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I have a 8gb High Performance SD card that I would like to use as swap (virtual memory). Is this possible in Mac OS X Server, and if so how do I go about doing this?

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4  
May I ask why you want to do this? It seems like a horrible idea - even a high performance SD card isn't going to be as fast as a hard drive, and having a non-standard configuration that wasn't tested by Apple is just begging for trouble. – Joe Block Apr 29 '12 at 21:32
Look here: apple.stackexchange.com/a/1469/14994 – iolsmit Apr 29 '12 at 22:36
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My advice - don't do this. Even if SD card appears fast, it's when writes are aligned and full blocks. Those cards are designed to do large sequential reads/writes, in those scenario they are useless (very low IOPS with small blocks). – mspasov Jun 3 '12 at 9:44
Get an SSD for that... – Pier Apr 27 at 18:17

3 Answers

up vote 2 down vote accepted

You probably can use an SD card as a backing store.

However: you should not expect a good result. See the up-voted comments.

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up vote 0 down vote

No - the Mac OS doesn't have an accelerate feature where extra storage swaps files (or anything else for that matter). The best you could do is try to disable swap - move the swapfile directory to the card and re-start the dynamic pager.

Here are a few questions to get you started:

Also - for the purposes of VM mechanics, the server OS and the normal OS behave the same.

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I'd love to see some stats on whether this speeds things up or not. Several well respected developers have been dabbling with disabling the dynamic_pager entirely as their macs have become gunked up and slow. I don't have a good tuning guide or know if there's even a problem with the default paging setup or they have odd setups where other things are exacerbating the VM's overhead. My guess is all the new Lion things have introduced some extra complexity that can cause undesirable performance more so than in the past. Time will tell if this is so... – bmike♦ Apr 29 '12 at 22:19
I would like these details as well, as this is the motivating reason why I'm looking into doing this. – KronoS Apr 30 '12 at 4:56
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When I experimented in Mountain Lion, having swap enabled would indeed make the system faster, albeit less responsive when actually swapping as expected. – Ryccardo Apr 27 at 15:27
up vote 0 down vote

This is what I'll do.

a) Disable VM

b) Delete the original folder where the system stores swap files

c) Create a alias to a folder in the SD Card and change its name to match the folder you deleted.

d) Enable VM and see if it works, if it doesn't it PROBABLY won't crash the system, VM SHOULD simply fall back and NOT turn on.

I strongly don't recommend this, SD Card won't be any faster than HD in terms of performance.

I will recommend alias (if it works), because that way you can just delete the alias if you changed your mind.

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