SSD cache drive worth it?

[Julez]

Currently I have a 640GB 7200rpm spinning disk set as my cache drive.  The only thing that I have using that cache drive are the apps, I don't have any of my video shares set to use the cache.

 

First question is would I benefit in going to like a 120gb SSD for my cache drive?

Second question if I go with the SSD would you recommend to let the video storage shares use the cache?

 

I have a small 6TB usable array that is only used to store pictures/movies.

 

I am using about half a dozen apps such as Plex Media Server and a couple others.

[sureguy]

I'd really only recommend an SSD if you are currently having issues with speed while writing to your current cache drive, or if you want to run a virtual box vm from it. 

 

You'll want a drive with good garbage collection as unraid doesn't support trim as far as I know.

 

Sent from a phone, sorry for any typos

 

 

[WeeboTech]

A benefit of having an SSD as the cache drive is not requiring a drive spinning and speed.

 

I used an SSD for my cache drive but only for apps and my home folders.

 

If I felt the need to prevent an unneeded spin up, I would have allowed my user shares to use the cache drive.

In my case, it was the requirement of instantaneous access to my home folder that necessitated the SSD on cache.

 

I like the idea of having apps and home on a drive that does not require mechanics.

Having the root on a ramdisk is one of the reasons I was attracted to unRAID from the start.

 

What ever you employ with the SSD, make sure you have a good backup strategy of the drive.

I.E. rsync the cache drive to the array somewhere on a periodic basis.

[Julez]

If all I do is have the apps utilize the cache drive, and change to an SSD, what would I see a performance increase in exactly?  I mean the performance of the apps individually are fine the way they are.  But if it somehow makes the UI or loading of a movie faster on my Roku, I'd be game for that.  Otherwise I guess I don't see the use.

[garycase]

If all I do is have the apps utilize the cache drive, and change to an SSD, what would I see a performance increase in exactly? 

 

Nobody can tell you exactly where the performance will improve;  but clearly all of your disk accesses would be significantly faster.  This doesn't help with anything you're receiving from or sending out to the network, as these are limited by network speed;  but all local processing by your applications would see a very nice "bump" in performance.

 

However, the key advantage is the elimination of a spinning drive.    If you're happy with the current performance of the system, then moving to an SSD cache isn't likely to make any real difference.

 

[Julez]

Yeah I currently don't see much if any performance problems.  I would like to see movies load quicker and be a little more responsive on fast forwarding or rewinding.  But I have a feeling to get that I just need more processing power on the client end, better use of the money would probably be spent on a Roku 3 to replace my Roku 2 .

[garycase]

Difficult to say for sure, but I'd tend to agree.    I suspect you're actually streaming the movies from the protected array -- not from the cache drive.    And if there's a transcoding step, then what you need is most likely more "horsepower" -- not a faster drive.    Note that could mean you need a better CPU on your UnRAID box ... NOT on the Roku end (unless the transcoding is done there).

 

[WeeboTech]

If all I do is have the apps utilize the cache drive, and change to an SSD, what would I see a performance increase in exactly?  I mean the performance of the apps individually are fine the way they are.  But if it somehow makes the UI or loading of a movie faster on my Roku, I'd be game for that.  Otherwise I guess I don't see the use.

 

Only if you apps that have a huge directory of small items to load. i.e. a bunch of icons or configuration files. etc, etc.

If the apps are mostly read, there's a small benefit, but not much. If I could score a small SSD at a decent price, it would be worth it in my eyes. It would eliminate a spinning drive that I could repurpose. Eliminate noise, cooling. Possibly re-use the 3.5" slot for the array. There are very cool PCI edge/slot load connectors which could allow you to use a PCI slot on the back of the computer to hold the SSD. Thus freeing up the 3.5" slot for an array drive.

 

Granted it ends up being a lil more costly, but it also serves to provide an extra slot for density.

 

http://www.newegg.com/Product/Product.aspx?Item=N82E16817998052

 

However, if you are looking for a big speed up, It's all dependent on how your apps access the SSD.

 

As I said, in my case, I redirected all my home / My Documents folder to a .home folder on the network SSD.

No spin up, instant access and all machines were able to access my documents and folders from everywhere.

Backups were incrementally maintained to the array via cron job.

[garycase]

While it's debatable whether or not an SSD really helps in terms of performance (since the write speeds are network-limited as a cache [clearly they're better for any local apps that use it);  but the lower power, no-moving-parts advantage is certainly real.    The slot-mounted 2.5" drive holders work very well, too => I've used them for both SSDs and traditional laptop drives when I didn't have other convenient mounting locations.

 

[garycase]

... one other thought:  With v5 final and the ability to use a btrfs RAID-1 fault-tolerant cache, the ultra-low-power of SSDs will be even more convenient, as you'll want 2-4 of them for the cache 

[StevenD]

Since we are talking about mounting 2.5" drives, I thought I would post this. 

 

These are actually SuperMicro 2.5" to 3.5" trays. They mount on your removable trays of SuperMicro server. Ive used them on an 826 and a 933.

 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130909414169

 

[seanant]

My take on this is cost vs. performance. How much pain can you take? 

 

Spinning disks need high bandwidth and tolerates low latency. Spinning disk is reliable, proven, and inexpensive.

 

Spinning disk has very poor latency.  Delivering high performance with spinning disk requires substantial power which means multiple spindles. The more spindles the better performance.

 

SSD has awesome  read/write performance with increased cost. Compared spindle drives SSD provides good energy efficiency.

 

Now this is the pain part. How much is a 600+ gig SSD compared to a Spindle drive?

 

If you can afford the SSD it's easy. If your thinking about selling off your personal belongings to buy a SSD then again for me another easy answer.

 

 

[WeeboTech]

While a 600+ SSD array is certainly cost debatable.

