RAID newbie...can I have several partitions on a RAID 1 array?

[Curious George]

Hello Curious George

Thanks for replying.

Well for the record I'm not a troll.

Don't bother. Every troll says they aren't one. Don't worry. I
think you sound like a newbie instead, otherwise I wouldn't be
explaining so much. Of course I do admit making such assumptions is a
character flaw of mine.

From what youve said I think youre basically saying that RAID 1 is pretty
much a waste of time unless Ive misunderstood something (quite possible).

Basically it's a waste of time, money, and effort _unless_ there is a
critical need to keep the data online and uninterrupted through sudden
catastrophic disk failure or upgrades. It is an "insurance policy"
for continuous service/uptime. It is not necessarily "more reliable"
in the sense of say MTBF, read/write verification, etc.

You haven't expounded upon why you think you need raid. So I'm trying
not to say explicitly yes or no to it. If you can make an argument
for it then FWIW, as I said before, I do think that generally one is
better off with a quality software raid than cheap PCI or ROMB RAID.
Furthermore if you really want to throw money at the reliability issue
(a la Arno) IMHO it makes more sense to look at a better controller or
better backup device rather than buy 2 cheap RAID HBAs.

I can see that if my motherboard died and I wanted to access the data on my
RAID array then I would have to replace the mobo with the same one or at
least another that had the same controller.

That is often the case, esp with (s)ATA host-based software-assisted
hardware. But sometimes the data _can_ actually be easily retrieved
with a generic HBA. I don't know if that is the case for your SI
array. Since you have it, that's easy for you to test.

Frankly if one knows what one is doing, I don't see why you would need
anything more than a disk editor to make a RAID1 disk member readable
by a generic HBA that otherwise could not.

If one of the drives in the array failed then I cant see how that would be
worse than having a single stand alone drive. At least my data would be safe
on the mirrored drive How come you dont see any benefit in having a
mirrored array?

No, there are indeed benefits to raid. I use and implement it
regularly. But the benefits come with prices and the devil is in the
details.

For one thing, contrary to the theoretical ideal that ppl use to sell
raid, your data isn't always 100% safe on a mirror. True a drive can
often fail and be removed gracefully, leaving the mirrored copy up.
But occasionally a failing drive or controller can crap on the good
drive and you loose good data on both the failing and the healthy
mirror.

Another factor is the mathematical reliability of an array is
significantly less than a single drive. This occurs essentially
because it is more complex and there are more points of failure in an
array. Even though this is typically described via MTBF, which is a
problematic measurement, most ppl do not dispute the basic logic that
more complex storage has potential downsides regarding reliability.

Arrays are however sometimes described as _more_ reliable. That is
because many of these hardware problems do not affect uptime. However
it is NOT because array problems occur with lower frequency. The
array seems more reliable to the end-user because there are less
outages. However what the Administrator, the array, the wallet behind
the machine goes through behind the scenes is not factored in. Since
you are the owner and administrator, it bears looking into.

RAID protection is intended only for premature failure of redundant
parts. Lets say, for example, you buy 2 identical model drives, from
the same store and lot. You install them at the same time and due to
RAID 1 they get identical use. It would not be unreasonable to expect
that they would both die at similar times. This would not only result
in array failure if you couldn't get replacements in that small
window, but the array service life ended up being no greater than a
single drive. The devil is in the details.


So I ask the question, what about backups? Backups provide protection
from common types of loss that RAID simply can't. Backups allow you
to go back to an earlier, trusted point in time. RAID can't. Instead
Raid's advantage is graceful availability through certain hardware
problems. But this advantage is superfluous if you have ample time
windows when work or data access isn't being done or the work or data
has limited value.

Finally if we accept Arno's point that these types of low-end
controllers are prone to premature failure and are not very
compatible, the result is greater trouble, manual effort, and less
uptime compared to a single disk and a good backup. IMHO throwing a
second controller at the problem is misguided. It's poor planning and
a misallocation to buy 2 unreliable pieces of crap, because you don't
trust them, they are not intelligent enough to alert you BEFORE
failure, and you need that kind of a way out from problems because you
have bad computing practices and are not comfortable with low-level
recovery/repair.

I realise that DVD backup is vulnerable and slow as is USB HDD but given the
amount of data that many of us are having to backup this is a common method.

However being rather impatient and tired of umpteen disc changes to DVD I
bought a couple of mobile HDD racks and a couple of 250Gb HDD's. So I can
now backup to SATA HDD and swap the drives as needed - so much faster and
easier. And much cheaper than any alternative I can see.

