RAID Controllers

Dempsey

I was thinking of implementing a RAID yoke on my computer, rather than back every up to CD. I would be using IDE and it will be ATA-100. Will RAID 1 give a performance increase( time accessing the hard disks reduced)?

I was looking at this controller card on komplett and wondering is it a good controller card or is it a waste of money? What should I be looking for in a RAID controller?
Will I have to use seperate IDE cables for each hard disk?

sirlinux

Raid one doesnt give you an redundancy, it gives you more performance by using two disk in parallel, it actual halfs the MTBF because there are 2 disks, so increasing the chance of failure, you wantto look at RAID 0 for redundancy. On that subject picked up a silicon image ata133 raid 0/1 controller in maplin the other day for just over €35, it's pretty good.

Dempsey

Originally posted by sirlinux
it actual halfs the MTBF because there are 2 disks, so increasing the chance of failure

Mean Time Before Failure (MTBF) of the array was reduced due to the probability of ANY one drive of the array failing. Doesnt actually mean that your hard disks are going to fail quicker.

RAID 0 offers no redundancy either.

Does RAID 5 offer a perfomance increase?

sirlinux

RAID 0 does offer redundancy, the drives are mirrored, so if one fails your data will still be intact on the other drive thats teh whole point for RAID 0!!, RAID 5 offers a huge performance boost (taking a 3 drive example), you get read and write to 2 drives simultaneously with parity going to a third drive, parity and data is spread across all 3 drives as well so redundancy is spot on. If you doing RAID 5 on IDE try go for a four channel controller, and make sure all the drives are on seperate channels, add a 4 th drive and see performance go up again.

Korg

RAID 0 (striping), is the one with no redundancy, RAID 1 (mirroring) duplicates the data across both drives. RAID 0 yields a nice performance boost, I imagine RAID 1 improves read time as well (not write tho) though i haven't tried it.

sirlinux

wops!! sorry about that, that will be me failing computer architecture then.

Korg

Didn't realise there was so many RAID levels! (here). That site answers Dempsey's original question as well. You should probably keep backing up to CD anyway, just to be really safe

whosurpaddy

whats the consensus on raid in general?
i.e. is it worth it?

a mate of mine was so proud of his ide raid system, until a few weeks ago when a power surge fecked his hdd's altogether.

i havent looked into raid properly so i dont no what level he had etc but it seems expense for nothing to me.

po0k

Is the array for home use?
Get striping (RAID level 0) with some decent drives and get some surge/spike protection for your machine (should have this anyways).

In college we're looking at RAID 3,4 or 5 in SCSI (5 36gig drives).
I'm in favour of 5 at the moment (the full list of intended uses for the machine is a bit volatile atm to say the least).

I'm hoping to build a new machine for myself oer the coming summer months, and I'm seriously cosidering RAID0 2x 120Gig UDMA133 or sATA (with pure serial drives, no parallel-to-serial converters onboard to slow things down).

Just a matter of picking the right mobo (ie most expensive version of the series).

Dempsey

I'm using this for home use. Have surge protection on modem cable and power plugs. komplett only have 2 channel ATA-100 RAID, anywhere else good for them, whats maplin like?

I assume two disks on one channel defeats the purpose of RAID?

BigEejit

With most Raid 1 setups (mirroring) there "should" be an option to turn on interleaving (I have seen it in a couple of SCSI setups, I have never laid eyes on a IDE raid setup) .. i.e. writing to one and then to the other etc, reading likewise ... gives almost as good performance as striping and of course your data is mirrored ..
The amount of data interleaved is dependent on disk buffer size and amount of that buffer set aside by the firmware for precaching etc...if you do it right its sweet

Dempsey

I will be using 120Gb 8Mb Cache WD Special Editions, so I might do that. is that called RAID 0+1?

I also spotted this on komplett but its €382.20. Anywhere cheap for RAID cards?

po0k

New mobo and/or CPU for that price tbh.
Would more than likely ahve some sort of RAID (more then liekly 0 and or 1) onboard with a few channels.

Gerry

interleaving with raid 1 will speed up read performance, but you can't interleave writes, the disks have to be written to simultaneously, and so writing will still be slower than no raid at all. But its still a big help if you want the reliability of raid 1 as you spend most of the time reading anyway.

I'm not sure about recommending raid 0, I've seen numerous people lose all their data with either a faulty drive, or a corrupted disk caused by a power failure.

If you want a really fast setup, buy a fast 10k scsi disk like the fujitsu MAM67. ( or something similar ). www.tomshardware.com and www.storagereview.com have reviews. Probably a bit pricey, but lightning fast access and transfer rates, plus quieter than a seagate barracuda ( very very quiet ). I used one for a few months in a whisper quiet dell, couldn't hear the drive even though it was right behind an open vent in the front of the pc.

BigEejit

Originally posted by Gerry
interleaving with raid 1 will speed up read performance, but you can't interleave writes, the disks have to be written to simultaneously, and so writing will still be slower than no raid at all. But its still a big help if you want the reliability of raid 1 as you spend most of the time reading anyway.

I stand corrected ww) ... I had seen the type I mentioned used in a storage array and I thought that it was common with all Raid 1 controllers

Dempsey

Originally posted by Gerry
interleaving with raid 1 will speed up read performance, but you can't interleave writes, the disks have to be written to simultaneously, and so writing will still be slower than no raid at all. But its still a big help if you want the reliability of raid 1 as you spend most of the time reading anyway.

The most resource hungry application id be doing is avi encoding, if the write time is going to be even slower, maybe I should jack the idea in?

I have 50Gb+ of stuff that took ages to do I dont want a load of cds lying around either.

Zab

I doubt your hard disk write time would be a bottleneck when you are encoding an AVI... unless you are paging heavily or using it as a scratch drive. Of course you could just get a small drive and use it for your pagefile and as a scratch drive. I don't encode AVIs myself, so do they create large temporary files or use more memory than you have in your system?

Zeb.

Dempsey

well on startup I have about 200Mb in processes running(Windows Xp) and I have 512MB altogether. I dont think that its using scratch disks or running on virtual memory.

Gerry

If you are encoding thats fine, cos thats only writing a compressed file rather slowly, as its waiting on the cpu to do all the number crunching. The lower write speed would only be an issue if you were recording uncompressed video onto the machine, say from a video capture card at full PAL resolution.