I'm looking for a fast RAID set to connect to a Mac Pro server. Since I'm not really a RAID expert I would like to 'hear' your opinion about a few RAID devices. My customer has no budget for a 19" RAID set like Promise VTrak, so I'm looking for a desktop-size alternative.

A few candidates that I found are:

- La Cie
- Drobo
- Promise SmartStor

- A 6-bay Promise Pegasus looks like the type of device I would prefer but that one can only be connected with Thunderbolt, which a Mac Pro doesn't support (yet?).

What device (that you have used yourself) would you recommend?

Ideally I would like to get a device with 5-6 bays, but 4 bays could be enough. The available space has to be 6 TeraByte. I read somewhere that Drobos are relatively slow, do you know if that is correct?

The connection may be FireWire 800, although I prefer eSata, but what is a good eSata card for the MacPro, and compatible with Lion Server?

asked 11/29/2011 09:27

Mac2010's gravatar image

Mac2010 ♦♦

5 Answers:
Speed is relative.  Rather than saying you need something "fast", please provide specifics.   Percentage of read vs write vs random vs sequential vs large-block (i.e, streaming video) vs transactional is a start.  How is it being used?  How are clients connecting?   What are they doing?

What sort of redundancy do you want?   (RAID5 which protects against drive failure, but has a much higher performance penalty on writes then RAID1)..

Remember performance has TWO metrics.  Access time and throughput.  If you optimize for throughput, transactional things suffer.  How many I/Os per second and what throughput do they want?  They are already a unix shop so can run iostat which reports such information.    Have them run it with 60 second sampling during a 30 minute "typical" window.  This will tell you what they are getting now, and then they can just say, we want I/Os per second to be 3X faster and/or MB/sec to be whatever.

This makes it really easy.  Then you can just make a spreadsheet,  and get the product specs for the type of operations customer does, and see which ones fit. Then you have no risk of making some sort of subjective decision on what is "best"



dlethe's gravatar image


Thanks for the advice dlethe!

> Percentage of read vs write vs random vs sequential vs large-block

Percentage is hard to tell right now. Storage will mainly be video. Clients (1 or 2) will connect over the ethernet network. There are a few other clients, office Macs, using the server (±5) but those won't need the RAID set much. We'll need to run a test to see if video editing over the network is feasible.

> How many I/Os per second and what throughput do they want?
I'll need to look into that. Right now the MacPro is a workstation; but soon we'll convert it to a server for storage only. Choosing Raid 1 or 5 will depend on performance. I see a potential bottleneck in network speed (gigabit using a fast Cisco switch) or the firewire cable. Maybe I'll need a eSata card, but I'll open another question for that issue.

What is in your experience the most likely bottleneck? As you can read, tweaking video networking is not my expertise; at least not yet...

I am aware that for best performance a dedicated RAID set over fibre channel, is (likely) the best solution but right now there is no money for high end storage equipment.

answered 2011-12-01 at 08:42:20

Mac2010's gravatar image


well, most likely bottleneck is the ethernet, by far.  for all you know, until you do some network benching, the disk is just fine..

so use netstat and jumbo frames and see if you can get around 100 mb/sec in a 1gbit ethernet, and split that accordingly between desired concurrent users and number / type od ethernet ports.  video streaming has to have well tuned networking and you have to make sure that is in order before throwing money at disks.

but ... you would consider this large block data, and raid5 would be faster then anything ... on reads.  on writes, a cheap controller like what you are looking at might give you 50 mb/sec sustained...  so find out how many MB/sec reads and writes measured at the storage and each desktop they want

answered 2011-12-02 at 07:37:33

dlethe's gravatar image


Thanks again! I'll check the things you suggest and get back at this later this week.

answered 2011-12-02 at 10:27:01

Mac2010's gravatar image


Thanks for helping me clarify this. Right now the La Cie drive seems fine and I'll see how far we get with the network speed.

answered 2011-12-02 at 12:11:46

Mac2010's gravatar image


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Asked: 11/29/2011 09:27

Seen: 187 times

Last updated: 12/08/2011 03:01