Expanders?

[Halk]

I'm trying to work out how to increase my storage without paying over the odds.

Currently I have 4 WD 1TB RE3 in RAID5. I'm quite short on space, so I'd like to increase that. Adding another 4 would increase it by just shy of 4TB. However once that was full I'd be pretty much stuck. The cost of a RAID card that handles more than 8 drives is a pretty large jump.

The alternative is to get 4 2TB drives. I'm thinking this is a better option because I could sell on the 1TB drives, and later add more 2TB drives.

Currently I've got an Adaptec 3805 which does the job nicely, and I've no real desire to change it in favour of anything else unless I have to.

....

All that said something else struck me. These SAS expanders that I see mentioned on specs for cards but I frankly don't have the faintest idea about. " Up to 128 SATA or SAS devices using SAS expanders scalability "

I thought initially this was some way to connect more than 8 drives with some kind of Y-splitter cable. But it seems it's nothing like that at all. Any time I search for SAS expanders I seem to get hit with tower cases and complete units rather than something simple.

Have I reached the right conclusion thinking that SAS expanders are of no interest to me?

[Particle]

I think you can get what you're after with a SAS edge expander, but they're terribly expensive. The thing is, they're generally meant to consume all of your controller's 4x links. You might spend a few hundred bucks and get a 12-port expander, but it only really nets 4 more ports over what you've got.

The best thing to do would be to go with 2TB drives before you become more heavily invested in a product that is already half as dense as the affordable high-end options. 2TB disks are only $150 and three can replace what you've got. After that it's live migration gravy if your controller has that feature.

[Molotox]

I don't know much about those cards, but I've found some *cheaper* SATA port multiplier without a case. If you could DIY the case it would come in much cheaper I think?

http://www.addonics.com/products/host_controller/ad5sapm-e.asp


Also, dunno how much use it can be to you : http://www.sata-io.org/technology/port_multipliers.asp

[Halk]

Yeah, that's eSATA though.

I was pretty sure that expanders were a dead end route. Thanks for the confirmation.

Next step is to decide which drives... I can't see past the 2TB drives, the 1TB drives would be a bad idea unless I was able to get expanders working for cheap.

I'm looking at WD 2TB RE4-GP and RE4. There's a big price jump for the non-GP version, and I can't work out why... everything seems to be the same other than (as WD would have you think) the GP is "better" with GP technology added to a RE drive. I realise that won't be the case... I'm just worried if I get GP drives I might turn around later and wish I had paid full price for the RE4s.

Other than that I don't think anyone else makes enterprise class RAID specific 2TB drives.

[Agrophel]

HP SAS Expanders cost about 190 - 225$ for 24HDD. I got HP SAS expander comming, going to use it with areca 1680.

Very good tread for HP SAS Expander: http://www.hardforum.com/showthread.php?t=1484614

HP SAS expanders use pmc sierra chip. http://www.pmc-sierra.com/products/details/pm8005/


Or can use Chenbro UEK-13601 Expander, but harder to get to work.

[Halk]

Agrophel.... Thank you very much for that link! That's how I thought expanders would work, and it's nice to see that there is a card that does it.

That opens things back up again.... I could add 12 1TB drives to get to the same position as 8 2TB. It'd be roughly the same cost. Although I'd have to find space for 16 drives. Plus it'd mean 16 drives which could mechanically fail rather than 8. Although I could go RAID6....

I think I'm still heading towards 8 2TB drives. I'm due to upgrade my case and will probably go for a MountainMods, I've not finished investigating them yet, but I suspect I'd be able to get tons of HDs in that....

Anyway. Thanks folks :)

Only thing unanswered is the RE4-GP vs RE4. I don't really care about latency and a small difference in transfer speeds.... I need to find out if there's any real difference between the drives other than this.

[Particle]

RE4-GP is not a 7200 RPM drive. For me at least, that'd be enough to kill it straight away. It is as the name suggests--it's an RE4 with "Green" line features like Intellipower. It consumes approximately half the power. (3.7W idle vs 8.1W idle, 6.8W R/W vs 10.7W R/W).

[Halk]

Yeah, that much I understand. It's actually not an issue, in fact more of a benefit. Lower heat, less power is good. Transfer speeds aren't really a big issue since it's not going to be used for anything demanding.

My problem is.... I like the enterprise raid editions, I like a reliable drive that'll last a very long time... I'm worried that RE4-GP being cheaper than RE4 means it's not as good as it in other respects (other than rotational speed/latency etc).

[Particle]

I would never feel bad about buying a WDC RE. They don't take it lightly when they call a product an enterprise class drive. The RE4 for instance is a wholly separate drive from their other lines, it's not a simple rebadge.

[josh1980]

I have had the exact same problem you had. Here's what I did...

I bought a Highpoint RocketRaid 4320 (hold 8 SAS hard drives). It has 2x4 internal links. I hooked it up to a converter that converts the internal 4x cable to an external, then ran it to this....

http://www.areca.com.tw/products/sascableexpander.htm

That SAS expander uses a 5.25" bay. Note that I do have a wire running from the back of my computer case to the front connecting to the middle front connection of the SAS expander. I have the 16 port version.

I then connected 12 1.5TB hard drives to the sas expander. It works great, except for the fact that my Seagate hard drives are not compatible with RAID, but that's my own fault according to Seagate.

Anyway, the SAS expander has firmware that does require updating on occasion. Overall the RAID card cost me about $300 (on sale on newegg every few months) and the SAS expander was about $500.

This configuration is kind of expensive, but it's a trade off between using SAS expander or a bigger RAID controller.

I run a RAID-6 across all of the drives and I typically see about 350MB/sec read and write.

Any other questions just ask :). I might have an extra RAID controller soon if you want one for cheap.

If you are looking to save a few bucks, I'd get 2TB hard drives.

Tips not entirely related to your questions:

In my personal opinion, I'd avoid Highpoint controllers like the plague. I'm having nothing but problems and they're tech support and warranty is leaving me with incompatible equipment with broken promises of firmware fixes and such. I've heard Adaptec is the most reliable although may not be the highest performing. For me, as long as the array can handle being a file server over gigabit it's fast enough for me.

Also, do NOT buy Seagate hard disks if they are not the "Enterprise" editions. They are riddled with firmware issues and my RAID array regularly freezes. This is the hard disks at fault and not the controller. Seagate will NOT help you.

I am preparing to upgrade to 16x2.5TB drives when they hit the market later this month on an Adaptec 5805 controller. Needless to say, I am going to be buying Western Digital or Hitachi for the first time in years.

[Halk]

Well, the RAID card I have is an Adaptec 3805 (2 internal 4 ports). I'm currently using Western Digital 1TB Raid Edition 3s. And I'm going to dump those in favour of 8 Western Digital Raid Edition 4 Green Power.

I decided a while back to always go enterprise, and I also decided to go for RAID drives so there's much less chance of them dropping out of an array.

8x2TB in RAID5 will do for now. If I run short of space then I'll add more. Edit : With the expander. For now the cheapest option is to go without the expander and replace the 1TB drives. That's cheaper than buying another 12 1TB drives and an expander.

Although 8 new drives leaves a lot of room for failure, so I may go RAID6... But that decision won't affect what hardware I buy.