Re: Software RAID and drive failures
On 10 Mar 2003, Ron Johnson wrote:
> On Mon, 2003-03-10 at 09:22, Kirk Strauser wrote:
> > At 2003-03-10T13:10:02Z, Ron Johnson <ron.l.johnson@cox.net> writes:
> >
> > > ?????? RAID1 can only handle 1 failure also!!
> >
> > Depends on how many drives are in the volume, doesn't it?
>
> Hmmm. By definition, RAID1 is "mirroring". Never heard of putting
> any more than 2 disks in a mirrorset. Never even thought of it,
> actually. With more than 2 disks, I'd automatically go with RAID5.
>
one approach is better than the other ... depending on the requirements
and specs and $$$ budgets
having 3 or 4 raid1 mirrored disks is good if..
( you can have as many drives in the raid1 array
( all with the same/identical data
- you can suffer 3 of 4 disk dying.. :-) and still limp along in
degraded mode ( as if it was a single non-raid disk )
- you really really cannot afford for the server to die
because of a silly disk failure ... use multiple mirrors
- and if you really really really really need to save data
and cannot afford to lose it... ( like credit card processing )
than save the data in SF, LA, NY, Miami, Dallas, etc
- raid1 does NOT protect you against "rm -rf /"
nor does it protect you against "rsync --delete"
having 4 disks in raid5...
- if you lose one disks.... you're in degraded mode..
- lose and 2nd disk ... and kiss 4 disks worth of data bye-bye
if we assuming one disk reads at 50MB/sec
than having an 2nd raid1 disks reads at an effective 100MB/sec
-- writing takes little longer to write since you have
to do lot more work on more (slow) spindles
if you want 10 disks..
first set of 5 disks .. use 4 + spare --> one raid5
second set of 5 disks . use 4 + spare --> another raid5
now raid1 both of those raid5 ... and you can read data 2x faster
-- i rather see more independent systems than number of disks
-- you need more and more disks if you are storing 100-500GB mpeg files
more raid fun...
http://www.1U-Raid5.net
8x 240GB ide disks in one 1U ???
....nah .. too much thumb twidling when it goes down
c ya
alvin
fun stuff ???
-- a disk in LA ... www1.foo.com
-- a disk in NY ... www2.foo.com
-- a disk in SF ... www3.foo.com
-- a disk in DC ... www4.foo.com
Reply to: