SATA SSD vs SAS HDD - Which is faster?

[Jonathan4]

Hi everybody, 

We have a Hyper-V server on site that has 3 x 1.2TB SAS HDD hard drives in a RAID 5. 

The software company has recommended that we "move our server VM on to SSD so that it will run faster". So I have identified SSD hard drives that are 240GB, which will be enough to host their server VM. 

My difficulty is that the SSD options are on the SATA interface and the drive transfer rate is half of the existing SAS HDD hard drives. 

Is there any point in me moving the server VM to these disks, will there be any performance advantage or am I making a big mistake?

[KevinSpringPM]

SATA SSDs are far far faster in general. Just because a sas hard drive has a 12gb link speed doesn't mean it's faster. The drive transfer rate in your image is just the hypothetical limit, not the actual transfer speed.

SATA SSDs are like a car driving 45-55 when the speed limit is 55

SAS HDDs are like a car driving 20 when the speed limit is 100

The sata SSD is still faster even though it's theoretical speed limit is lower. How that will benefit your specific application I can't really speculate on, but it can only help.

[SanjeevGoyal]

Hello,

I hope all is well.

HDDs usually have more storage space, but SSDs are faster.

Both SSD SAS drives and SSD SATA drives are faster than their HDD counterparts.

They have the same characteristics though: SATA is still faster writing data, while SAS is faster at reading and writing data continuously.

 Please follow the below link for more clarification.

 https://store.hp.com/us/en/tech-takes/sas-vs-sata#:~:text=HDDs%20usually%20have%20more%20storage%20space%2C%20but%20SSDs%20are%20faster.&text=Both%20SSD%20SAS%20drives%20and,reading%20and%20writing%20data%20continuously.

 SSD performance for SAS and SATA

There are 2 main types of hard drives:

• Hard disk drive (HDD)
• Solid-state drive (SSD)

A hard disk drive looks a little bit like a record player. There’s an actuator arm that uses electromagnetism to write data onto a rotating platter. A solid-state drive has no moving parts and uses small chips to store data instead.

Which one is better? HDDs usually have more storage space, but SSDs are faster. An HDD must wait for the platter to rotate to the correct location before it reads or writes data. An SSD doesn’t have any moving parts that it needs to align, so its read/write speeds are uniformly faster [10].

Both SSD SAS drives and SSD SATA drives are faster than their HDD counterparts. They have the same characteristics though: SATA is still faster writing data, while SAS is faster at reading and writing data continuously.

SSD performance for SAS and SATA There are 2 main types of hard drives:

• Hard disk drive (HDD)
• Solid-state drive (SSD)

A hard disk drive looks a little bit like a record player. There’s an actuator arm that uses electromagnetism to write data onto a rotating platter. A solid-state drive has no moving parts and uses small chips to store data instead.

Which one is better? HDDs usually have more storage space, but SSDs are faster. An HDD must wait for the platter to rotate to the correct location before it reads or writes data. An SSD doesn’t have any moving parts that it needs to align, so its read/write speeds are uniformly faster [10].

Both SSD SAS drives and SSD SATA drives are faster than their HDD counterparts. They have the same characteristics though: SATA is still faster writing data, while SAS is faster at reading and writing data continuously.

 If you feel this was helpful please click the KUDOS! thumb below!   

Regards,

[Jonathan4]

Hi there, 

Thank you for your posts. I think the first post gives me enough information to go back to the client with. 

It would be better if this information was very clearly available on the spec sheets for the drives. I'm not sure if that's possible in this case, but thanks for you help with this. 

regards, 

[KevinSpringPM]

Hi Johnathan,

This info is mostly available today in our quickspecs, where we list the read/write performance of each current SSD and HDD for you to compare. The specific drives you're looking for may be end of life so they aren't on the quickspecs anymore unfortunately, but you can find similar SSDs and HDDs to compare and see that the SATA SSDs have much higher performance across the board than the SAS HDDs do.

SSDs

HDDs

[JackWalsh]

In simple terms, SAS & SATA are two technologies that enables transfer of data from motherboard to hard drives and vice versa. As far as usability is concerned SAS hard drives are usually preferred where higher data transfer rates are high, mostly in data centers and enterprise networks. Installing SAS HDD in a workstation and Servers helps in achieving higher performance while ensuring that the data transfer rates are optimal. Since servers can utilize multiple hard drives, there is no issue with the storage capacities & limitations of a singe sas hard drive. Comparatively SAS hard drives have lower data storage capacities but the tech enables its data transfer performance much higher than those in SATA. SATA hard drives are mainly a preferred option for desktop pcs, due to their high storage capacities. When it comes to SSDs & HDDs the SSDs (Solid State Drives) are much better & faster than HDDs (hard disk drives)

[KevinSpringPM]

Your reply is plagiarized from a 2011 blog post... Why? Not productive.

