raid on mageia

[ryk]

Hi,

i want to make a raid array on mageia2 64bit with the system on it.
The computer is an AMD A8 3870 with Gigabyte A75-D3H and 8GB RAM.
I have 3 80GB SATA disks.
M/B supports RAID 0,1,10. Ideally RAID 5 is as far as i can get, or i can find another 80GB SATA disk.
Should I format the disks using the bios utility and then install Mageia, or install Mageia and then using the software (mdadm)?
I found many how to's on internet, but i need a step-to-step procedure because i get confused with the general procedure!

THX!
Kiriakos

[wintpe]

the onboard raid as you put it, is most likly software raid (or fake raid as its sometimes called)

more info,,,,, this is a amd hudson-d3 chipset, with limited raid 0 1 10 in the chipset, so 5 will be done in the windows software driver that comes with the board.

you may also want to read this thread

http://www.linuxquestions.org/questions ... er-906462/

you can use mdadm to setup mirrored disks (for example) so that if one fails you will be protected.

This is also software raid, but supported only by the operating systems software.

I hesitate to suggest that you will find it difficalt to implement software raid, but that said I work with several SA's
and the level of understanding of software raid takes some expirience as a system administrator, especialy when things go wrong to understand.

another thing you will need to understand is that you cant boot from raid, so the boot device remains unraided with software raid. This is worked around in some cases by booting from a small partition and then starting the raid software and attaching the mirrored device as the OS starts.
But you need to create an alternative boot device for when the primary disk fails.
you also need to be able to detach and reattach a replacment device.

Raid 5 would usualy be used for a data only device, so you may boot of a mirrored pair and then use raid 5 for your home area.

None of this is a limitation when using true hardware raid.

Therefore instead (because your data is more valuable then the cost of a disk controller) I would suggest you invest in a true hardware raid controller, and a pair of decent disks (what the hell are you going to do with 80 gB disks today ).

Your board is a PCI-E so ...

3ware made some pretty good HW raid controllers, but they like many scsi and sata based raid controller manufacturers have been swallowed up by LSI.

Have a look at there website and then find an online reatiler.

but as an example a PCI-E based PC could be used with a 3ware 9650SE-2LP to mirror two 1 or 2 TB disks together.

the above raid is a true HW raid and costs about £150

replacment of failed disks is far easier for novices.

if you realy want raid 5 the the 3ware 9650SE-4LPML

as you need at least 3 disks for raid 5.

the above is about £270 and has 4 ports.

if you realy want to go the software raid way, there are several already well documented proceedures, and no need for anyone to re-write them on here for example

http://tldp.org/HOWTO/Software-RAID-HOWTO.html.

http://www.dedoimedo.com/computers/linux-raid.html

http://linuxconfig.org/Linux_Software_Raid_1_Setup

http://www.tuxradar.com/answers/280

Another option is to use veritas volume manager, im not sure if it works on mageia, but it does work on redhat enterprise so may work with mageia.

there is a free version http://www.symantec.com/storage-foundation-basic


If you cant follow that stick with my advise above, re HW raid

regards peter

[ryk]

Thanks for the reply!

The system is a simple home system. I would like to use all the hardware that i have and not buy anything new! The whole idea is faster read/write for the system files, you know, better boot time, responsive system etc.

The main problem that i see, is that the system cannot be on raid array (like you said). I was not aware of this, since in Win you can boot the raid driver in the beginning of installation and setup the system on the array.

I will think of something......

[wintpe]

re "The whole idea is faster read/write for the system files, you know, better boot time, responsive system etc."

Someone has misinformed you.

raid 5 is the slowest form of redundancy with a 3 to 5 times performance drop.

mirroring will loose you about 50% of the write performance and gain you nothing overall.

Concat stripe will improve performance, but with the risk that one disk fails you loose everything.

a mirror x mirror concat stripe is the only way to get redundancy and restore the loss of the performance from that resiliance.

If this is just a home system, I suggest you stay with one boot drive, one home drive, and then rsync home to the third drive as a backup.

this will be the easiest to setup and maintain, and perform the best

regards peter

[doktor5000]

Maybe you just want to buy an SSD? As even raid0 would give you some performance advantages, but double the chance that all your data goes boom if one drive is affected.

[wilcal]

The system is a simple home system. I would like to use all the hardware that i have and not buy anything new! The whole idea is faster read/write for the system files, you know, better boot time, responsive system etc.....

