Re: Disk Mangement Advice

Tech Tip: Click here to run a free scan for Windows Errors and optimize PC performance

From: Phillip Renouf (PhillipRenouf_at_discussions.microsoft.com)
Date: 01/06/05 

Date: Thu, 6 Jan 2005 08:27:02 -0800

I got that backwards, my appology: that'll teach me to make posts right after
coming back from vacation ;)

Writing to a RAID5 set is a much bigger performance hit than writing to a
RAID1 set. In a RAID1 set you are only writing to 2 drives, but in a RAID5
set you are writing to 3+ drives and it also has to calculate the parity
information.

Also, the n-1 does not denote that one drive holds the parity data:
effectively with a RAID5 set the available drive space is effectively equal
to n-1. The parity data is actually spread across all the drives.

Phil

"m.marien" wrote:

>
> "Phillip Renouf" <PhillipRenouf@discussions.microsoft.com> wrote in message
> news:5DA17D2B-6E6D-4CD2-839F-5BCF8527F8DE@microsoft.com...
> > Understanding that there really is no wrong way to do things, I think that
> > this is a bad idea. Running your system drive on a RAID5 array isn't a
> > great
> > option because it offers a slower Read time than a RAID1 array since in
> > RAID1
> > you are reading from 1 disk and in RAID5 you are reading from 3+ drives.
> >
>
> I think that is the whole idea. Reading from multiple drives in parallel
> moves the data n-1 times faster where n is the number of drives in the
> RAID5. It's n-1 because one of the drives just holds the parity.
>
> http://www.pcguide.com/ref/hdd/perf/raid/levels/singleLevel5-c.html
>
> You generally get better then RAID0 reading when you have more than three
> drives.
>
> RAID1 is the slowest read and write. It reads from one drive which isn't any
> better then having a single drive and has to write the data twice. Once to
> each drive. The only thing it offers is redundancy.
>
> The only problem is that you can't boot from a software RAID5, whereas you
> can from a software RAID1. With software RAID1 you are just reading from one
> drive. If you have hardware RAID, then you can boot from any RAID level, as
> the RAID looks like a single drive to the o/s.
>
>
>
>

Relevant Pages

  • Re: Very Slow deleting from USB thumb drive.
    ... Oops - I meant to give both the writing side and the deleting side of ... but I only gave the writing side. ... blocks are 1MB with today's flash memory drives. ... Thumb drives do work OK as NTFS, but I expect it would need to be ...
    (comp.sys.ibm.pc.hardware.storage)
  • Re: Disk Mangement Advice
    ... Writing to a RAID5 set is a much bigger performance hit than writing to a ... effectively with a RAID5 set the available drive space is effectively equal ... The parity data is actually spread across all the drives. ...
    (microsoft.public.windows.server.setup)
  • Re: Disk Mangement Advice
    ... Writing to a RAID5 set is a much bigger performance hit than writing to a ... effectively with a RAID5 set the available drive space is effectively equal ... The parity data is actually spread across all the drives. ...
    (microsoft.public.windows.server.networking)
  • Re: Cannot Complete the CD Writing Wizard
    ... Not familiar with CD Writing Wizard but most burning software, ... allows you to change the Temporary folder to whatever you ... up both drives' space. ...
    (microsoft.public.windowsxp.general)
  • Re: Low performance - High spec
    ... consuming the resources it should or performing as it should. ... You have multiple file (reading and writing) operations going on, so that would further limit write operation and there is also latency since the read/write head would have to move around a lot at periods in which neither reading nor writing is done. ... RAID - alternately writes to two drives at once. ...
    (microsoft.public.windows.vista.performance_maintenance)