Re: Best Raid Level for Streaming?

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Date: Wed, 3 Mar 2004 10:33:05 -0800

Below is attached a little overview of the two that I found quite some time
ago.
Basically if you want to have your system configured for maximum streaming
potential, RAID3 is technically the way to go. I've worked with both RAID3
and RAID5 configs on high-volume streaming servers though and really found
the performance difference to be negligible. So generally I just roll with
RAID5, as it's what I'm most comfortable with.

HTH,

Jeremy

RAID 3: Striping and Parity
In RAID level 3, data is striped across a set of disks. In addition, parity
is generated and stored on a dedicated disk. With RAID 3, data chunks are
much smaller than the average I/O size and the disk spindles are
synchronized to enhance throughput in transfer rate intensive environments.
RAID 3 is well suited for CAD/CAM or imaging type applications. Since parity
is used, a RAID 3 stripe set can withstand a single disk failure without
losing data or access to data.

Advantages:
  a.. Good data availability
  b.. High performance for transfer rate intensive applications
  c.. Cost effective - only 1 extra disk is required for parity
Disadvantages:
  a.. Can satisfy only 1 I/O request at a time
  b.. Poor small, random I/O performance
  c.. Complicated

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RAID 5: Striping and Parity
In RAID level 5, both parity and data are striped across a set of disks.
Data chunks are much larger than the average I/O size. Disks are able to
satisfy requests independently which provides high read performance in a
request rate intensive environment. Since parity information is used, a RAID
5 stripe can withstand a single disk failure without losing data or access
to data.
Unfortunately, the write performance of RAID 5 is poor. Each write requires
four independent disk accesses to be completed. First old data and parity
are read off of separate disks. Next the new parity is calculated. Finally,
the new data and parity are wntten to separate disks. Many array vendors use
write caching to compensate for the poor write performance of RAID 5.
Advantages:
  a.. Average data availability
  b.. Cost effective - only 1 extra disk is required
Disadvantages:
  a.. Poor write performance
  b.. No performance gain in data transfer rate intensive applications
  c.. Complexity
  d.. Requires special hardware.
"Kevin" <anonymous@discussions.microsoft.com> wrote in message
news:57fa01c4007e$5c16bd90$a301280a@phx.gbl...
> For 300Kb/sec Files 5-60 min (5-150MB size),
> What is the best Raid Level?
> Level 5 is good for web servers of small files, but I read
> that Level 3 is best for Video Editing of huge DV files.
>
> Compressed WMV files are in between. What is recommended?
> Thanks

• Previous message: Ravi Raman: "troubleshooting"
• In reply to: Kevin: "Best Raid Level for Streaming?"
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