Ubuntu – Slow Samsung 830 SSD!

performancesamsungssd

I did a fresh install of Xubuntu 12.04.1, ext4 with discard option & swappiness set to 0, mounting temp directory in RAM, (8GB.)

I found performance was not stellar, in fact, marginally better than traditional spinning storage media. This drive has had good reviews, yet I have seen Windows users complaining of slow performance online. It was anything other than zippy, with application loads being plain dog slow & not instant like I expected. I RMAd it eventually (GSmartControl would never complete long test.)

Slow performance on Windows = slow performance on Linux? Would I fare better with another brand?

I now have a 840 & it is not legendary, but faster than HDD.

Best Answer

Think you answered your own question there, the drivers used to control sata disks are normally pretty generic - unless you are using special hardware - and do the same on both Windows and Linux.

If this drive is slow on Windows it will probably also be slow on any Linux system. You should replace it or check if Samsung has a firmware upgrade that would eventually solve this issue.

Remember when I first changed from a spinning plate drive to a SSD, there is no comparison on boot and applications access. This is a disk model problem and should be handled with Samsung.

SATA II channel (3 Gbps) vs. SATA III channel (6 Gbps)

Looking at your timings it is similar to my /dev/sdc

$ sudo hdparm -tT /dev/sdc

/dev/sdc:
 Timing cached reads:   20494 MB in  2.00 seconds = 10255.92 MB/sec
 Timing buffered disk reads: 812 MB in  3.00 seconds = 270.63 MB/sec

What you are hoping for is timings like my /dev/sda

$ sudo hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   21598 MB in  2.00 seconds = 10809.23 MB/sec
 Timing buffered disk reads: 1566 MB in  3.00 seconds = 521.44 MB/sec

The explanation can be found using dmesg | grep SATA

$ dmesg | grep SATA
[    1.177247] ahci 0000:00:1f.2: AHCI 0001.0300 32 slots 6 ports 6 Gbps 0xf impl SATA mode
[    1.202732] ata1: SATA max UDMA/133 abar m2048@0xf1618000 port 0xf1618100 irq 27
[    1.202735] ata2: SATA max UDMA/133 abar m2048@0xf1618000 port 0xf1618180 irq 27
[    1.202736] ata3: SATA max UDMA/133 abar m2048@0xf1618000 port 0xf1618200 irq 27
[    1.202739] ata4: SATA max UDMA/133 abar m2048@0xf1618000 port 0xf1618280 irq 27
[    1.521294] ata1: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
[    1.521318] ata3: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[    1.521337] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[    1.521356] ata4: SATA link up 1.5 Gbps (SStatus 113 SControl 300)

Both /dev/sda and /dev/sdc are SATA III SSD's but sda is on a 6 Gbps bus (ata1) and sdc is on a 3 Gbps bus.

Comparison to SATA II 500GB HDD on a SATA III Channel

For comparison sakes here are the results of a 5400 rpm SATA II 500 GB HDD running on a SATA III (6 Gbps) channel:

$ sudo hdparm -tT /dev/sdb

/dev/sdb:
 Timing cached reads:   20632 MB in  2.00 seconds = 10325.32 MB/sec
 Timing buffered disk reads: 340 MB in  3.02 seconds = 112.76 MB/sec

Summary

This is a laptop and only has two SATA channels:

ata1 and ata2 are SATA III channels (6 Gbps)
ata3 and ata4 are SATA II channels (3 Gbps)

Linux/Ubuntu matches the device's SATA ability and channel's SATA ability to the lowest common denominator:

ata1 has a 240GB SSD SATA III attached.
ata2 has a 500GB HDD SATA II attached to SATA III channel.
ata3 has a 120GB PCIe half-height SSD SATA III attached to SATA II channel.
ata4 has a CD/DVD optical drive SATA I (1.5 Gbps) attached to SATA II channel.

Best Answer

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SATA II channel (3 Gbps) vs. SATA III channel (6 Gbps)

Comparison to SATA II 500GB HDD on a SATA III Channel

Summary

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