Caching Needs and SSDs
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But hey, now I know! I suppose with xByte, no need to choose a H330 if you can get the best there is for only $200 more.
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Benefits of being part of these communities... always learning new things!
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@Tim_G said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
@Tim_G whole thing is warrantied through xByte too.
I don't know... I guess if xByte sells everything Dell sells, but for half the price, there's no reason to buy through Dell as far as I can tell, as long as you are getting the same warranties and support that Dell offers. Perhaps Dell should just shut down their online store and redirect to xByte IMHO.
They are both a normal dell reseller and a refurb dell shop. The refurb have warranties and are "new" but like open box that can't legally be called new. But not used.
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@scottalanmiller said in Caching Needs and SSDs:
@Tim_G said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
@Tim_G whole thing is warrantied through xByte too.
I don't know... I guess if xByte sells everything Dell sells, but for half the price, there's no reason to buy through Dell as far as I can tell, as long as you are getting the same warranties and support that Dell offers. Perhaps Dell should just shut down their online store and redirect to xByte IMHO.
They are both a normal dell reseller and a refurb dell shop. The refurb have warranties and are "new" but like open box that can't legally be called new. But not used.
A server I recently built is now 10k cheaper on xByte. (well 1.5 years ago) I guess a combination of time + xByte being cheaper.
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@Tim_G said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
@Dashrender said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
Just looked on xByte, the price delta is $230. And that's for the big 2GB cache model.
Considering the cost of the storage, $230 is nothing, and totally worth the cost for the benefit.
That's my thought. It's a rare use case where the speed and protection that this adds, along with blind swap and upward system compatibility with all enterprise platforms, is a pretty big deal. Plus it offloads work from the main CPUs, which is minor.
I was going by buying it new on a new Dell server through Dell so the whole thing is covered by their warranty. According to just the regular site, it's over $400 more than the H330. I normally wouldn't buy a new server from Dell, and then get the RAID Controller through a 3rd party.
Even at $400, that's the cost of one drive - for all the things you get, I'd easily do it! i used to drop $800+ on RAID controllers, to drop $400 would make me happy!
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@Tim_G said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
@Tim_G said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
@Tim_G whole thing is warrantied through xByte too.
I don't know... I guess if xByte sells everything Dell sells, but for half the price, there's no reason to buy through Dell as far as I can tell, as long as you are getting the same warranties and support that Dell offers. Perhaps Dell should just shut down their online store and redirect to xByte IMHO.
They are both a normal dell reseller and a refurb dell shop. The refurb have warranties and are "new" but like open box that can't legally be called new. But not used.
A server I recently built is now 10k cheaper on xByte. (well 1.5 years ago) I guess a combination of time + xByte being cheaper.
Time might be a big factor
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@Tim_G said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
@Tim_G said in Caching Needs and SSDs:
Double caching seems dangerous or at least slow things down a little.
Not dangerous or slow. We do similar things for high speed websites. But in the opposite direction, of course.
Double caching is no more dangerous than single caching, if caching is dangerous, it's dangerous. If it is safe, it doesn't matter how many times you do it.
As for latency, it's not an issue and all hardware RAID systems like this do it under the hood because it's the only good way to add the SSD layer. You always want a RAM cache on the front end, and you need disks on the back end. The question is, do you want SSD in the middle or not.
If you think about the performance leap from spinners to SSD, it makes total sense to have SSD in front of them for cache. Even a little SSD helps the spinners a LOT. Same difference from SSD to RAM. RAM is orders of magnitude faster than SSD, just like SSD is over spinners. So the gains are similar. And RAM doesn't wear like SSD does, so it doesn't just speed things up but allows for fewer and more efficient writes and that means longer SSD life which actually adds reliability.
Also, cache allows writes to happen faster allowing more data to be protected before a failure.
I have a main Hypervisor running with a PERC H730p (2gb cache), configured with write-back (uses the 2gb cache) for all volumes, even the SSD SanDisk DAS Cache slow HDD volume.
But if someone has a H330 (without a cache), you can still use an SSD cache (such as with SanDisk DAS Cache) perfectly fine. You don't NEED to have the onboard RAID card cache. You can even write-through to your SSD cache volume.
