Swap and /tmp - SSD vs RAID 0

[atkinsr]

First off... Hi everybody! I found this site when searching for an answer to the below question. Hopefully somebody can help.

I'm putting together my first Mac. It's pretty much a beast as I'll be using it for audio (Cubase 5 with a lot of VSTs and up to 24 channels at once) and video editing (Final Cut - a lot of HD, some uncompressed), as well as generic family photoshop stuff.

It's (probably) a pretty typical configuration for us not-quite-rich and missing-mortgage-payments to-pay-for-this-ourselves types:

An early 2008 2.8 dual quad core mac pro with 18GB of memory. It will have an 80GB Intel X25-m SSD boot/application disk with 4 Seagate 7200.11 1.5TB disks in RAID 0/stripe (so it's all internal) for data using the OS for RAID, and of course dual external drives for time capsule backups (4 disks striped without any mirroring is risky!) with the original 340GB drive used for Carbon Copy images of the SSD (yes, I'm paranoid - rightfully so, long story)

I would like to know if the SSD or the 4 disk stripe is the best option for swap and /tmp performance.

I'm a little concerned about wear on the SSD (if that is the better solution). My (very limited) understanding of SSDs is that the cells do wear out. While this may not be an issue for simple boot/app drives which are (relative to swap) infrequently accessed, it could be a serious one for something that gets as much I/O as swap.

I'm also curious about the difference in performance between system/OS RAID 0 and hardware RAID 0.
I don't think I'll be maxing out all 8 cores for a while, but how does it compare with say 4 free cores vs a RocketRaid card?


If you have pointers to benchmarks and/or real life experience with these various configs, please reply.

Thank you in advance for your help!

 

[jdmlight]

I would like to know if the SSD or the 4 disk stripe is the best option for swap and /tmp performance.

Probably your best bet for performance would be on the 4 disk stripe. Also you then wouldn't have to be as concerned about excessive writes on your SSD. (although the Intel SSDs are supposed to have wear leveling to help prevent one spot in the memory from getting worn out)

I'm also curious about the difference in performance between system/OS RAID 0 and hardware RAID 0.

A quick Google search () found this:
http://www.xlr8yourmac.com/OSX/OSX_RAIDvsIDE_Card_RAID.html
A slightly outdated example, but it still applies. In general, hardware RAID is faster than software RAID. But you'll still see a benefit from having a software raid over single drives.

Hardware RAID>Software RAID>Single Drive

 

[atkinsr]

Thanks for the reply, jdmlight.

I've pretty much set my mind to this config 'cause these SSDs are too expensive (still) to be wearing out.

WRT the hardware/software raid. I would agree that in general hardware raid is better. What I'm really after are recent benchmarks for RAID 0 with a similarly configured system.

Those benchmarks in that link would be useful if they were from the past year or three, but that's a G4 using ATA/133 drives. Processors and disks have gotten exponentially faster, but not at a relative (to each other) rate... so, unfortunately, it really tells me nothing.

I'll keep an eye out here, scour the raid card mfr's websites (results taken with an entire pound of salt), and if all else fails, do some testing of my own.

Thanks again!

 

[jdmlight]

do some testing of my own.

By far the most reliable benchmark. Don't install anything important (i.e. just install Mac OS X) until you find a configuration you're happy with.