Raid Card & Array Advice

Netvyper · 1 Oct 2006 at 09:36

Currently, i've ~800gb of data spread accross half a dozen drives, and its in a right mess. Additionally, I've no backup of a large portion of the data.

My plan is to shell out about £500 on a RAID5 Array, built around 320gb Seagate SATA Disks. Having not build an array on a proper scale before (only raid0 onboard stuff), Im hoping to garner some advice

What Card?
I was thinking about a 4 port card... with 4 disks, if a drive falls over, I can power down the array until i get a spare in there, its not time-critical data.
Howerver I was then thinking about expansion in future, and wondering if its possible to just add drives to a raid5 array & increase the space? so perhaps an 8 port card might work better?

The other reason for an 8 port is a hot spare, if this is a really good idea.

Basically, i need to secure my data, and improving read speeds is a bonus too. Am I going about it the right way?

rpstewart · 1 Oct 2006 at 11:57

Yeah, sounds fairly sensible. RAID5 will give you good read speed and reliabiliy but writes aren't great even with a decent card based solution but by the sound of things you're only looking for storage so no real issue.

A 4 port card might be a bit limiting in that you'll only get 960Gb with 4*320Gb disks, with 800Gb to store there's not a huge amount of headroom there. An 8 port card will give you room for expansion, most cards will support online array expansion which allows you to add another disk into the array and expand the available space (still need partition magic to do the windows side though).

Hot spares are an interesting issue, there's a good argument for using RAID6 rather than 5 if you only have one array in the machine because it gives a better failover if a drive goes than RAID5 but decent RAID6 cards start at about £500.

Netvyper · 1 Oct 2006 at 12:20

rpstewart said:
Yeah, sounds fairly sensible. RAID5 will give you good read speed and reliabiliy but writes aren't great even with a decent card based solution but by the sound of things you're only looking for storage so no real issue.

Yep, that was my thinking, its a lot of media files & so forth, so its mostly written once & left

rpstewart said:
A 4 port card might be a bit limiting in that you'll only get 960Gb with 4*320Gb disks, with 800Gb to store there's not a huge amount of headroom there. An 8 port card will give you room for expansion, most cards will support online array expansion which allows you to add another disk into the array and expand the available space (still need partition magic to do the windows side though).

Glad you said that... my maths was dodgy

Was thinking i'd come out with > 1tb... looks like definately being an 8 port card then... any recomendations on what sort of thing?
hmm, also im not a fan of partition magic, especially with that sort of data on the line, i've had one or two failures with it...
Perhaps it'll be a case of save for another couple of months and go for a full 8 disks at once...

rpstewart said:
Hot spares are an interesting issue, there's a good argument for using RAID6 rather than 5 if you only have one array in the machine because it gives a better failover if a drive goes than RAID5 but decent RAID6 cards start at about £500.

Thats a bit above my price bracket :s, I will have a look around though.

rpstewart · 1 Oct 2006 at 12:36

Netvyper said:
any recomendations on what sort of thing?

I use the 8 port RocketRaid 2320, it's a 4x PCI-e card, not bad for the money. Some other comments here

Netvyper · 1 Oct 2006 at 12:46

aye, i've been checking out the other threads around

thanks for your input

smids · 1 Oct 2006 at 13:38

Areca 1220 PCI-E card. 8 ports, does RAID 5 and 6. Costs £375 though... Still, you can get 3 smaller disks perhaps?

FAR superior to RocketRAID - this is true Hardware RAID and not software RAID like the Highpoints.

Netvyper · 1 Oct 2006 at 13:54

smids; Aye, i was looking at that... it is costly, but it should last a few (5?) years

If I get one, is it worth using the raid6? I've heard a few horror stories about raid6... (specifically an e-mail service who switched over, and had ~3 weeks downtime, rebuiling their servers from backups)

http://www.icydock.com/product/mb455spf.html <==
Any thoughts on these things?
Likely to cause more problems than they solve? or a must have for any large array?

rpstewart · 1 Oct 2006 at 14:21

smids said:
Areca 1220 PCI-E card. 8 ports, does RAID 5 and 6. Costs £375 though... Still, you can get 3 smaller disks perhaps?

FAR superior to RocketRAID - this is true Hardware RAID and not software RAID like the Highpoints.

I was always under the impression that the RocketRaids were hardware, however I've just had a wee check about and a) google suggests there's still a software component and b) a quick check on my machine shows about 20% cpu usage (of a 4400X2) when writing to disk, albeit at about 65Mb/s.

So the Areca looks nice and the price is certainly a whole lot better than it was six months ago when I was shopping for a card, the question then becomes - is it worth the £200 premium? I'd say if absolute performance is a must then yes it is otherwise I still think that the RocketRaids are worth looking at.

smids · 1 Oct 2006 at 14:24

For sure - if you cannot justify the extra £200, then don't. RocketRAID's perform admirably - but when I go out to work, I'm buying a proper hardware RAID with onboard RAM etc. The Areca is the card I'm looking at. 8 ports should do fine! Also, don't forget, a PCI-express SATA RAID card will hold its value pretty darn well.

The highpoints are only slow with RAID5 as they don't have onboard RAM (cache) and have no XOR processor which true hardware raid cards have. A proper hardware RAID card will write about 95MB/s with 3 disks and not use much, if any CPU at all.

Netvyper · 1 Oct 2006 at 15:19

well, i've looked around, and my thinking is probably towards the rocketraid...
the machine will be dedicated (or close to) simply serving files, so some CPU usage doesnt worry me. As nice as the Areca card is, It puts the array outside of my budget really

.

I assume an A64-3500 wont hit 100% when playing with a rocketraid?
any thoughts on the hot-swap bay?

smids · 1 Oct 2006 at 19:26

Netvyper said:
well, i've looked around, and my thinking is probably towards the rocketraid...
the machine will be dedicated (or close to) simply serving files, so some CPU usage doesnt worry me. As nice as the Areca card is, It puts the array outside of my budget really .

I assume an A64-3500 wont hit 100% when playing with a rocketraid?
any thoughts on the hot-swap bay?

It's not the fact that CPU usage is present - your CPU could batter out the calculations in fairness and is much more powerful than the hardware RAID XOR (parity) processors - it is the fact that this has to travel both ways down the bus and be calculated and there is no buffer on the RAID card to process ahead. It is done 'on the fly' by your CPU meaning parity data takes long to reach the disks, immensely slowing down the writes (often, onboard only hits 15MB/s writes compared with a normal (single) 7200rpm disk of about 55Mb/s). A highpoint actually accelerates this, and can hit probably about 40-50MB/s (depending on number of drives) but hardware RAID is much better and can hit probably 90MB/s+.

To be honest, I agree with you, the price is stark and pushes it out a bit - I'm personally going to bite the bullet and get the better card but then again, mine is for everyday use, and you are just using a fileserver so it should be fine. I was intending to do a RAID5 on my fileserver but then I cam to and thought, err, when am I going to need more than 30MB/s in all honesty (as I'm using RAID1 which halves the writes).

In answer to your question - about 20-25% CPU usage is all you will see absolute tops, 10-15% average.