Source: https://www.turbotekcomputer.com/resources/small-business-it-blog/bid/57900/sata-vs-sas-what-is-the-difference

[krzysztoflaskow]

sata ssd

[kira12]

Hi all,

HDD is limited with the spinning Disks Transferrate. SSD Cells are faster als the Interface Transferrate. SATA is limited by 6Gb/s, SAS is limited by 12Gb/s (if the Disk and Controller can handle the Speed) So you can see what Drive is faster.

best regards ré

P.S. i can show you Speedresults from 3,5"-HDDs, 6G-SATA and 12G-SAS Disks....

[Interlink_Admin]

Kira12,

What were the results of your speed tests? Based on what you said I got the impression you were saying the SATA SSD would be faster than the SAS HDD. Logically, I thought the same thing, but I happened to find myself in this situation and my speed tests revealed the opposite. Disclaimer - I am not the most knowledgable on this so I may be missing something obvious to explain my results.

I'm running an HP ProLiant ML350 Gen 9 server with a Smart Array P440ar controller. I have Windows Server 2016 booting to HP EG000300JWBHR 300 GB 10k RPM 12 Gbps SAS mechanical hard drives in RAID-1. One of these failed which prompted me to go down this path and test SAS mechanical hard drive versus SATA SSD. I had 2 spare Crucial MX300 SSD's which I thought would perform better than the SAS mechanical hard drives. My idea was to put the 2 Crucial MX300's into a RAID-1 logical drive and clone the boot drive to that. To test speed I put one of the Crucial SSDs into the ML350 server and created a RAID-0 logical drive to compare. Much to my surprise, the SAS mechanical drive blew away the SATA SSD. The results of my tests linked below.

SAS default profile results 
SAS real world profile results 
SSD default profile results 
SSD real world profile results 

I would appreciate anyone's insight or comments as to my results whether their experience has been the same or if I've done something incredibly stupid that would affect the results. Tests were run using Crystal DiskMark CrystalDiskMark – Crystal Dew World (crystalmark.info)

[KevinSpringPM]

I'm unable to open your results files but 9 times out of 10 when someone gets this sort of result, it's because the speed test actually hit the DRAM of the controller cache, not the hard drives. For SSDs, many operations skip the cache, so that's how you can get a hard drive appearing to be faster than an SSD, when of course it is not.

[Interlink_Admin]

So you're saying that the SATA SSD should be faster than the SAS HDD?

My apologies for the bad links on my results, these should work:

SAS default profile 
SSD default profile 
SAS real world profile 
SSD real world profile 

[Moderator edit: The above links are no longer valid.]

[KevinSpringPM]

Yes, set the test size to something greater than 4 Gib instead of 1 GiB and see how that affects the test results.

[KevinSpringPM]

Alternatively, go into the HPE SSA tool and disable the controller cache and then retest. That way you can test the actual drive speeds rather than what you're getting now which is the speed of the cache device. Which is awesome, that's what the cache is supposed to do and it can be really helpful. We just don't want to mistake that for saying that a SAS hard drive is faster than an SSD

[Interlink_Admin]

Thank you for the insight Kevin, it's much appreciated.

[Interlink_Admin]

Hi Kevin,

I wanted to thank you again for your help on this. After running the tests on larger files and doing a separate test where I disabled the controller cache I was able to get the results I expected and see the SSD performed far better than the SAS HDD which was logically what I knew it should be. As a bonus I was able to find my (previously missing) installation media and license key so I reinstalled Windows instead of having to hassle with trying to clone the drives. With the SAS HDD it took Windows Server 2016 35 seconds to boot up and with the SSD it took Windows Server 2016 13 seconds to boot up.

Your help is much appreciated.

[krisd443]

For a smaller array I would sitck to SSD. If you expect to need more space and have a Gen10 Proliant server with a current gen RAID card, you'd also have the option to run SmartCache which to some degree gives you the best of both worlds. SmartCache comes free with some controllers but we've been buying licenses for other machines in new builds because we see huge speed increases from its implementation.