Historically RAID function is faster, more reliable
or a combination of both. Now that 128GB SSD drives
have fallen under $100 unless your doing something
BIG I see no motivation for a home RAID for speed.
Unless it's just a toy.

My video editing platform ( Intel i7 ) the boot/system
drive is a OCZ Vertex 4, 128GB drive. The data
drive is a Seagate 1TB drive. Plenty of speed
there.

If your an Ebay or Amazon then your using big
RAID 5's or such. The making professional movies
industry ( Hollywood et al ) use RAID 5/10 in
multiple racks. You do that when the talent
in front of the camera is costing you $1M/day.
That industry has traded 35mm cans of film for
roll around racks of 20,30 or 40 Seagate 1TB
drives in RAID 5/10. And two of them on set
mirrored. Doesn't seem like progress to me.

I see that Newegg is selling 30/40GB SSD drives
for around $50. IMO beats a RAID 0/1 hands down.
Use it as the boot drive.

FWIW some years ago one of my projects involved
a Mandriva Software RAID. You could set this
up in the MCC. We found it to be clumsy and
not very good at backing it up. I dunno if
that's still in there in the Mageia MCC. I
couldn't find it in Mageia 2.

[wintpe]

re Historically RAID function is faster, more reliable or a combination of both.

Im sorry, but i disagree, software raid , is never going to be faster than direct disk access.
the second part of that sentence is true ie more reliable. (less prone to loss would be better ,
as the more drives you have the increased chance a drive will fail, hence why its not a good idea to put to many disks in a raid 5 array.

Only a hardware raid can counteract the degregation in performance that having to do multiple writes causes.

a mirror has to do two writes for every block, so thats going to be 50% slower than if it does 1

a raid 5 has to calculate the xor bits and write to 3 or more disks, and on read it has to verify the checksum on the rotating block against the data parts.

All this on software raid takes CPU cycles and time, and slows performance

http://en.wikipedia.org/wiki/Standard_R ... erformance

http://en.wikipedia.org/wiki/Standard_R ... erformance

of course on hardware if we stuff enough processing power in the raid processor we can overcome this performance
from the perception of the interface,

however the fact remains that the only raid that benefits performance is concat stripe, and this has no redundancy at all.

http://en.wikipedia.org/wiki/Standard_R ... erformance

however i agree with your summing up, that an SSD is the way to go.



regards peter

[wilcal]

re Historically RAID function is faster, more reliable or a combination of both.

Im sorry, but i disagree, software raid , is never going to be faster than direct disk access.

Sorry, I was not precise enough and I agree with you. Software RAID is not
going to be faster. I was referring to hardware ( plugged into the system BUSS controller )
RAID. I've seen, and used, more then a few in my time.

[wintpe]

[wilcal]

Believe it or not, aside from SSD, the fastest hard drive
I've ever used was a 5MB, as in Five Mega Byte, 150lb
head per track monster I used in 72'. Used 6 of em,
three stacked in side by side racks. Took three men
and a boy to mount them in there. DEC BUSS. Used'em
as virtual memory for the DEC 1145's core memory
that was a whopping 48Kbytes. Even by todays standard
those huge spinning disks ( about the size of a pizza )
were really really fast. About 2ms to anything on the disk.
Cost was only about $1M each drive.

[ryk]

Thanks for the replies!

i am planning to buy 2 SSDs later this winter, but i wanted to make use of the spare 80GB sata disks.
I remember a RAID0 array which i setup back in 2006 with 2 80GB and WinXP, which was killing!!! Almost 100mb/sec!
Nowadays it seems outdated, but it still faster from any disk that i have!
That's why i think RAID10 (or 1+0) is the best solution.
Or maybe i will stick with RAID0. If a disk will blow i will loose only the operating system.....

[wintpe]

my current sandforce sata3 ssd writes at 480 meg a second and reads at 550 meg

I have a similar system to you, a phenom II 1010, on a asus crosshair V fomular

they are currently on sale at about £80.

as ive already said the raid 10 as you call it or 1 + 0 which is

mirror + mirror concat/stripe only restores the loss that the mirroring imposes so has a zero performance impact or benifit, but will eat some of your CPU cycles.

and Wilcal I used to repair 5 meg fixed 5 meg removable up/down disks of same era

once we had changed the disk we used to spin it up with the heads voicecoil disconected

and run in the platter by pushing the heads in by hand and then pulling them out and cleaning off the excess magnetic matirial.

regards peter