 

First question is would I benefit in going to like a 120gb SSD for my cache drive?

...

I am using about half a dozen apps such as Plex Media Server and a couple others.

 

A 120 GB one is pretty cost effective these days.

Heck, I have a 30GB one that I use for an APPS drive.

 

It all depends on how much storage you need vs the cost vs the speed.

[neilt0]

Let's say I write 5TB a month to a 128GB SSD -- so writing over the entire drive 40 times every month. How long would a mid-range SSD last?

 

I'm not that bothered if it dies after say 3 to 5 years, but if it dies in 6 or 12 months, I probably wouldn't bother.

 

Cheers,

 

Neil.

[StevenD]

Let's say I write 5TB a month to a 128GB SSD -- so writing over the entire drive 40 times every month. How long would a mid-range SSD last?

 

I'm not that bothered if it dies after say 3 to 5 years, but if it dies in 6 or 12 months, I probably wouldn't bother.

 

Cheers,

 

Neil.

 

I believe Intel and Sandisk rate theirs on "40GB of writes" per day.

[neilt0]

Let's say I write 5TB a month to a 128GB SSD -- so writing over the entire drive 40 times every month. How long would a mid-range SSD last?

 

I'm not that bothered if it dies after say 3 to 5 years, but if it dies in 6 or 12 months, I probably wouldn't bother.

 

Cheers,

 

Neil.

 

I believe Intel and Sandisk rate theirs on "40GB of writes" per day.

 

40GB of writes per day for how many years? 

[garycase]

Let's say I write 5TB a month to a 128GB SSD -- so writing over the entire drive 40 times every month. How long would a mid-range SSD last?

 

I'm not that bothered if it dies after say 3 to 5 years, but if it dies in 6 or 12 months, I probably wouldn't bother.

 

Cheers,

 

Neil.

 

5TB/month = 166 GB/day

 

Intel's endurance specifications for their 330 series drives state "... The SSD will have a minimum of three years of useful life with typical client workloads of up to 20 GB of host writes per day."

 

So your projected usage is ~ 8 times that !! 

 

Note, however, that the 500 series of Intel SSDs doubles that specification; and the 700 series has 65 times that endurance !!    This is getting significantly better with the newer NAND chips ... so it just depends on how new your SSD is.    But it's certainly true that if you use an SSD you've had a while for a cache, and are doing a significant amount of writing to the array, that you may be better off using spinning drives.    If, on the other hand, you're not actually caching your writes, but are simply using the cache for your application's storage, you're not likely to hit the write limits for several years.

 

[neilt0]

65x means in theory you could do almost 10x the theoretical 5TB a month, so the SSD could last 30 years. Or at least 3 years as it's under the duty cycle.

 

This suggest 30 years (best case scenario) -- 2,000TB written to a 100GB drive with 8k writes with 5TB written per month. I don't know what the diff is with 4k and 8k -- is that drive formatting? http://www.intel.co.uk/content/dam/www/public/us/en/documents/technology-briefs/ssd-710-series-het-brief.pdf

[jbartlett]

I have a SSD drive as one of my data drives for data that's likely to be accessed frequently (thumbnails & the like) so there's no delay caused from a drive having to spin up.

[meep]

I changed my cache drive to a SSD some time ago and have seen dramatic improvements;

 

-My Xen VMs boot and shutdown much much faster and are generally snappier in use.

 

-I've configured my 'recordings' share to use cache so PVR recordings (ArgusTV) from a VM are written first to the cache and later transferred to array via mover - I've had no issues in recording multiple simultaneous streams since installation.

 

-As a 2.5" drive, I've been able to free a 3.5" slot in my case as there's a 2.5" dedicated bracket I can now utilise

 

-I'm sure it's contributing to a cooler system as I've replaced a toasty 3.5" spinner with a much cooler SSD

 

unRaid is happily trimming the drive on a daily basis thanks to a cron job I've set up.

 

Overall, highly recommended to run an SSD as cache if you have use cases similar to my own.

 

Peter

[Leifgg]

I recently purchased and installed a samsung 840 evo ssd on my laptop. I did a totally crisp install of windows 8.1...and I'm having huge issues with windows problems and drivers. Windows update is, well, not updating.

I am using 2 x 840 EVO as cache drives in my unRAID box and this specific drive has some “issues” that might be good to know. The initial firmware did have some performance issues related to read performance so Samsung released a something they call Performance Restoration Software to fix it.

 

The other issue you can find with these drives is the write speed for large amount of data. This is due to the fact that the drive gets rather hot during write and there is an inbuilt throttling to prevent overheating. The result is that the transfer speed can drop to almost nothing until the drive cools down again.

 

Personally I would have chosen another drive, at least as cache drive, if I had understood the consequences of the throttling.

 

However I have difficulties understanding what I mentioned above could cause the problems you are having with your Laptop.

 

[BRiT]

Please, go read the SSD Torture Test series over at Techreport.com where they take average consumer grade SSD drives and put them through extreme tests. They survived far beyond their rated ranges. The longest going into the 2.5 PetaBytes written range.

 

Here is the final summary article:

 

http://techreport.com/review/27909/the-ssd-endurance-experiment-theyre-all-dead

 

[Spencer]

Here is my use case. I have 5 Macs connected by gigabit Ethernet to an unRAID server with sufficient capacity. If, each night,  I were to image a .dmg (disk image file) of a Mac hd ( 1 terabyte of data) to an unRaid server that had a 256 gigabyte SSD as cache, how would unRAID handle that? Would the cache be ignored and the write go straight to the storage array, incurring the parity write speed penalty?

 

[garycase]

If you're writing 1TB of data, you want to use a non-cached share [or get a MUCH larger cache drive  ]