Re: [MLUG] software raid conifg - fedora

[Shawn Parker <EMAIL:PROTECTED>]

the third drive is a recent replacement.

my previous set up was 2 80GB seagates in raid1 and a third as a
mounted backup. the mounted backup was an older drive and failed one
night. i lost all my system backups. i don't really care about losing
the backups as much as i do about losing the extra space/hardware for
backups.

the raid array was fine. i didn't lose my system or my data since the
extra drive was only a back up. but, that got me thinking about how to
set up the server differently.

when i replaced the drive, i made it a point to buy (nearly) the same
seagate model i already had so it could either be used in a raid0/5 or
as an extra drive in the raid1. this way, if another fails, i can just
swap out and buy a new drive later.

i don't think i could live without the added protection of
software/hardware raid. you don't know pain until you have to explain
to your wife that the drive holding ALL the honeymoon and wedding
pictures just failed.

:)


i'm considering the raid5 option.


On 11/11/05, George B. Robb III <EMAIL:PROTECTED> wrote:
> I have had drives fail due to lack of cooling (Two Western Digitals (120
> GB) and one Maxtor (200 Gb)  all were under warranty but, RAID saved my
> data...  For a home server either backups or RAID is a great and cheap
> way to go...  I can't agree more that mis-matched drives kill
> performance on mirrors.  DON'T use a 4200 and a 7200rpm together ;)
>
> Google search for the keywords LVM and RAID...  Loads of howtos out
> there but, everyone has their own method for establishing their disks :)
>
> George
>
>
> Mark Haidekker wrote:
>
> >On Thu November 10 2005 17:07, Dave Lloyd wrote:
> >
> >
> >>On Thu, 10 Nov 2005, Shawn Parker wrote:
> >>
> >>
> >>>when configuring a software raid in fedora core 4, how do you set up
> >>>an "extra" disk for raid1? i have 3 80GB drives in my server. i would
> >>>like to set up a raid1 (mirror) of 2 drives and use the 3rd as an
> >>>extra drive incase one fails?
> >>>
> >>>
> >
> >Yes, this is the strategy. You can set up one drive as "spare" that can be hot
> >added if another drive fails.
> >
> >
> >
> >>>how does one do this? do i configure the raid1 using all 3 drives and
> >>>simply set the "extra drive" parameter to 1? do i clone hda to hdc and
> >>>hdd so that each drive is *exactly* the same, first?
> >>>
> >>>
> >
> >The third drive should match the first two.
> >
> >
> >
> >>>i have no problem setting up a standard raid1 with just 2 drives...but
> >>>i'm a little confused when using a 3rd for an extra in fedora's
> >>>partition manager.
> >>>
> >>>
> >>Not that I have an answer, but I've got a question:  why do you want to
> >>do this?  It's my experience that the second drive will not fail until
> >>you can replace the first failed drive unless:
> >>
> >>1) There's a hardware problem where drives of a certain age fail
> >>   (mechanical, de-soldering of chips, etc.).
> >>2) Outside environmental influences.
> >>
> >>
> >
> >I would agree with that. If one drive fails, you'll realize the problem real
> >quick. There is still enough time to replace the drive before the second
> >drive also fails. I had that situation recently - the intact drive is still
> >intact. Furthermore, after drive replacement, no data was lost.
> >
> >
> >
> >>My personal opinion, and my experience backs me up here, is that
> >>operator error that causes data loss is FAR more likely than a disk
> >>failure.  You're better off doing a weekly backup to your third disk and
> >>sticking it in a file drawer than having a hot spare that can come in
> >>and replace a failed volume.
> >>
> >>
> >
> >As I mentioned above, disk failures do occur, and I had a RAID case recently.
> >I was glad I had RAID set up on that server, but I did not miss the spare
> >drive.
> >
> >IMO, if you have 3 drives, configure them as RAID5. You'll get 160 MB, 66%
> >efficiency instead of 50%.
> >
> >
> >
> >>Oh, and please, please do not mirror swap.  Mirroring really cuts write
> >>performance, and if you start to write to swap, well, things will begin
> >>to suck much more than a "normal" condition under which you write to
> >>swap.
> >>
> >>
> >
> >Right - but having one swap partition on each drive is great. Actually, some
> >people recommend RAID0 for swap to speed it up.
> >
> >Mark
> >
> >_______________________________________________
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> >
> >
> >
>
>
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--

- slp

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