Raid Arrays

senorstealth · 20 Sep 2007 at 21:31

I have just upgraded my pc from an nforce 4 system to an intel p35 based system.
I had a raid 0 set configured, what i need to know is can i recreate this array on my new system without any data loss?

As otherwise i'm going to have big problems backing up the data

rpstewart · 20 Sep 2007 at 21:34

senorstealth said:
I have just upgraded my pc from an nforce 4 system to an intel p35 based system.
I had a raid 0 set configured, what i need to know is can i recreate this array on my new system without any data loss?

As otherwise i'm going to have big problems backing up the data

It's highly unlikely that you'll be able to transfer the array intact. You can sometimes get away with it moving between controllers from the same manufacturer but moving manufacturers hardly ever works.

Why no backups?

senorstealth · 20 Sep 2007 at 21:39

because the array is a 750gb stripe, i guess i'm going to have to rebuild the old system and back stuff up somehow

NutritioN · 17 Dec 2007 at 23:12

Damn it, just encountered the same problem. Did you have to rebuild in the end?

I've gone from ASrock ULiSATA to Asus NF4 SATA. It sees the two drives as 'free' in the config but I imagine if I move them (visually in the config) from 'free' to the 'array' it will erase them?

Also, I, erm, can't remember if they were RAID0 or 1.

Does RAID1 (mirroring) use the size of one drive and RAID0 use the total of both drives? What confused me is that it pooled the total capacity together so I was getting all 640Gb from 2*320Gb drives went I first RAIDed them on the previous MB. Didn't expect that.

Advice greatly fully recieved.

Greenlizard0 · 18 Dec 2007 at 00:44

NutritioN said:
Also, I, erm, can't remember if they were RAID0 or 1. Does RAID1 (mirroring) use the size of one drive and RAID0 use the total of both drives? What confused me is that it pooled the total capacity together so I was getting all 640Gb from 2*320Gb drives went I first RAIDed them on the previous MB. Didn't expect that.

Advice greatly fully recieved.

That'll be RAID 1.

khushy · 18 Dec 2007 at 11:46

BACKUP - BACKUP - BACKUP!!!!

Unless you are backing up to something that is useable in another system - looking at the amount of RAID0 probs recently - decision to RAID0 is just complete madness - why bother - the risks are too great???

RAID1 on an internal or RAID10 on an external controller (PCI Card etc) seems much more sensible/practical!

I know RAID0 is built for speed (that extra 1% must make all the difference LOL) - but when your system has a hissy-fit - what would you rather have - VIRTUAL speed or your important DATA intact?

Khushy

NutritioN · 18 Dec 2007 at 12:06

Greenlizard0 said:
That'll be RAID 1.

Sorry to doubt you but I did some checking and RAID0 uses the full capacity available. Which is what I had. If I had them in RAID1 then I would just have a slightly more reliable 320Gb to use rather than 640Gb.

Correct me where I'm wrong.

Ch3m1c4L · 18 Dec 2007 at 13:52

raid 0 would give 640gb raid 1 would give 320 gb with 2 320gb drives

cavemanoc · 18 Dec 2007 at 19:51

khushy said:
BACKUP - BACKUP - BACKUP!!!!

Unless you are backing up to something that is useable in another system - looking at the amount of RAID0 probs recently - decision to RAID0 is just complete madness - why bother - the risks are too great???

RAID1 on an internal or RAID10 on an external controller (PCI Card etc) seems much more sensible/practical!

I know RAID0 is built for speed (that extra 1% must make all the difference LOL) - but when your system has a hissy-fit - what would you rather have - VIRTUAL speed or your important DATA intact?

Khushy

/strokes his raid 5 array smugly

I'll take the 150% speed increase and the redundance over your Raid 1 any day

khushy · 18 Dec 2007 at 20:54

eeeeerrrrrr

actually I have a RAID10 setup - but I guess its each to their own!

khushy

LeoPheonix · 19 Dec 2007 at 16:11

changing the motherboard without rebuilding always ends in tears in my opinion. Backup system settings and data with something like Acronis and the rebuild the OS

NutritioN · 19 Dec 2007 at 16:41

yeah, plan was to try and get the hardware switch over done before christmas and have a tidy up. Then reinstall after. Now my room's going to be a tip until January.

NutritioN · 21 Dec 2007 at 22:00

Okay, put the array back into the ASRock board and now it blue screens right after the windows loading screen appears. In safe mode too.

