03
Jun
2016

2016 NAS: Seagate 4TB NAS Drives

So, now onto the most important part of this build. The hard disks. I had a conundrum: do I get the WD 4TB Red drives or do I go for the Seagate NAS drives?

I scoured Reviews-land, searching far and wide for a justifiable reason to go for the WD Reds over the Seagate NAS drives. The price difference was about £30 per drive, so with three drives that is a fair bit of margin. My past experience also pointed to Seagate drives for RAID – the one WD drive I’ve had has corrupted photos in the past. I will be using BTRFS – so I won’t have to worry so much about bit-rot.

Aaaaaaaaaaand the Seagate drives went on sale. So – here we are:

My, are these drives absolute beasts. They’re the heaviest hard disks I’ve ever had. And I’ve had a lot of hard disks.

Time for some performance numbers, eh? Let’s do some classic hdparm –tT /dev/sdx commands and see what we get:

hdparm -tT /dev/sd[abcd]

/dev/sda:
Timing cached reads: 14610 MB in 2.00 seconds = 7311.68 MB/sec
Timing buffered disk reads: 472 MB in 3.00 seconds = 157.30 MB/sec

/dev/sdb:
Timing cached reads: 14408 MB in 2.00 seconds = 7210.30 MB/sec
Timing buffered disk reads: 488 MB in 3.00 seconds = 162.54 MB/sec

/dev/sdc:
Timing cached reads: 19482 MB in 2.00 seconds = 9753.21 MB/sec
Timing buffered disk reads: 498 MB in 3.01 seconds = 165.59 MB/sec

/dev/sdd:
Timing cached reads: 15366 MB in 2.00 seconds = 7690.23 MB/sec
Timing buffered disk reads: 654 MB in 3.00 seconds = 217.95 MB/sec

So, sda, sdb and sdc are the three hard disks. sdd is the boot SSD (plugged into a SATA-2 port). We are hitting about ~160 MB/s on the hard disks. Also, the fastest hard drives in terms of sequential read speeds I’ve ever had.

These Seagate drives run at 5900 RPM, which is slower than the standard 7200 RPM you see on most consumer drives, and way less than the 10k or 15k RPM you see on server drives. The lower spindle speed mainly impacts access time, since the drive has to wait longer for the data to reach the read head. To test for access time, I like to use seeker.

Here are the results:

./seeker /dev/sda

Results: 79 seeks/second, 12.64 ms random access time

./seeker /dev/sdb

Results: 76 seeks/second, 13.01 ms random access time

./seeker /dev/sdc

Results: 78 seeks/second, 12.72 ms random access time

./seeker/dev/sdd

Results: 5520 seeks/second, 0.18 ms random access time

So that’s an average of ~78 seeks/second, or 12.79 ms of random access time. In comparison, the SSD is obviously laughing, and my consumer Seagate 500GB HDD’s get 64 seeks/second (15.6 ms). So these slower RPM NAS drives are doing better in terms of access time than the 7200 RPM consumer drives. Nice.

Okay, I know what you are saying. What about real-world performance? How fast is BTRFS RAID-5? Well, I can dd a file and get 250MB/s plus. That’s plenty for gigabit ethernet. What about random access? Well, I can test that using sysbench! I detail the settings I’ve used in this post. The results are below:

3x 4TB Seagate NAS BTRFS RAID-5: 394.62Kb/sec

3x 500GB Seagate Barracuda 7200.12 mdadm RAID-5: 762.55Kb/sec

NAS SSD Kingston SSDNow 300 120GB: 34.728Mb/sec

So yeah, the NAS drives in real world cases with BTRFS are not as fast as a mdadm array. I believe the checksumming that BTRFS could be playing a part in the access time. I would like to note that this is not representative of what I will be asking of the NAS – it will mainly service Plex movies (large files). It has more than enough performance for that task! If I need a fast space in the NAS, I have the SSD there anyways!

In terms of acoustics, the drives are fairly quiet. Not silent, but you can’t really hear them seeking very much. It is quite cool hearing them spin up, since they take a fair bit of time to reach full speed. In terms of temperatures, they don’t get warm at all. 32-33 degC is the highest I’ve seen from the middle drive in the stack, and they don’t seem to fluctuate that much.

All in all, these are awesome drives for the money and space that you get. I have 8TB of usable storage space that I know will take me a good while to fill! Tomorrow’s post will talk more about power consumption of the drives, so stay tuned for that! Ta-Ta for now!

2016 NAS: The Logic Case SC-N400 (Norco ITX S4)
2016 NAS: Power Consumption

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