Don't use DAS Cache. Western Digital had basically discontinued the product. If you rely on in within your infrastructure it means you have something on I/O path going wrong ;(
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@Tim_G said in Caching Needs and SSDs:
@JaredBusch said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
@JaredBusch said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
Also, the need for the battery went away long ago. That's a 2000's problem.
Do what? This was a standard feature as recently as 2012 on the Dell T600 line.
Standard as a cheaper downgrade, right?
Standard as in it was the "Dell Recommended" option at the time.
And it looks like it was 2011.
And it looks like the R720xd I purchased from XByte to replace that server has the PERC H710P with a battery.
This page here says it uses NVCache. Why does it have a battery?
NV = battery-powered DRAM + flash for persistent storage. On power outage detected battery will drive on-board micro controller go gain access to memory bus and copy fast but volatile DRAM to slow but NV flash.
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@scottalanmiller said in Caching Needs and SSDs:
One of the biggest benefits to Starwind is that it uses RAM cache in its SAN stack to give you millions of IOPS, instead of tens of thousands of IOPS, for lots of operations.
Yes we do! Will be happy to help to anybody who wants to play with it. Here:
https://www.starwindsoftware.com/starwind-virtual-san-free
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@Tim_G said in Caching Needs and SSDs:
I WISH there was a built-in way in Windows Server to use RAM as cache. I think it's awesome that StarWind has it.
Well it opens a big can of worms if done in the wrong way. People don't understand block DRAM cache is dangerous w/out synchronous replication between nodes to keep multiple copies of the cache coherent between independent "controller" nodes and sort of a log at the back end, they install StarWind on a single controller w/out UPS, experience power outage and few GBs of transactions lost and... come blame us!
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@KOOLER said in Caching Needs and SSDs:
@Tim_G said in Caching Needs and SSDs:
@scottalanmiller said in Caching Needs and SSDs:
@Tim_G said in Caching Needs and SSDs:
Double caching seems dangerous or at least slow things down a little.
Not dangerous or slow. We do similar things for high speed websites. But in the opposite direction, of course.
Double caching is no more dangerous than single caching, if caching is dangerous, it's dangerous. If it is safe, it doesn't matter how many times you do it.
As for latency, it's not an issue and all hardware RAID systems like this do it under the hood because it's the only good way to add the SSD layer. You always want a RAM cache on the front end, and you need disks on the back end. The question is, do you want SSD in the middle or not.
If you think about the performance leap from spinners to SSD, it makes total sense to have SSD in front of them for cache. Even a little SSD helps the spinners a LOT. Same difference from SSD to RAM. RAM is orders of magnitude faster than SSD, just like SSD is over spinners. So the gains are similar. And RAM doesn't wear like SSD does, so it doesn't just speed things up but allows for fewer and more efficient writes and that means longer SSD life which actually adds reliability.
Also, cache allows writes to happen faster allowing more data to be protected before a failure.
I have a main Hypervisor running with a PERC H730p (2gb cache), configured with write-back (uses the 2gb cache) for all volumes, even the SSD SanDisk DAS Cache slow HDD volume.
But if someone has a H330 (without a cache), you can still use an SSD cache (such as with SanDisk DAS Cache) perfectly fine. You don't NEED to have the onboard RAID card cache. You can even write-through to your SSD cache volume.
Don't use DAS Cache. Western Digital had basically discontinued the product. If you rely on in within your infrastructure it means you have something on I/O path going wrong ;(
I haven't experienced any issues with SanDisk DAS Cache, nor any performance degradations... only huge performance increases and good experiences.
So you'll have to explain why it's bad if the only thing it's done for me is positive boosts in every aspect that I can monitor.
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@Tim_G said in Caching Needs and SSDs:
you have something on I/O path going wrong ;(
What do you mean? Everything looks good and appears to be going smooth according to all monitoring. No errors or performance issues.
It's been doing a very good job the past couple years. I keep it fairly updated. So if something recent broke something on it, let me know and I'll hold off on updating.
