12 Oct 2012 etbe   » (Master)

Cheap Bulk Storage

The Problem

Some of my clients need systems that store reasonable amounts of data. This is enough data that we can expect some data corruption on disk such that traditional RAID doesn’t work, that old fashioned filesystems like Ext3/4 will have unreasonable fsck fimes, and that the number of disks in a small server isn’t enough.

NetApp is a really good option for bulk reliable storage, but their products are very expensive. BTRFS has a lot of potential, but the currently released versions (as supported in distributions such as Debian/Wheezy) lack significant features. One significant lack in current BTRFS releases is something equivalent to the ZFS send/receive functionality for remote backups, this was a major factor when I analysed the options for hard drive based backup [1], and you should always think about backup before deploying a new system. Currently ZFS is the best choice for bulk storage which is reliable if you can’t afford NetApp. Any storage system needs a minimum level of reliability if only to protect it’s own metadata and a basic RAID array doesn’t protect against media corruption with current data volumes. The combination of performance, lack of fsck (which is a performance feature), large storage support, backup, and significant real-world use makes ZFS a really good option.

Now I need to get some servers for more than 8.1TiB of storage (the capacity of a RAID-Z array of 4*3TB disks). One of my clients needs significantly more, probably at least 10 disks in a RAID-Z array so none of the cheaper servers will do.

Basically the issue that some of my clients are dealing with (and which I have to solve) is how to provide a relatively cheap ZFS system for storing reasonable amounts of data. For some systems I need to start with about 10 disks and be able to scale to 24 disks or more without excessive expense. Also to make things a little easier and cheaper 24*7 operation is not required, so instead of paying for hot-swap disks we can just schedule down-time outside business hours.

The Problem with Dell

Dell is really good for small systems, the PowerEdge tower servers that support 2*3.5″ or 4*3.5″ disks and which have space for an SSD or two are really affordable and easy to order. But even in the mid-size Dell tower servers (which are small by server standards) you have problems with just getting a few disks operating outside a RAID array [2]. The Dell online store is really great for small servers, any time I’m buying a server for less than $2500 I check the Dell online store first and usually their price is good enough that there is no need to get a quote from another company. Unfortunately all the servers with bigger storage involve disks that are unreasonably expensive (it seems that Dell makes their profit on the parts) and prices are not available online. I gave my email address and phone number to the Dell web site on Wednesday and they haven’t cared to get back to me yet. This is the type of service that makes me avoid IBM and HP for any server deployment where the Dell online store sells something suitable!

BackBlaze

For some time BackBlaze have been getting interest by describing how they store lots of data in a small amount of space by tightly stacking SATA disks. They don’t think that ZFS on Linux is ready for production, but their hardware ideas are useful. They have recently described their latest architecture [3]. They describe it as 135TB for $7,384. Of course the 135TB number is based on the idea of getting the full 3TB capacity out of each disk which they can do as they have redundancy over multiple storage pods. But anyone who wants a single fileserver needs some internal redundancy to cover disk failure. One option might be to have three RAID-Z2 arrays of 15 disks which gives a usable capacity of 42*3TB==126TB==113TiB. Note that while the ZFS documentation recommends between 3 and 9 disks per zpool for performance I don’t expect performance problems, when you only have a gigabit Ethernet connection there shouldn’t be a problem with three ZFS zpools making the network the bottleneck.

For this option the way to go would be to start with an array of 15 disks and then buy a second set of 15 disks when the first storage pool becomes full. It seems likely that 4TB disks will become cheap before a 35TiB array is filled so we can get more efficiency by delaying purchases. The BackBlaze pod isn’t cheap, they are sold as a complete system without storage disks for $US5,395 by Protocase [4]. That gives a markup of $US3,411 over the BackBlaze cost which isn’t too bad given that BackBlaze are quoting the insane bulk discount hardware prices that I could never get. Protocase also offer the case on it’s own for anyone who wants to build a system around it. It seems like the better option is to buy the system from Protocase, but that would end up being over $6,000 when Australian import duty is added and probably close to $7,000 when shipping etc is included.

Norco

Norco offers a case that takes 24 hot-swap SATA/SAS disks and a regular PC motherboard for $US399 [5]. It’s similar to the BackBlaze pod but smaller, cheaper, and there’s no obvious option to buy a configured and tested system. 24 disks would allow two RAID-Z2 arrays of 12 disks, the first array could provide 27TiB and the second array could provide something bigger when new disks are released.

SuperMicro

SuperMicro has a range of storage servers that support from 12 to 36 disks [6]. They seem good, but I’d have to deal with a reseller to buy them which would involve pain at best and at worst they wouldn’t bother getting me a quote because I only want one server at a time.

Conclusion

Does anyone know of any other options for affordable systems suitable for running ZFS on SATA disks? Preferably ones that don’t involve dealing with resellers.

At the moment it seems that the best option is to get a Norco case and build my own system as I don’t think that any of my clients needs the capacity of a BackBlaze pod at the moment. Supermicro seems good but I’d have to deal with a reseller. In my experience the difference between the resellers of such computer systems and used car dealers is that used car dealers are happy to sell one car at a time and that every used car dealer at least knows how to drive.

Also if you are an Australian reader of my blog and you want to build such storage servers to sell to my clients in Melbourne then I’d be interested to see an offer. But please make sure that any such offer includes a reference to your contributions to the Linux community if you think I won’t recognise your name. If you don’t contribute then I probably don’t want to do business with you.

As an aside, I was recently at a camera store helping a client test a new DSLR when one of the store employees started telling me how good ZFS is for storing RAW images. I totally agree that ZFS is the best filesystem for storing large RAW files and this is what I am working on right now. But it’s not the sort of advice I expect to receive at a camera store, not even one that caters to professional photographers.

Related posts:

  1. Cheap SATA Disks in a Dell PowerEdge T410 A non-profit organisation I support has just bought a Dell...
  2. ZFS vs BTRFS on Cheap Dell Servers I previously wrote about my first experiences with BTRFS [1]....
  3. Flash Storage and Servers In the comments on my post about the Dell PowerEdge...

Syndicated 2012-10-12 13:41:23 from etbe - Russell Coker

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