How RAID can give your hard drives SSD-like performance

irBosOtter said:
Not sure why it will be on 6Gb SATA port, or are you only referring to cheaper SSD's for home use where your pc will have 6Gb SATA ports? Our EMC SAN (Netapp flash SAN as well) has 12Gb backplane, and 47 1.6Tb SSD's has 12Gb SAS, then again these enterprise SSD's costs R30 000 each so does get a bit expensive
There are many SSD's with 12Gb SAS ports and raid cards with 12Gb capabilities where they will be plugged into, but suppose they are not for home use

We have 9 SAN's, ranging from entry level consisting of 80 1Tb NLSAS 7200 disks in RAID 10 to all flash RAID 5 arrays costing millions, all FC from 8Gb to 16Gb, Read and write speeds are a given on all of them, not much difference at all, but the SAN's with only 7200rpm disks are not even good enough for backups anymore so replacing them with 10K SAS disks to speed things up, although I would go SSD for that as well as the backups are IO intensive and even the 10K disks will be the bottleneck.

Oh and the testing we ran on one SSD is a 900Gb internal SSD in a Dell server, also 12Gb SAS, then again, enterprise equipment that no home user will buy
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Because SSD's are still by and large SATA-3 interfaced - and this isn't just about the bus its the SATA-3 specification, to quote from another source:

Difference between SATA I, SATA II and SATA III
What is the difference between SATA I, SATA II and SATA III?
SATA I (revision 1.x) interface, formally known as SATA 1.5Gb/s, is the first generation SATA interface running at 1.5 Gb/s. The bandwidth throughput, which is supported by the interface, is up to 150MB/s.

SATA II (revision 2.x) interface, formally known as SATA 3Gb/s, is a second generation SATA interface running at 3.0 Gb/s. The bandwidth throughput, which is supported by the interface, is up to 300MB/s.

SATA III (revision 3.x) interface, formally known as SATA 6Gb/s, is a third generation SATA interface running at 6.0Gb/s. The bandwidth throughput, which is supported by the interface, is up to 600MB/s. This interface is backwards compatible with SATA 3 Gb/s interface.
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That means if you want to cross the 6gig limit - you have to use a controller that multiplexing across multiple disks (a 12gig RAID controller) or go m.2 - which doesn't have the 6gig limit.
 
irBosOtter said:
For a setup at home that is quite impressive!
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A disclaimer - I do most of my work from my house - so this isn't just some casual gaming setup - its an investment that lets me work more efficiently. I will admit, a lot of this hardware is simply not cost viable for a lot of people because of the cost (those raid controllers are pricey, and those hard drives are going to run you a whack of cash as well, but they are still cheaper than the SSD options!)

If I had the money though - I'd use the same Avago controller and backend it with 8 x PM1633a drives (15 terabyte SSD's made by Samsung) but at $10k USD a disk - I'd need to win the lottery first!
 
AndrewAlston said:
Because SSD's are still by and large SATA-3 interfaced - and this isn't just about the bus its the SATA-3 specification, to quote from another source:



That means if you want to cross the 6gig limit - you have to use a controller that multiplexing across multiple disks (a 12gig RAID controller) or go m.2 - which doesn't have the 6gig limit.
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Jip we only use 7200 drives with 12Gb SAS interfaces in one SAN, rest all 10K rpm (Oldest SAN still has 6Gb SAS drives though) SATA has no place here by us in the server rooms
 
AndrewAlston said:
A disclaimer - I do most of my work from my house - so this isn't just some casual gaming setup - its an investment that lets me work more efficiently. I will admit, a lot of this hardware is simply not cost viable for a lot of people because of the cost (those raid controllers are pricey, and those hard drives are going to run you a whack of cash as well, but they are still cheaper than the SSD options!)

If I had the money though - I'd use the same Avago controller and backend it with 8 x PM1633a drives (15 terabyte SSD's made by Samsung) but at $10k USD a disk - I'd need to win the lottery first!
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Dear lord, you need to win the lottery a few times for that haha!
 
irBosOtter said:
Jip we only use 7200 drives with 12Gb SAS interfaces in one SAN, rest all 10K rpm (Oldest SAN still has 6Gb SAS drives though) SATA has no place here by us in the server rooms
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By the way - does anyone on this forum happen to know a supplier in South Africa for Hitachi drives (HGST).

Up until now I've been buying mine off amazon and importing myself. I see they have a very pretty 12 terabyte 7200RPM Helium filled SAS disk out now - which on amazon is selling for a pretty reasonable $440 USD. Btw - I can say - I have run HGST drives for 5 years now - under some pretty heavy load - and I have yet to have a drive fail on me - they make an awesome product!
 
yeah no. not even close.

well, maybe top of the range hdd raid vs bottom of the range ssd
 
access said:
yeah no. not even close.

well, maybe top of the range hdd raid vs bottom of the range ssd
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Bottom of the range ssd vs top of the range ssd makes no difference - they are both SATA-3 which is 6gigabit a second - and a 12gigabit a second raid controller is going to outrun that - period
 
AndrewAlston said:
But seriously - throw a 12gigabit controller in there - and 8 7200 rpm disks - and in sustained transfers you're gonna very quickly outrun SSD's (which btw are normally on 6gigabit bus) - but the cost point of doing this properly - means you either do it with an insane amount of disk space - or it will push your cost per gig through the roof.
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But it's apples with pears. RAID + SSDs to the same cost of that above RAID setup... what will that do for you?
 
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AndrewAlston said:
By the way - does anyone on this forum happen to know a supplier in South Africa for Hitachi drives (HGST).

