this is the least interesting level since
DV work isn't about speed. RAID is usually chosen for safety
reasons (RAID 1, 10, 5 etc.). RAID 0 striping will be interesting
for larger datarates if your doing much uncompressed work,
for example.

I highly doubt a faster harddisk or harddisk array would help
that much in speeding up MPEG2 encoding since combined
reading of DV and writing of MPEG2 is around 4 - 5 MB/s. Writing
the output MPEG2 file to ANOTHER harddisk then where you
are reading from will increase efficiency since the harddisk doesn't
have to work in more then one place at the same time.

The best performance increase for an MPEG2 encoder is more
CPU power (I'm not sure if any or how much mpeg2 encoders
are being able to take advantage of multiple processors). If
that isn't fast enough start looking into hardware MPEG encoder
boards.

See these threads for more information on RAID:
http://www.dvinfo.net/conf/showthrea...threadid=21143
http://www.dvinfo.net/conf/showthrea...threadid=20783
http://www.dvinfo.net/conf/showthrea...threadid=17404
http://www.dvinfo.net/conf/showthrea...threadid=10969
http://www.dvinfo.net/conf/showthrea...&threadid=6422

I've linked to four hardware mpeg encoders (from two manufacturers)
in this thread.

[Glenn Chan]

Why would you say the only relevant level of RAID for video work
would be 0? I would think this is the least interesting level since
DV work isn't about speed. RAID is usually chosen for safety
reasons (RAID 1, 10, 5 etc.). RAID 0 striping will be interesting
for larger datarates if your doing much uncompressed work,
for example.

Well maybe not the only relevant form of RAID, but probably the most relevant. I don't see many people using RAID 1, 3, 5, 1+0/0+1 in video work.

Some forms of RAID like 1, 3, and 5 provide data protection. Assuming you are storing video files on the drive, data protection is not as important since you have backups on your source taps. Most NLEs can re-create a project if you delete all the media, so you could simply re-capture your project.

Whether or not data protection is worth it depends on:
1- How likely your drive is to fail.
2- How much downtime (your time) costs.
3- Cost of the RAID implementation. (power supply, larger case, cooling, having enough hard drive ports, RAID controller, extra hard drives, etc.)

Considering a hard drive failure is not catastrophic, RAID probably isn't worth it compared to the costs of RAID. Compare:
change of failure X cost of failure
VS
cost of RAID
If the total costs of a RAID are $200 and the chance of the hard drive failing is 10% (probably an overestimation), then your downtime should have to cost you at least $2000. How much money do you lose having to re-capture your footage? (about 20 hours of work for ~250GB of DV, with only one system capturing)

Other data on the other hard is precious, like your project files. There are many other reasons other than hard drive failture which can cause you to lose that file, so backups are a good idea. If you do backups then the protection RAID can give isn't worth as much.

[Rob Lohman]

You have some valid points, but I just lost a 160 GB maxtor
drive within a year of buying it. It's been a real pain thus far
to get everything back. Time is gone much faster then most
people think, especially when reconstructing (how did I name
this scene file again?) etc. It's now for everybody, that's for
sure. But why would a lot of people need RAID 0 either? DV
is still only 3.5 MB/s.

In the end it all boils down to costs, how much your data is
worth to you etc. etc. Whether or not RAID is relevant and
which level to use varies from person to person in my opinion.

[Glenn Chan]

RAID 0 might be useful if you run 2 instances of Vegas? ( I have no idea if this is true )