1TB for under a grand (ex VAT)

cgarvey

I'm trying to organise 1TB RAID5, so I'm thinking of getting 7 x WD Caviar 320GB from Komplett (using 1 as a spare/hotswap), using softraid in linux, getting a fairly basic motherboard and a couple of cheap SATA PCI cards.

So I need to check that the SATA cards are OK with linux, and read up on software RAID. Reliability and data protection are my goals, rather than speed, however am I missing something by not going with hardware RAID? Hardware cards that are "deemed" any good seem to cost €300+. Anything particularly dodgy with those drives, will I get better than 36c/GB (ex VAT) anywhere close by? I had a quick look at OCUK and a couple of those UK sites I've used before, but they couldn't beat that.

What sort of power supply will I need (will be running a P4 and a DVD drive .. no other peripherals) for that many drives? I'm undecided on whether to use my current desktop or upgrade it and use the desktop (P4 2.8GHz/2GB RAM/AGP 8x with an FX5900), but I'll leave that for another day.

So anyone have any advice to offer? It'd be much appreciated!

.cg

Gone West

cgarvey wrote:

I'm trying to organise 1TB RAID5, so I'm thinking of getting 7 x WD Caviar 320GB from Komplett (using 1 as a spare/hotswap), using softraid in linux, getting a fairly basic motherboard and a couple of cheap SATA PCI cards.

So I need to check that the SATA cards are OK with linux, and read up on software RAID. Reliability and data protection are my goals, rather than speed, however am I missing something by not going with hardware RAID? Hardware cards that are "deemed" any good seem to cost €300+. Anything particularly dodgy with those drives, will I get better than 36c/GB (ex VAT) anywhere close by? I had a quick look at OCUK and a couple of those UK sites I've used before, but they couldn't beat that.

What sort of power supply will I need (will be running a P4 and a DVD drive .. no other peripherals) for that many drives? I'm undecided on whether to use my current desktop or upgrade it and use the desktop (P4 2.8GHz/2GB RAM/AGP 8x with an FX5900), but I'll leave that for another day.

So anyone have any advice to offer? It'd be much appreciated!

.cg

you will need a 550W+ go 680W to be sure.
Silly idea to go raid 5 on high end hdd's though.
Its your money.

cgarvey

Silly idea why? RAID 5 seems to be the best speed/redundancy I can afford, and I need to survive a HDD crash. Silly to go RAID at all, or just the wrong level?

.cg

Gone West

cgarvey wrote:

Silly idea why? RAID 5 seems to be the best speed/redundancy I can afford, and I need to survive a HDD crash. Silly to go RAID at all, or just the wrong level?

.cg

Assuming thats not a typo, I suggest you research the different levels of RAID.
Wikipedia has a good page on it.
Not being blase, I just dont want to see you waste money.

Also, buy your harddrives in bulk (8) from a proper retailer. They can make sure you get 8 drives from different batches (unlike komplett, which will sell you 8 drives that came out in a row.) So that they hit their lifetime bathtub curve at very different times.

cgarvey

It's not a typo, my need is to be able to survive one of my harddrives dying, hence the need for raid. I have read the wikipedia article and, like I say, 5 seems the best disk utilisation vs redundancy bang-for-buck. I'm obviously missing something? So, again, would you recommend another RAID level (given that speed isn't my primary concern)?

Care to recommend a "proper retailer"?

Ta

SickBoy

Software RAID 5 will cripple your system. It's grand for RAID 0 or 1 but when parity bits need to be calculated on the fly you're better off having a proper hardware RAID controller with a dedicated processor.
BTW you do realise that 7x320 using 1 as a hot spare gives you a total capacity of 1.6TB
ARRAY would consist of 6 member drives with the capacity of 1 member drive lost to parity and 1 hot spare.
You could get the required storage with just 4 of those 320s

cgarvey

I do realise I'm way over with my 6+1 drives, but that was coz of the savings that softraid would have given me.

I've used softraid 5 before (P4 2.6-2.8ish machine) and didn't notice it was terribly bad. I agree though, I'd be much better off (bar being tied to a specific vendor if the raid card dies) with h/w raid .. the problem is that the only recommendations I've read (for a reliable true h/w raid controller supported in linux) are well over 300 quid, and I can't find them in IE/UK anywhere (i.e. it's contact this distributor for more info type BS).

So is soft raid 5 really that slow? If so I might consider a Hardware SATA PCI card, instead of 2 of those drives. I'd prefer the space, but if there's a big difference, then that's what I'll do.

Last Q: if I do go for a decent h/w raid card, then should I be worried as to what type/speed PCI bus it uses, or are bog standard PCI buses (PCI v2.2 / 133MB/s according to my mobo manual) plenty fast for this sort of thing?

Ta for the advice.

