Re: Poor raid 1 performance?

In news:2xpj4ixtna3d.63e6kmv1z3h9$.dlg@xxxxxxxxxx, Gerhard Fiedler va
escriure:
> Peter wrote:
>
>> It is organized very differently. There are NO STRIPES in RAID1. On
>> each disk data seem to be organized exactly the same as on
>> standalone hard drive.
>
> Of course there are no RAID0 stripes in RAID1. But for reading, a
> stripe is nothing more than a subset of data.

The difference between RAID 0 and RAID 1 is the distance between one stripe
and the next on disk. With RAID 0, they are contiguous for both reading and
writing. With RAID 1, you cannot make them contiguous or near enough for
both writing [every sector] and reading [every two sectors].

So the obvious organisation is to make OK for writing (so just like a normal
disk), and while sequential reading you should wait while skipping the
odd-numbered sector which is in between.

There is a gain though (half traffic on the wire, for example), but I guess
media access is the bottleneck.


Antoine

.

Relevant Pages

  • Re: Raid Controllers
    ... RAID disk drives are used frequently on servers ... Level 2 stripes data at the bit level rather than the block level. ... > Level 4 -- Dedicated Parity Drive: A commonly used implementation of RAID, ...
    (microsoft.public.windowsxp.hardware)
  • Re: Poor raid 1 performance?
    ... >>> each disk data seem to be organized exactly the same as on ... > The difference between RAID 0 and RAID 1 is the distance between one stripe ... > and the next on disk. ... both drives reading sequentially. ...
    (comp.sys.ibm.pc.hardware.storage)
  • Re: Poor raid 1 performance?
    ... >>> you have the data in stripes over several disks. ... With RAID1, you have ... >> Maybe, because how data is organized on each disk, it makes difficult to ... > while reading another stripe from disk B (just like the same controller ...
    (comp.sys.ibm.pc.hardware.storage)
  • Re: Poor raid 1 performance?
    ... There are NO STRIPES in RAID1. ... >> disk data seem to be organized exactly the same as on standalone hard ... and what the controller does to speed up the reading. ...
    (comp.sys.ibm.pc.hardware.storage)
  • Re: Poor raid 1 performance?
    ... > disk data seem to be organized exactly the same as on standalone hard drive. ... Of course there are no RAID0 stripes in RAID1. ... and what the controller does to speed up the reading. ...
    (comp.sys.ibm.pc.hardware.storage)