Different types of Server Drives?

[WrongLebowski]

Hello, I've got a Dell PowerEdge R710 I recently acquired and have been playing around with. I'm trying to add more drives to increase my storage. While I'm pretty sure I need SAS Drives, I'm still really confused about SAS vs SCSI vs SATA. Can anyone shed some light on this for me? Perhaps also educate me on what I need to be considering when buying SAS Drives second hand?

[NumLock21]

Lets get the old types out of the way. Ide and scsi. They're old and you're probably not going to see them unless the server is from 15+ years ago. 

New ones are sas and sata. Sata is the most basic. And sas is the newer version of the old scsi drive. Sas is based on scsi with improvements. Sas port can work with sata drives. But sata port will not work with sas drives.

[WrongLebowski]

So I could in theory throw some regular SATA drives into this SAS bay and make an array? Would the performance be that much worse? Is SAS just 10k+ RPM Drives?

[79wjd]

53 minutes ago, WrongLebowski said:

So I could in theory throw some regular SATA drives into this SAS bay and make an array? Would the performance be that much worse? Is SAS just 10k+ RPM Drives?

Yes, you can just throw sata drives into a sas backplane. As for performance, yes sas drives are faster, but it likely won't make any difference whatsoever unless of course you have like a dozen people hitting the server hard.

[Sevilla]

54 minutes ago, WrongLebowski said:

 

[Sevilla]

Sorry for the weird post above this one.

 

Keep in mind SAS drives are more expensive for similar performance to most standard mechanical drives. Also, unless you're buying enterprise grade drives, it'd be pointless if you're mostly looking for storage.

[tt2468]

1 hour ago, Sevilla said:

Sorry for the weird post above this one.

 

Keep in mind SAS drives are more expensive for similar performance to most standard mechanical drives. Also, unless you're buying enterprise grade drives, it'd be pointless if you're mostly looking for storage.

The improvements of sas over sata are quite large. Especially if someone gets sas ssds, as sas is already at 12Gbps. Sas hdds are generally faster rpm, which means faster random access speeds and response times. So while their constant read/write speed may not prove to be more than sata, the latency is what makes sas so popular.

[Sevilla]

1 minute ago, Kyle Manning said:

The improvements of sas over sata are quite large. Especially if someone gets sas ssds, as sas is already at 12Gbps. Sas hdds are generally faster rpm, which means faster random access speeds and response times. So while their constant read/write speed may not prove to be more than sata, the latency is what makes sas so popular.

You are correct, there are performance gains to using a 10k or 15k SAS drive, not going to deny that, but given that he sounds like he is just looking to throw in storage, why would anyone encourage a SAS drive? They're more expensive, transfer rates are not that much faster, and it doesn't really sound like he's looking to deploy a production server over an enterprise 10GbE network that requires low latency access.

I just use 4x4TB Seagate NAS drives in Raid Z. My transfer rates typically cap out at my gigabit network speeds between all wired machines.

[Wylly]

11 minutes ago, Sevilla said:

You are correct, there are performance gains to using a 10k or 15k SAS drive, not going to deny that, but given that he sounds like he is just looking to throw in storage, why would anyone encourage a SAS drive? They're more expensive, transfer rates are not that much faster, and it doesn't really sound like he's looking to deploy a production server over an enterprise 10GbE network that requires low latency access.

I just use 4x4TB Seagate NAS drives in Raid Z. My transfer rates typically cap out at my gigabit network speeds between all wired machines.

I agree. The difference in price is not worthy for a domestic use.

[NumLock21]

them 2.5" nvme drives have a similar interface to a SAS drive. The U.2 is similar to a mini-SAS port

[scottyseng]

6 hours ago, WrongLebowski said:

So I could in theory throw some regular SATA drives into this SAS bay and make an array? Would the performance be that much worse? Is SAS just 10k+ RPM Drives?

Yes, you can put SATA drives in a SAS backplane. I have six 4TB WD Reds in mine along with two SAS 4TB WD Re drives. The performance will not be worse. My Red drive gets roughly 160MB/s sequential read / write while the WD Re gets 180 MB/s read and write. The 4TB Red costs $140...while the Re SAS costs $250.

 

The main bottleneck (With a lot of drives) would be the SAS RAID or HBA card connecting the backplane.

[dalekphalm]

Another thing to note is that SAS HDD's are not intrinsically faster. While typically, we'd hear about 10k and 15k RPM SAS HDD's, many are also 7200 RPM. A 7200 RPM SAS drive vs a 7200 RPM SATA drive are not terribly different, performance wise.

 

@scottyseng are you using 5400 RPM Reds, or 7200 RPM Red Pro's? Either way, not a very large difference compared to the SAS Re drives.

[scottyseng]

6 minutes ago, dalekphalm said:

-snip-

Yeah, I agree SAS hard drives aren't faster. They just can do more (have more error codes than SATA, full bandwidth in both directions, and generally are for server use (lower uncorrectable reads count)).

 

The 5400RPM Reds. Yeah, it surprised me how fast those Reds were compared to the Re drives. I'm switching over to Re Drives because I need a lot of them in one chassis for my NAS (The Reds aren't safe in a server chassis beyond 8 drives, and 16 for the Red Pro (I need to fill up 24 bays)...and I figured I might as well go more overkill and the SAS version). This is on my LSI MegaRAID 9260 8i raid card with a SAS 6Gb/s supermicro backplane.

[leadeater]

Just take note if you are using hardware RAID you can not put SAS drives and SATA drives in the same array. This is not an issue if using anything software based i.e. ZFS.

 

As @dalekphalm mentioned there are different types of drives:

NL-SAS: 7200 RPM, SAS controller, dual path

SAS: 10000 or 15000 RPM, SAS controller, dual path

SATA: 5400 or 7200 RPM, SATA controller, single path

 

As far as sequential performance goes all of these are fairly close for long term sustained transfer. Yes the higher RPM and SAS ones will be slightly faster but really not that much compared to SSD. The real difference is in random I/O and multi user access. SAS disks handle higher queue depths, typically have larger caches and have much better seek times (due to RPM).

 

For home use you are unlikely to push your storage hard enough to get the benefits from SAS.