Up until now I've been buying mine off amazon and importing myself. I see they have a very pretty 12 terabyte 7200RPM Helium filled SAS disk out now - which on amazon is selling for a pretty reasonable $440 USD. Btw - I can say - I have run HGST drives for 5 years now - under some pretty heavy load - and I have yet to have a drive fail on me - they make an awesome product!
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https://www.senetic.co.za/hgst/hgst...MWrPS1mdbzQHpk5gIDQEis84eBTS3ZzhoCBYsQAvD_BwE

I see they have them on their site, no idea who that company is though
 
AndrewAlston said:
Bottom of the range ssd vs top of the range ssd makes no difference - they are both SATA-3 which is 6gigabit a second - and a 12gigabit a second raid controller is going to outrun that - period
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Two Samsung 850 EVO 500GB drives in RAID 0 will outrun your array for a fraction of the price - and that's on SATA 3 via Intel or AMD's chipsets.

irBosOtter said:
https://www.senetic.co.za/hgst/hgst...MWrPS1mdbzQHpk5gIDQEis84eBTS3ZzhoCBYsQAvD_BwE

I see they have them on their site, no idea who that company is though
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International brand, founded in London. They've been around since 2009 They have an e-Commerce product that they license to franchisees globally, which basically works like Esquire's reseller service.
 
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AndrewAlston said:
Bottom of the range ssd vs top of the range ssd makes no difference - they are both SATA-3 which is 6gigabit a second - and a 12gigabit a second raid controller is going to outrun that - period
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lol what? since when is bottom of the range adata ssd equal to a top of the range samsung ssd? share that **** youre smoking.

since you are throwing in a 12gbps controller, why not throw in a pcie ssd or some nonsense.

wtf kind of comparisons are you making hahaha

fact is ssd is faster - periods


edit: on top of that the controller speeds differ too, like marvell vs intel. some people raid their ssd but their controller cannot go faster than if it was a single drive anyway
 
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AndrewAlston said:
Figured this would be of interest..

These are tests I just ran on one of my machines -

First test - the Samsung 512gig m.2 nvme drive:

View attachment 515535

Note - its a very consistent result - and the random access speeds are *extremely* fast - again though - thats not limited by 6gig SATA speeds.

Second result - this was done against a 8 x 6TB HGST based raid on an Avago 9361-16i Raid controller running RAID-6

View attachment 515539

Random access times are way way up here - but on the sequential read - I'm still outrunning any standard SSD because I'm sitting at 7.4gigabit average there - higher than the port speed available to an SSD (and actually bursting higher than the m.2 drive)

Third result - this was done against another array on the same controller - this time on 8 x 10TB HGST 7200 RPM drives - these drives are newer and have MUCH more built in cache on the drives

View attachment 515541

You'll notice the random access speeds are slightly better than the second test - at 7.7ms - but the average speed is pretty consistent with the previous test.
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Do us a fav. Cut out the sequential read tests. That's useless info mostly. Please post 4K random read / write tests - this is how drives behave in an OS... unless you're using them for once off storage as in a backup device that is archived...
 
The only time this is true...is if you are RAIDing SSD's.

Otherwise it's all bull**** in real world usage.
 
CataclysmZA said:
Two Samsung 850 EVO 500GB drives in RAID 0 will outrun your array for a fraction of the price - and that's on SATA 3 via Intel or AMD's chipsets.



International brand, founded in London. They've been around since 2009 They have an e-Commerce product that they license to franchisees globally, which basically works like Esquire's reseller service.
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Actually - thats not accurate - for two reasons.

Firstly - the performance is pretty similar (tomorrow I'll paste you a test, I've got anotehr machine with those as boot drives, they peak at pretty much the same point and sustained is also reasonably similar)

Secondly - on the price point - as I stated earlier - raid makes sense on large disks - if you had to try and put enough samsung EVO's in place to replicate the speed - it would cost you one hell of a lot more. Your price per gig on SSD is massive - a 4TB SSD will still cost you R20k+ - a 10TB disk can be had for R6k odd - raid 8 x 10, you're in around 50 grand at end up with similar performance with 60 odd TB active after raid loss - take 8 x 4 SSD's you get 32 TB, and have spent 160 grand - and if you don't raid them you don't have the redundancy either - if you do - you're down to 24TB of space - or R6.6k per TB - vs probably a R1k per TB on the 12gig raid - so on large capacity systems - the raid is cheaper - WAY cheaper - for the same performance.
 
AndrewAlston said:
Firstly - the performance is pretty similar (tomorrow I'll paste you a test, I've got anotehr machine with those as boot drives, they peak at pretty much the same point and sustained is also reasonably similar)
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I know they'll be similar, but the two SSDs in RAID will edge out a win compared to your RAID array. Sustained speeds will be more consistent, but your latencies will be far lower. Sure, you can burst higher than what a 950 Pro can manage, but that's a pointless statistic considering you can't maintain that speed for very long.

AndrewAlston said:
Secondly - on the price point - as I stated earlier - raid makes sense on large disks - if you had to try and put enough samsung EVO's in place to replicate the speed - it would cost you one hell of a lot more.
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I'm assuming that you meant size here, and not speed. On size, we are in agreement - there's no way you're building a 32TB HDD array and a 32TB SSD array for the same price. Especially when you're dealing with stuff that gets an "enterprise" label slapped on it along with the firmware to go with it. But you're never going to get anything close to the same performance out of them. Hook up eight SATA SSDs to that MR9361 and watch it bottleneck because there aren't enough PCIe lanes for all the bandwidth you have on tap.

Dividing the average read speed in your best result - 981.6MB/s - gives you a per-drive average of 122.7MB/s, and a top burst speed of 183.2MB/s. It's decent, but there are drives available today using helium that I recall approaching 200MB/s pretty consistently. WD's new DC HC530 is rated for 267MB/s using PMR with helium, but that's only at the start of the disk's readable sectors, slowing down as the head moves further out the platter.
 
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