As long as they are good racks, that works. But if you are serious
about media rotation and retention, media transportation, media
reliability, and shelf life, it actually end up not really cheaper
than some tape technologies, for example, even for smaller data sets.

 

[Gerhard Fiedler]

Frankly if one knows what one is doing, I don't see why you would need
anything more than a disk editor to make a RAID1 disk member readable
by a generic HBA that otherwise could not.

Do you have any links or other information that could help one to know what
one should be doing in such a situation?

As long as they are good racks, that works. But if you are serious
about media rotation and retention, media transportation, media
reliability, and shelf life, it actually end up not really cheaper than
some tape technologies, for example, even for smaller data sets.

Really? At least from what I remember from my last look into prices, HDDs
are so cheap that you need to have a lot of rotating media to break even
with tapes.

Gerhard

 

[willbill]

"Curious George" <[email protected]> wrote in message

From what youve said I think youre basically saying that RAID 1 is pretty
much a waste of time unless Ive misunderstood something (quite possible).

that was also the way i took it

I can see that if my motherboard died and I wanted to access the data on my
RAID array then I would have to replace the mobo with the same one or at
least another that had the same controller.

i don't know what the true odds are, but
i'll put out a guess that the odds of a working
mobo failing are 10,000 to 1 less than that
of a hard drive failing

If one of the drives in the array failed then I cant see how that would be
worse than having a single stand alone drive.

agreed

a 2 disk raid 1, with a single dead drive,
is still functional; crippled but funtional

and as long as you don't do anything stupid,
it can easily be rebuilt from the surviving
hard drive

At least my data would be safe
on the mirrored drive How come you dont see any benefit in having a
mirrored array?

I realise that DVD backup is vulnerable and slow as is USB HDD but given the
amount of data that many of us are having to backup this is a common method.

However being rather impatient and tired of umpteen disc changes to DVD I
bought a couple of mobile HDD racks and a couple of 250Gb HDD's. So I can
now backup to SATA HDD and swap the drives as needed - so much faster and
easier. And much cheaper than any alternative I can see.

fwiw, i run with a 150GB Raptor as boot drive
(3 or 4 partitions on my 2 PCs), and a large
raid 1 as my secondary data drive (simple 3114
chip on one mobo, and a separate Areca PCI-e
on the other (striped raid 1E with 3 disk array))

i back up the SATA raptor using "clone" backup
to bare IDE drives, booting from the True
Image 9.0 CD. it averages out to 2.1GB/min
to do large backups (40+ GB, i put a fan to
blow air on the exposed backup drive, and prop
it up on the side of the case with a wood rod
that is roughly 2"x2"x10"

why would anyone who has a clue buy these
slow external USB 2 boxes for backup?

i use raid 1 for the secondary drive coz i don't
have to go thru the pain of doing a backup of it
every few weeks. the boot drive is different and
i *want* offline backups for it

the key to doing offline backups is to take
the extra step of making sure that they work

bill

 

[Curious George]

Do you have any links or other information that could help one to know what
one should be doing in such a situation?

I think the best thing to do is to examine the situation before it is
up and has critical information on it. I think the simplest starting
point is to compare the beginning and ends of the disk after completed
setup on a HBA vs the raid array. It would quickly reveal what is
"special" that the host controller added and whether it is a simple
matter of delete/copy/paste or you have to manually edit.
Unfortunately my links on how to manually edit the MBR, tables, etc
are outdated. It shouldn't be hard to look up.

By now I should be a broken enough record that you know I don't get
involved with this type of scenario. But I do perform basic
backup/restore/clear functions with such editors all the time as part
of my setup/recovery safety net. In fact it has come in quite handy a
few times when moving disks around, esp a long time ago on now ancient
RAID and recovering a few failures and user screw-ups.

Really? At least from what I remember from my last look into prices, HDDs
are so cheap that you need to have a lot of rotating media to break even
with tapes.

Gerhard

Frankly, if you have a small data set, something like a DLT7000 is
dirt cheap and very reliable and reasonably quick. It's definitely
cheaper than HDDs w' racks.

Even if you need something less antiquated yes indeed the attractive
point is having lots of rotating media. The size difference between
the media tends to get lost somewhat in the rotation on smaller data
sets. HDDs are often slower than many tapes, esp for small files or
fragmented filesystems. Industrial tape also has a lower error rate
and media health is reported as part of the backup/verify process.
They are less fragile for transportation & handling including static
shock, more compact and lighter for storage, etc. Robots for smaller
capacity tapes are often on par with disk backup or having a dedicated
backup to disk machine.

