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RAID Question
OK been reading about RAID https://en.wikipedia.org/wiki/Standard_RAID_levels
A statement confused me: “For reads and writes that are larger than the stripe size, such as copying files or video playback, the disks will be seeking to the same position on each disk, so the seek time of the array will be the same as that of a single drive. For reads and writes that are smaller than the stripe size, such as database access, the drives will be able to seek independently.”
I know this may seem simple to some, but can someone explain to me in Laymans terms how something like FCP7 is actually faster on a RAID0? Because its primarily video playback and rendering performance which is needed right? And if the above’s true….Im confused :S
😀
Tom Morter-Laing
Freelance Editor,
Certified Apple Product Proffessional, 2010
http://www.depictproductions.co.ukSony Z5, with Rode NTG2.
iMac 27″ intel i7 2.93GHz, 12GB RAM, ATI HD5750 [1GB GDDR5], 2TB Int. SATA with 2TB External HDD; (FW800), with Elgato Turbo H264HD. -
8 Replies
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IMO that’s a confusing way of putting it as seek time is only part of the performance equation.
When a file is saved on striped drives it’s split into blocks and those blocks are recorded alternately on the drives.
The “stripe size” is the size of those blocks.
Choosing the right stripe size for an array is a compromise – smaller size blocks are better for transfer performance but are poorer for seek times than bigger ones. So it’s possible to optimise the stripe size of an array to get better performance for either lots of little files or fewer but larger files.
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“IMO that’s a confusing way of putting it as seek time is only part of the performance equation.”
Sorry! :D:D“When a file is saved on striped drives it’s split into blocks and those blocks are recorded alternately on the drives.”
Cool so even though in some instances seek time may not be improved, its still going to be faster because of this?
Choosing the right stripe size for an array is a compromise – smaller size blocks are better for transfer performance but are poorer for seek times than bigger ones. So it’s possible to optimise the stripe size of an array to get better performance for either lots of little files or fewer but larger files.
Cool- OK so possibly a tricky question, but is there an optimum/ recommended size for a FCP video editor? And will it generally always be faster anyway (than a standard drive)?
Incidentally, do you know how this is controlled? Ie in Disk Utility? And what about something like a G-Tech G-Raid where its already set up, is there a way of setting it up to be better?
——Further apologies for stupidity, RAID is something Im still trying to get my head around completely- I understand it’s uses, but not the specifics of the technology.
😀
Tom Morter-Laing
Freelance Editor,
Certified Apple Product Proffessional, 2010
http://www.depictproductions.co.ukSony Z5, with Rode NTG2.
iMac 27″ intel i7 2.93GHz, 12GB RAM, ATI HD5750 [1GB GDDR5], 2TB Int. SATA with 2TB External HDD; (FW800), with Elgato Turbo H264HD. -
“Cool so even though in some instances seek time may not be improved, its still going to be faster because of this?”
In my experience, yes
“is there an optimum/ recommended size for a FCP video editor?”
I don’t know of one. Others might know better than me though.
“do you know how this is controlled? Ie in Disk Utility? And what about something like a G-Tech G-Raid where its already set up, is there a way of setting it up to be better?”
I think that depends on what kind of Raid controller card the drives are attached to. Disk Utility does have a Raid option but I’d expect that if you were using a third party Raid that was already set up, you’d have to have a utility that’s specific to that.
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[Thomas Morter-Laing] “is there an optimum/ recommended size for a FCP video editor? And will it generally always be faster anyway (than a standard drive)?”
The RAID systems that are primarily designed for editing come optimized from the factory. They come ready to go, right of the box, with the right controller and the right drives. The user configured systems are less expensive, but installation and configuration are hardly ever as seamless.
[Thomas Morter-Laing] “how this is controlled? Ie in Disk Utility? And what about something like a G-Tech G-Raid where its already set up, is there a way of setting it up to be better?
“The better RAID systems are 100% hardware RAIDs, not controlled by software such as Disk Utility. Read my reviews of the CalDigit HDOne and HDPro2 RAIDs in the Cow library for a thorough explanation – I go into detail on the differences in hardware and software RAIDs, and several other factors, which you will want to know about.
David Roth Weiss
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David Weiss Productions, Inc.
Los Angeles
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I have a CineRAID (8TB mini-SAS RAID5) with an Areca controller card, and Areca had recommended to me a stripe size of 128KB for video editing, rather than the default which I think was 64KB. As has been mentioned already though, there are trade offs to bigger or smaller stripe sizes so it’s somewhat of a judgement call. With the Areca card you set the stripe size through their RAID manager interface, which is just accessed through a web browser. You won’t have control over stripe size with something like a self-contained G-RAID unit, something like that is just plug-and-play pretty much.
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Cool thanks everyone- does anyone know if there’s any Apple utilities to somehow view the hardware raid disks?
Also (I know this seems silly) but is it possible to somehow check to see information on the RAID such as the stripe size? I don’t want to control it, but I have a hardware RAID I put together myself but it sometimes takes about 15 seconds to mount on the desktop- wanna see what information I can get about it….😀
Tom Morter-Laing
Freelance Editor,
Certified Apple Product Proffessional, 2010
http://www.depictproductions.co.ukSony Z5, with Rode NTG2.
iMac 27″ intel i7 2.93GHz, 12GB RAM, ATI HD5750 [1GB GDDR5], 2TB Int. SATA with 2TB External HDD; (FW800), with Elgato Turbo H264HD. -
Sorry to kind of hijack this thread, I’ve found the info discussed here very interesting.
As I’m working on several historical projects that are getting larger and larger. I’ve been working off a small raid (LaCie) in raid 5 mode. I’m not in demand of speed, but simply redundancy. My research has led me to using raid 5 as a Widely used redundant raid mode.
I’m now needing more space as the project is growing. I’d like a 10tb raid, locally attached (no Ethernet) and speed isn’t primary concern. I’m looking at:
Drobo s
Or
G speed q
I’ve looked into sonnet, but these are the 2 I’m most intrigued by. Any others I should be considering? Is raid 5 appropriate? I don’t need crazy redundancy, just reasonable.
Thanks…
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I second this request for recommendations from the cow community as well… what are people working on with Raid 6 that they like? There are reviews out there but would love some current commentary from y’all on what you like.
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