Poor SSD performance

[allistarM]

Hi there,
I recently purchased a SanDisk ExtremePro 240Gb. The computer it's going in is an ASUS P5B deluxe. The drive is plugged into a 6Gb/s SATA card (a Rocket 620A Dual Port PCI-Express adapter). This adapter is plugged into a PCI-ex4 slot. The BIOS is using AHCI mode for SATA disks. I run kernel 4.4.6-gentoo.

I have formatted the SSD into two Ext4 partitions (one 64Mb and the other is the remaining). Hdparm reveals this:

[eccerr0r]

Is your controller the Highpoint Rocket 620A? This looks like a x1 PCIe card, or is it really x4?

With a x1, 190MB/sec might be a little low (theoretical should be in the mid 200s) but not completely unexpected. Then the onboard SATA2 connectors may not be so bad compared to a x1 PCIe.
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Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?

[allistarM]

Yes, it's a Highpoint Rocket 620A. It reports at x1 when it boots. x1 is reportedly 250 MB/s. SATA3 is 600MB/s.

I've added a grub entry for the root partition to be on the SSD. Booting is faster but not amazingly so.

I'll try plugging the drive into one of the spare onboard SATA2 headers but I can't see how that would make it any faster. Since I've plugged the SATA adapter into the longer PCIe-x4 slot it appears I may benefit from a higher specced card (i.e. PCIe-x4).

My SSD reports this in hdparm:

Timing cached reads: 7030 MB in 2.00 seconds = 3517.88 MB/sec
Timing buffered disk reads: 566 MB in 3.01 seconds = 188.16 MB/sec

My spinning SATA disk reports this:

Timing cached reads: 7004 MB in 2.00 seconds = 3504.22 MB/sec
Timing buffered disk reads: 230 MB in 3.02 seconds = 76.12 MB/sec

Am I right that it's the bottom number that's important here?

[frostschutz]

76MB/s is a tad slow.

You should benchmark access times though, they are more important than linear throughput. SSD is all about access times and IOPS...

SSD should be fine onboard even if it's "only" SATA2.

[pilla]

The so called "cached reads" means that you are reading it most likely from your RAM instead from the disk most of the time. Hence, it is not very interesting if you want to get a measure of your disk's performance.
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"I'm just very selective about the reality I choose to accept." -- Calvin

[eccerr0r]

SATA2 is 3Gb/sec and if it tops out a 300MB/sec it's still a win over PCIe x1 at 250MB/sec.

I still have SATA2 spinner disks that only do 70-80MB/sec but yes newer ones should exceed 100MB/sec on sequential reads.
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?

[allistarM]

My motherboard is fairly old, but has lasted me well and this computer still performs acceptably (it's an ASUS P5B with an Intel QX6700 not overclocked with 6Gb of RAM). It doesn't have as much spec as modern computers but I'm amazed that this thing still feels like the day I got it.

There are 2 types of SATA headers on my board. Six SATA 3Gb/s ports and one JMicron RAID SATA port. I also bought and installed a HighPoint Rocket 620A 6Gb/s SATA PCIex1 adapter.

I tried some tests with the SSD (numbers are hdparm buffered disk reads):

Plugged into the PCIe adapter: 193Mb/s.
Plugged into the JMicron motherboard port: 135Mb/s.
Plugged into one of the size main SATA ports: The BIOS wouldn't recognise the drive at all, it wouldn't even get to the setup screen.

I don't have any special drivers installed, everything seems to work out of the box. While there aren't specific kernel options for the PCIe adapter it works ok. The docs says that Linux support is automatic.

While the performance of the SSD isn't as good as I expected, it's still noticeably faster than the RAID10 10,000 rpm SATA array I use. I think I'll put this one down to the motherboard being old and not supporting the faster transport speeds. I intentionally bought what was supposed to be a very high performing SSD. Oh well...

I am uneasy moving from RAID10 to non RAID so for piece of mind I will set up an rsync job to run twice a day to copy from the SSD to the RAID10 (which will have plenty of space).

[eccerr0r]

The sequential speeds is not the only advantage of an SSD. The random read speeds is what really makes an SSD shine. But you'll need to get at least some sort of x4 PCIe card to see higher sequential speeds on that motherboard and plug it into an x4 slot. The x1 won't cut it.
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?

[allistarM]

Thanks. I have noticed a general performance improvement with the SSD. I have moved /var to the RAID10 spinning array as well as large file storage (the SSD is only 240Gb). Odd that an SATA 6Gb/s card is only PCIe-x1 when that won't deliver the speeds needed for full SATA3 speed.