In short there are many factors to consider. It isn't a clear cut
winner in all circumstances. Certainly newer drives tend to be either
be quite expensive or quite crappy and it is therefore inappropriate &
prohibitive in a lot of circumstances. But IMHO it can be appropriate
in a lot more circumstances than most ppl think esp when you star
looking closely at the dreaded concept of TCO rather than simply being
turned off by the initial expense of a new tape system from a big
retail channel.

 

[Rod Speed]

Ian R wrote

that was also the way i took it

i don't know what the true odds are, but i'll put out a guess that the odds of a working mobo
failing are 10,000 to 1 less than that of a hard drive failing

Its nowhere near that high, mainly due to the bad caps fiasco.

a 2 disk raid 1, with a single dead drive,
is still functional; crippled but funtional

and as long as you don't do anything stupid, it can easily be rebuilt from the surviving hard
drive
How come you dont see any benefit in having a mirrored array?

fwiw, i run with a 150GB Raptor as boot drive
(3 or 4 partitions on my 2 PCs), and a large
raid 1 as my secondary data drive (simple 3114
chip on one mobo, and a separate Areca PCI-e
on the other (striped raid 1E with 3 disk array))

i back up the SATA raptor using "clone" backup
to bare IDE drives, booting from the True
Image 9.0 CD. it averages out to 2.1GB/min
to do large backups (40+ GB, i put a fan to
blow air on the exposed backup drive, and prop
it up on the side of the case with a wood rod
that is roughly 2"x2"x10"

I'd do incremental backups to a SATA drive
in a removable drive bay instead myself.

why would anyone who has a clue buy these
slow external USB 2 boxes for backup?

The time doesnt matter if you arent waiting for it to happen.

i use raid 1 for the secondary drive coz i don't have to go thru the pain of doing a backup of it
every few weeks.

No real pain if you do incremental backups.

the boot drive is different and i *want* offline backups for it

the key to doing offline backups is to take
the extra step of making sure that they work

Yes, but your approach is pretty crude mechanically.

 

[Curious George]

Frankly, if you have a small data set, something like a DLT7000 is
dirt cheap and very reliable and reasonably quick. It's definitely
cheaper than HDDs w' racks.

Even if you need something less antiquated yes indeed the attractive
point is having lots of rotating media. The size difference between
the media tends to get lost somewhat in the rotation on smaller data
sets. HDDs are often slower than many tapes, esp for small files or
fragmented filesystems. Industrial tape also has a lower error rate
and media health is reported as part of the backup/verify process.
They are less fragile for transportation & handling including static
shock, more compact and lighter for storage, etc. Robots for smaller
capacity tapes are often on par with disk backup or having a dedicated
backup to disk machine.

In short there are many factors to consider. It isn't a clear cut
winner in all circumstances. Certainly newer drives tend to be either
be quite expensive or quite crappy and it is therefore inappropriate &
prohibitive in a lot of circumstances. But IMHO it can be appropriate
in a lot more circumstances than most ppl think esp when you star
looking closely at the dreaded concept of TCO rather than simply being
turned off by the initial expense of a new tape system from a big
retail channel.

You can also flick a write protect tab on an important tape. Something
you can't do with a sata disk. That's not just a feel-good thing.

With backup one has to evaluate the costs of disaster recovery if you
do *not* implement a proper backup strategy incorporating offsite
redundancy and versioning. It is not simply a matter of comparing $/
total MB storage space. Therefore also factors like track-record
start having value in the calculations. SATA simply doesn't have it
when compared to DLT, LTO, and a few others.

Don't get me wrong, there is NO _universal_best_ technology or
strategy. There's a place for disk to disk, disk to disk with tape
archival, Tape backup & archival, optical, etc. I'm just trying to
point out something less obvious to the op

 

[Arno Wagner]

Curious George wrote:

Do you have any links or other information that could help one to
know what one should be doing in such a situation?

This is nonsense. Sure, if you know the exact on-disk
layout of the old and the new controller and the exact
metadata format, no problem. Otherwise it is quite possible
that you destroy your data. And this information is _not_
publicly available.