And it's being a pain installing Windows on a spare drive on the SATA2 cable.
Never easy. When you don't have a recent backup

JBod · 21 Dec 2007 at 23:16

cavemanoc said:
/strokes his raid 5 array smugly

I'll take the 150% speed increase and the redundance over your Raid 1 any day

Depends, with a good raid controller Raid1 will be a lot faster for reads and writes. Your raid5 no matter what will be slower than his raid1 at writing due to the parity calculations that need to be done... if you gonna willy wave at least have Raid6

or some hot spares

rpstewart · 21 Dec 2007 at 23:20

JBod said:
Your raid5 no matter what will be slower than his raid1 at writing due to the parity calculations that need to be done...

No RAID1 array can write faster than a single drive - about 70-80Mb/s. With a decent RAID controller like cavemanoc's double that is easily possible with RAID5. Heck, even with a naff RAID controller like mine I can get those sort of write speeds.

JBod · 21 Dec 2007 at 23:26

rpstewart said:
No RAID1 array can write faster than a single drive - about 70-80Mb/s. With a decent RAID controller like cavemanoc's double that is easily possible with RAID5. Heck, even with a naff RAID controller like mine I can get those sort of write speeds.

Single drive? We are talking about raid here, different raid controllers distribute the data in different ways across the spindles. Also don't forget other factors such as block size.

Raid5 is slower at writing than any other Raid type other than Raid6 (double parity) its a fact of life, the parity calculations kill it in comparison to Raid1 or of course Raid0 (and the Raid10 combo). Raid4 of course is a utterly ridiculous storage method and anyone considering it should be shot

Edit: Aaaah get what you mean now, sorry read it quickly. You are saying in a pure raid1 where its just 2 drives and they are identical then the write speed is only as fast as a single disk. However the flaw is that there is no point comparing Raid1 (of two disks) to Raid5 (which is going to be more than two disks). If you are using 4+ disks and you are looking for speed then Raid10 is the only option. Raid5 is only useful as a compromise to the write speed in order to get increasingly better return of pure storage space as the quantity of spindles increases.

rpstewart · 21 Dec 2007 at 23:34

Do you actually know anything about the various RAID levels?

RAID1 mirrors data across a pair of drives. It is not capable of delivering write speeds in excess of that of a single drive and usually tends to be significantly slower.

RAID5 on a decent controller with a dedicated parity engine will write at speeds far in excess of RAID1 and pretty close to a similarly sized RAID0 array.

mk17 · 21 Dec 2007 at 23:35

I was able to move my raid 5 array from an xp32/x6800 build to v64U/Q6600 with absolutely no problems, going from AW9D-MAX to IP35-PRO - all based on a HighPoint 2310 card. No problems whatsoever, despite fears over vista and drivers.

Using mobo raid locks you in, severely.

Still necessary to backup, but that's another story.

r/w performance is tremendous, I base my SQL2K5 database on it and it flies along.

JBod · 21 Dec 2007 at 23:39

rpstewart said:
Do you actually know anything about the various RAID levels?

RAID1 mirrors data across a pair of drives. It is not capable of delivering write speeds in excess of that of a single drive and usually tends to be significantly slower.

RAID5 on a decent controller with a dedicated parity engine will write at speeds far in excess of RAID1 and pretty close to a similarly sized RAID0 array.

Read my edit, I totally misread what you put. Also on top end Raid hardware Raid5 will not reach the write speeds of Raid10 or Raid0, its simply not possible. There can be significant performance differences as well.

You will need to take into account things like read cache (controller and disk) write caching on controllers (battery backed if you please

). Some storage solutions have things like meta cache and again their own head cache for read/writes. You have your read ahead (pre-fetch) algorithms... the bells and tweaks are quite a lot these days. When you plonk a large cluster of Raid5's underneath and Raid10's you will see a significant performance difference.

cavemanoc · 22 Dec 2007 at 21:36

When(/if) I get my array back up and running I will roll out a couple of proper benchies for you. Running Raid 5 across 4 scsi's I saw no drop in performance as compared to Raid 0 - I'm sure it was there, but as the controller has a dedicated Xor calculator built into it the calculations are not a burden on the system and can be done for next to no cost.

I know my system isn't exactly the norm, and you do need to be careful when comparing it to standard stuff run off motherboards, but in my case, Raid 5 was the only way to go - and the fact that I only lose one drive to parity means I get speed and integrity at the best price <- that was the big swinger for me, scsi drives are just too damn expensive (and small) to sacrifice to raid 10

On a side note - how come raid 3 never took off - I always thought that a 9 disk array with each bit being written to a different drive (ie writing a byte at a time) with a parity on the end, making them all hot swappable (individually obv.) would be THE best solution, but performance seems to be abysmal? Seems strange to me, would have seen this as the best of all worlds.