Using SSD as Swap

[lolivegarden]

Ok, this is not your usual application.

I want to know if anyone has been using SSDs specifically for swap, nothing else. Whether it be on Linux or Windows. Specifically on a SAS environment.

Even if you haven't, and you've thought about it, which Drive would you use? I know swap basically uses a lot of random writes, correct?

 

[danswartz]

Basically random workload, I'd think. On the other hand, I'm not sure the $$$ is worth it - linux AFAIK won't touch swap unless RAM is low - don't know enough about windows to comment. Unless the apps are performance critical and it's impossible to add more ram (which will likely be cheaper anyway), I'm not sure this makes a lot of sense to do...

 

[lolivegarden]

Yeah, so the applications we use can run into hundreds of GBs of ram if you let them, but sometimes you would have to change the whole servers to do that. I'm trying to investigate into using an SSD as an intermediate option.

 

[UhClem]

Ok, this is not your usual application.

I want to know if anyone has been using SSDs specifically for swap, nothing else. Whether it be on Linux or Windows. Specifically on a SAS environment.

Have you tried posting this query in the SAS forum? [Note to [H] readers: While SAS is a familiar acronym in this sub-forum, I'm quite certain the OP is referring to something completely different--a Statistical Analysis package.]

The optimal setup for performance-tuning the virtual memory usage is, first and foremost, a "software issue". For example, SAS could have very different dynamic requirements from Oracle. Also, there is the OS behavior, in the way it handles demand-paging. OP wants to specify which OS (and version) is applicable for his inquiry.

Once you can identify the characteristics of the virtual memory "traffic patterns" for your specific [SAS] application(s), you can then focus on which flavor of SSD vill best serve you. Prior to SSDs, I'm sure that SAS heavies were dedicating HDDs (maybe just outer zones) for the purpose you describe, so they would have already optimized the transition to SSDs.

Of course, maybe OP really did mean Serial Attached Scsi ...

-- UhClem

 

[parityboy]

@OP

Actually this is something I've thought about, and I plan on implementing it in my next build. My reasoning for it is simple: SSDs are far closer to DDR3 in the memory hierarchy than hard disks, and their price reflects that.

I therefore see them as more of a memory technology than a storage technology, and 256GB of SSD is far cheaper than 256GB of DDR3 last time I looked, and that doesn't include the motherboard needed to support that much memory.

For the kind of applications you seem to be talking about, I'd look at SLC SSDs, unless you consider MLC cheap enough to be a "throw away" (relative term). You may also want to look at PCIe-based SSDs rather than SATA or SAS ones, depending on the level of performance/budget you have in mind.

Since you're already using hard drives as swap, I'd personally go and buy a cheap 64GB or 128GB SATA III MLC SSD for a testbed, and see what kind of performance benefit you get, and then take it from there.

 

[lolivegarden]

Since you're already using hard drives as swap, I'd personally go and buy a cheap 64GB or 128GB SATA III MLC SSD for a testbed, and see what kind of performance benefit you get, and then take it from there.

Thanks! That's a very good suggestion.