Arno

 

[Arno Wagner]

Ian R wrote:
<big snip>


that was also the way i took it


i don't know what the true odds are, but
i'll put out a guess that the odds of a working
mobo failing are 10,000 to 1 less than that
of a hard drive failing

Make that 10:1 and it matches my experiences.

Arno

 

[willbill]

Make that 10:1 and it matches my experiences.

thank you for your input.

based on my own experience, it's
infinity to 1

my hunch is somewhere between 100:1
and 1,000:1

bill

 

[Curious George]

This is nonsense. Sure, if you know the exact on-disk
layout of the old and the new controller and the exact
metadata format, no problem. Otherwise it is quite possible
that you destroy your data. And this information is _not_
publicly available.

Arno

So then it isn't nonsense. Instead the OP is in a perfect position to
follow my advice on the new array and determine whether he can
formulate a simple disaster plan NOW.

Understand there is a big difference between reading a raid 1 mirror
on a vanilla HBA and migrating a raid1 or say raid5 array to a new,
incompatible raid controller.

 

[willbill]

I'd do incremental backups to a SATA drive
in a removable drive bay instead myself.

is this actually what you do yourself?

or is it that you are simply talking out
of your arse?

based on no (or limited) real experience?

all ears.

The time doesnt matter if you arent waiting for it to happen.

see immediately above

also external HDD boxes often have
heat issues and are almost always
a lot slower than 2.1GB/minute for
data xfer to the external backup drive,
so the time needed for the backup
*does* matter

if *you* use an external drive box
for any serious backup (say > 40GB),
what kind of xfer rate do you see???

ALL ears.

meaning that if the backup takes
100 minutes to do, or more importantly
300 to 500 minutes to do, then that
external box had better have *great*
cooling for the backup hard disk drive

No real pain if you do incremental backups.

ah

am i right in thinking that that's
all you've done for yourself this
past 3-to-5 years?

and only with a full-time *mounted*
hard drive (and not with an external
HDD box; USB2 or firewire)

right?

Yes, but your approach is pretty crude mechanically.

crude?

is "crude" a real issue for doing
backups that work?

to my mind, fast and simple
and off line and 100% are
*the* only real issues

if crude (and cheap) gives me that,
then crude (and cheap) gets my vote

all ears.

anyhow, it works 100% and averages
terrific xfer rate to the temp backup
IDE drive (generally 2.1GB/min.
with either of my current 2 PCs:
Opty 142/940, and Opty 248/940 single)

and i do a real test of it working
with some frequency

so my confidence of it working,
if/when i need it, is 99+%

i try very hard to speak from first
hand experience, and not from my arse

bill

 

[Rod Speed]

Rod Speed wrote

is this actually what you do yourself?
Yep.

or is it that you are simply talking out of your arse?
Nope.

based on no (or limited) real experience?
Nope.

all ears.

Your obscene appearance is your problem, child.

see immediately above

Completely useless, as always with your shit.

also external HDD boxes often have heat issues

Only if you're actually stupid enough to buy one that does.

And you dont have to use an external HDD box anyway.

and are almost always a lot slower than 2.1GB/
minute for data xfer to the external backup drive,
so the time needed for the backup *does* matter

Nope, not if you have enough of a clue to do incremental backups
and do the backup when you arent waiting for it to happen.

if *you* use an external drive box for any serious backup (say > 40GB), what kind of xfer rate do
you see???

Same speed as with an internal drive thanks, child.

ALL ears.

Your obscene appearance is your problem, child.

meaning that if the backup takes 100 minutes to do,

I'm not that stupid. None of my incremental backups do.

or more importantly 300 to 500 minutes to do,

That in spades.

then that external box had better have *great*
cooling for the backup hard disk drive

Not a ****ing clue, as always. And plenty of PATA
drives done the stupid way you claim to use them at
the top will get stinking hot when used like that too.

ah

Swallowed the cat have you child ?

am i right in thinking that that's all you've done for yourself this past 3-to-5 years?

No, you arent right, as always. And the years are
irrelevant to what is being discussed NOW anyway.

and only with a full-time *mounted* hard drive (and not with an external HDD box; USB2 or
firewire)

right?

Wrong, as always.

crude?

****ing crude.

is "crude" a real issue for doing backups that work?

Yep, most obviously when the drive gets knocked
off onto the floor when that stupid approach is used.

to my mind,

Not a shred of evidence of any mind, just ear to ear dog shit.

fast and simple and off line and 100% are *the* only real issues

More fool you.

if crude (and cheap) gives me that,
then crude (and cheap) gets my vote

More fool you.

all ears.