.cg

SwampThing

Personally, I'd sarcrifice a couple of drives for a reputable RAID controller. There are a few 8-port cards out there, which will give you a bit of room for expansion, if needed later on.

Would you trust 1TB storage to software RAID - I wouldn't.

You need to weigh the effect of a disk crash versus cost - what you can afford and what you can afford to lose.

You've probably already looked - first google search - http://www.3ware.com/products/serial_ata9000.asp

Go for a good controller - if you've an issue with PCI bus bottleneck, then deal with that later.

I'm a big believer in 'do it once - do it right'

SouperComputer

Reliability and data protection are my goals, rather than speed

I would echo the sentiment form other guys here to scrap software RAID. IMO it defeats the purpose and it doesnt take too much to upset it.

Last Q: if I do go for a decent h/w raid card, then should I be worried as to what type/speed PCI bus it uses, or are bog standard PCI buses (PCI v2.2 / 133MB/s according to my mobo manual) plenty fast for this sort of thing?

Answer is yes and no. It depends on what the server is serving and to how many clients. Essentially anticipated the load on the server.

Capt'n Midnight

If it wasn't a production machine you could just get an old AT psu and use it to power some of the drives, have it switched on all the time and plug it into the mains connector on the main ATX psu - if it's one of those ATX Psu's with a power socket.

leeroybrown

I've got a lot of faith in linux software raid for RAID1 systems. They're simple, cost effective and very easy to recover. I've run loads of them without issue.

RAID5 is a different story though. I have setup a linux software RAID5 at one stage and found the performance to be adequate. My big worry was that my data would get scrubbed as the container relys on nothing going wrong on the entire system rather than just on a hardware controller. I might run one if I could put it on a well tested non-production machine that I could leave without any change/interferance and backup regularly but other than that I'd want a good hardware card.

I've also managed to scrub a test software RAID5 system with a kernel problem previously.

cgarvey

Capt'n Midnight wrote:

If it wasn't a production machine you could just get an old AT psu and use it to power some of the drives, have it switched on all the time and plug it into the mains connector on the main ATX psu - if it's one of those ATX Psu's with a power socket.

This is just to allow me have 2 cheaper, say, <400W, PSUs rather than 1 expensive 600W+, right? If so I've to get a new PSU anyway, so an extra 30+ quid, for the sake of having one, is ok by me, ta.

SouperComputer wrote:

I would echo the sentiment form other guys here to scrap software RAID. IMO it defeats the purpose and it doesnt take too much to upset it.

Hmm, I've just read the complete opposite on the ILUG archives, so they must be just implying RAID0/1 and not 5.

So then anyone recommend a PCI RAID card? The LSI one I linked to earlier is for 64bit PCI, which'd mean a new mobo as well (where as, secretly, I was hoping I could turn my current desktop setup into this raid machine, but it only has 32bit PCI). A card with linux support, that is.

Ta folks

.cg

SouperComputer

Hmm, I've just read the complete opposite on the ILUG archives, so they must be just implying RAID0/1 and not 5.

Tis up to you at the end of the day, personally I would not take an extra risk unless I needed to, but thats just me.

The LSI one I linked to earlier is for 64bit PCI, which'd mean a new mobo as well

64bit PCI is backwards compatible with 32Bit, so you can use the card no probs.

So what kind of usage is this array expected to get?

Capt'n Midnight

cgarvey wrote:

This is just to allow me have 2 cheaper, say, <400W, PSUs rather than 1 expensive 600W+, right? If so I've to get a new PSU anyway, so an extra 30+ quid, for the sake of having one, is ok by me, ta.

no it's only if you are trying to cobble something together at home for testing and you already have the PSU's lying about..

So then anyone recommend a PCI RAID card? The LSI one I linked to earlier is for 64bit PCI, which'd mean a new mobo as well (where as, secretly, I was hoping I could turn my current desktop setup into this raid machine, but it only has 32bit PCI). A card with linux support, that is.

The ideal would be a hardware raid card, many of them depend on drivers and so only work in windows cf. fakeraid. Some cards can support Hot Swap. and you would just need a lot of removable drive bays.


http://linux.yyz.us/sata/faq-sata-raid.html - "software" raid cards
http://linuxmafia.com/faq/Hardware/sata.html - some adapted cards are HW raid

http://www.tomshardware.com/2004/06/25/cheap_and_reliable_raid_5_storage_compared/page2.html

cgarvey

Cheers Capt .. If I'm going for a raid card, it will definately be a h/w one, as softraid would almost definately be better than a s/w raid card, from what I've read. I'd been using the linuxmafia link as a reference since I first started to look into this. Hadn't seen the THG review, so will chew on that for a while, ta.

.cg

QuartzIte

Trusted Reviews did an article on RAID might be of interest.

http://www.trustedreviews.com/article.aspx?art=2035