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Re: [PLUG] RAID @ Home (was "Saving data from a precarious drive")
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I always though,t perhaps incorrectly that you could do a software RAID 5 with linux? Am I wrong about that, please and sincerely let me know?
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Brian Vagnoni
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From: JP Vossen [mailto:jp@jpsdomain.org]
To: plug@lists.phillylinux.org
Sent: Wed, 30 Apr 2008 16:02:51 -0400
Subject: [PLUG] RAID @ Home (was "Saving data from a precarious drive")
> Date: Wed, 30 Apr 2008 14:59:00 -0400
> From: "Brian Vagnoni" <bvagnoni@v-system.net>
> Subject: Re: [PLUG] Saving data from a precarious drive
[...]
> Consider doing raid 5 in the future on valuable data as it sure beats recovery.
You know, I used to say that too. I will not say that's wrong, because
it's not. But you know, for home or low budget use, I have some thoughts...
1) I've had two "catastrophic" disk failures where I lost the contents
of the disks in the past 8 years or so. *Both* were **caused** by my
RAID5 controller!!! (Dell CERC EIDE, i.e. rebadged Megaraid. Yes, I
know it's an el-cheapo unit. Home/low budget, remember? :)
2) Drives are so ridiculously cheap theses days that mirroring is a more
tolerable hit. As everyone on this list probably knows, RAID5 gives you
N-1 space, and mirroring gives 0.5 space. That's kind of painful to
think about, but given drive prices today, and the fact that mirroring
is just plain easier and a bit faster on writes (maybe not much, but a
little), why not?
3) Which brings me to something I hadn't originally considered. My
RAID5 drives *depend* on that CERC hardware. When that card dies (or
just flakes out), there goes the data. Say what you want about software
RAID or mirroring, I can slap software RAIDed drives into any other
machine that they will fit in and it'll probably Just Work.
4) My current mid-tower server has lots of space for drives. Some much
newer, faster, better servers I can get my hands on have space for only
two drives. No RAID5 of any kind with just 2 drives.
5) Not to mention fewer drives = less heat and power.
Having said all that, RAID of all kinds still makes sense in production,
HA, corporate settings. But put some thought into your home stuff too.
Linux software mirroring with inexpensive drives is a beautiful thing.
But you have to go a little out of your way to really duplicate both
disks, which is out-of-scope of the email but which might be an
interesting preso.
NOTE: RAID/mirroring does NOT, NOT, NOT replace backups!!! When I said
I lost the data off the drives at top, I meant what I said: "off the
drives." I had it all backed up and it was a simple matter to rebuild
the array and restore the data. I like http://backuppc.sourceforge.net/
but there's a lot of great backup software out there. See also:
http://www.backupcentral.com/.
Something to think about,
JP
PS--Yes, I know that RAID1 = Mirroring. I can just never remember if
it's RAID0 or RAID1, so I call it mirroring. See:
http://en.wikipedia.org/wiki/RAID
----------------------------|:::======|-------------------------------
JP Vossen, CISSP |:::======| jp{at}jpsdomain{dot}org
My Account, My Opinions |=========| http://www.jpsdomain.org/
----------------------------|=========|-------------------------------
"Microsoft Tax" = the additional hardware & yearly fees for the add-on
software required to protect Windows from its own poorly designed and
implemented self, while the overhead incidentally flattens Moore's Law.
___________________________________________________________________________
Philadelphia Linux Users Group -- http://www.phillylinux.org
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___________________________________________________________________________
Philadelphia Linux Users Group -- http://www.phillylinux.org
Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug
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