Your obscene appearance is your problem, child.

anyhow, it works 100% and averages
terrific xfer rate to the temp backup
IDE drive (generally 2.1GB/min.
with either of my current 2 PCs:
Opty 142/940, and Opty 248/940 single)

Irrelevant if you haven enough of a clue to do incremental
backups and enough of a clue to do then when you arent
waiting for them to complete in spades.

and i do a real test of it working with some frequency

Well whoopy ****ing do, child.

so my confidence of it working, if/when i need it, is 99+%

Mine is 100% thanks.

i try very hard to speak from first hand experience, and not from my arse

Try harder, child.

 

[willbill]

Mine is 100% thanks.

few things are 100%

the fact that you say that should
give anyone here more than a clue
about you

my strong hunch is that you've
never tested it, which means
it may well be 0%

i am also questioning how much of
any large backup you've ever done.
meaning that you have no real clue
as to real data xfer rates with
large backups
-----

why do you post on this n/g?

as far as i can tell, you have a huge
amount of bias, which is what you
offer to us with great frequency,
and very little meaningful experiance

which is why i kill filed you in
my Agent n/g program on all n/g's
(one of only two that i've ever
kill filed), close to a year ago

i've never kill filed anyone from
my Mozilla n/g reader/posting,
which is why i still see/respond
to you

as far as i can tell, you are
pretty doggone stupid

bill

Strange as it may seem, no amount of
learning can cure stupidity, and formal
education positively fortifies it.

Stephen Vizinczey

 

[Rod Speed]

Rod Speed wrote

few things are 100%

Duh. This one is one of them tho.

the fact that you say that should give anyone here more than a clue about you

Never ever could bullshit its way out of a wet paper bag.

my strong hunch is that you've never tested it,

Guess which pathetic little pig ignorant fool has just
got egg all over its pathetic little face, yet again ?

which means it may well be 0%

Thanks for that completely superfluous proof that you have
never ever had a ****ing clue about anything at all, ever.

i am also questioning how much of any large backup you've ever done.

You have always been, and always will be, completely and utterly irrelevant.

What you might or might not claim to 'question' in spades.

meaning that you have no real clue as to real data xfer rates with large backups

Guess which pathetic little pig ignorant fool has just
got egg all over its pathetic little face, yet again ?

And I rubbed your stupid little pig ignorant nose in the FACT
that anyone with a clue uses incremental backups and isnt
stupid enough to sit there while the backup is done too.

-----

why do you post on this n/g?

Because I feel like doing that thanks, child.

as far as i can tell, you have a huge amount of bias, which is what you offer to us with great
frequency,

Just how many of you are there between those ears, child ?

and very little meaningful experiance

Or I might well have been doing it since
before you were even born thanks child.

which is why i kill filed you in my Agent n/g program on all n/g's (one of only two that i've ever
kill filed), close to a year ago

You have always been, and always will be, completely and utterly irrelevant.

What you might or might not claim to read in spades.

i've never kill filed anyone from my Mozilla n/g reader/posting, which is why i still see/respond
to you

You have always been, and always will be, completely and utterly irrelevant.

What you might or might not claim to read in spades.

as far as i can tell, you are pretty doggone stupid

Any 2 year old could leave that for dead, child.

bill

Strange as it may seem, no amount of learning can cure stupidity, and formal education positively
fortifies it.

Stephen Vizinczey

Never ever could bullshit its way out of a wet paper bag.

 

[willbill]

Duh. This one is one of them tho.


Never ever could bullshit its way out of a wet paper bag.


Guess which pathetic little pig ignorant fool has just
got egg all over its pathetic little face, yet again ?

<snip>

foul language like this and *especially*
little useful content are why i kill filed
you on my primary Agent n/g reader

you clearly have serious mental problems

i suggest to others that they kill file you

bill

 

[Rod Speed]

Rod Speed wrote

foul language like this

You wouldnt know what foul language was if it bit you on your lard arse, child.

and *especially* little useful content

Never ever could bullshit its way out of a wet paper bag.

are why i kill filed you on my primary Agent n/g reader

You have always been, and always will be, completely and utterly irrelevant.

What you might or might not claim to read in spades.

you clearly have serious mental problems

Never ever could bullshit its way out of a wet paper bag.

i suggest to others that they kill file you

You have always been, and always will be, completely and utterly irrelevant.

What you might or might not suggest in spades.