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gentoorockerfr
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PostPosted: Mon Jun 04, 2012 3:44 pm    Post subject: Ocz agility3 low speed (SSD) Reply with quote

Hello ,
these are the results/infos i took from terminal
hdparm -Tt /dev/sdb
Code:

/dev/sdb:
Timing cached reads: 7420 MB in 2.00 seconds = 3711.45 MB/sec
Timing buffered disk reads: 500 MB in 3.01 seconds = 165.85 MB/sec


it have to be like this

Code:
Timing cached reads: 27738 MB in 2.00 seconds = 13889.38 MB/sec
Timing buffered disk reads: 1158 MB in 3.01 seconds =385.08 MB/sec


Why?How can i solve it?
The disk is like a normal.
I am waiting for your help
thank you
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whiteghost
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PostPosted: Mon Jun 04, 2012 6:45 pm    Post subject: Reply with quote

from my agility 2 60G
Code:
# hdparm -Tt /dev/sda

/dev/sda:
 Timing cached reads:   7528 MB in  2.00 seconds = 3764.76 MB/sec
 Timing buffered disk reads: 638 MB in  3.01 seconds = 212.20 MB/sec


Quote:
Timing cached reads: 27738 MB in 2.00 seconds = 13889.38 MB/sec
Timing buffered disk reads: 1158 MB in 3.01 seconds =385.08 MB/sec

sounds ridiculous to me
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gentoorockerfr
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PostPosted: Tue Jun 05, 2012 4:53 pm    Post subject: Reply with quote

https://wiki.archlinux.org/index.php/SSD_Benchmarking#OCZ-AGILITY3_120GB
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gentoorockerfr
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PostPosted: Thu Jun 07, 2012 4:19 pm    Post subject: Reply with quote

Any help please?
@whiteghost
PostPosted: Mon Jun 04, 2012 6:45 pm Post subject:
from my agility 2 60G
Code:
# hdparm -Tt /dev/sda

/dev/sda:
Timing cached reads: 7528 MB in 2.00 seconds = 3764.76 MB/sec
Timing buffered disk reads: 638 MB in 3.01 seconds = 212.20 MB/sec
so you are faster than me and you have agility 2!
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WorBlux
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PostPosted: Thu Jun 07, 2012 5:19 pm    Post subject: Reply with quote

Just curious, what sort of motherboard do you have?
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PostPosted: Thu Jun 07, 2012 7:34 pm    Post subject: Reply with quote

do you have a sata 3 connection?

i've never seen anyone match the benchmark posted at archlinux forum, so i am skeptical.

i use a desktop and have lots of memory and hdd.

so i mount /var/tmp/portage and /tmp tmpfs in fstab.

i make my distfiles directory /distfiles and mount on a hdd.

i used to not use swap but have recently made swap on hdd.

i use gparted to partition and it has option to align to MiB

use ahci driver and try not to fill over 70 %

http://www.ocztechnologyforum.com/forum/showthread.php?97693-is-certain-amount-of-free-space-required-for-optimal-performance

that is about all you can do.

while i have gone to lengths to avoid writes a person also should not be afraid to use their ssd. it should last a long time.
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eccerr0r
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PostPosted: Fri Jun 08, 2012 12:28 am    Post subject: Reply with quote

Not same machine or disk, but numbers are very possible... but machine dependent.

Code:
Timing cached reads: 29206 MB in 2.00 seconds = 14624.82 MB/sec
Timing buffered disk reads: 1128 MB in 3.00 seconds = 375.98 MB/sec


Not using the same disk, but still SSD: Core i7/z68/SSD520

Yes, SATA3 (6Gb/sec) is needed to get this high... Make sure you're using a good cable and a SATA3 port. There's only 2 on my z68 board...
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whiteghost
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PostPosted: Fri Jun 08, 2012 2:27 am    Post subject: Reply with quote

eccerr0r wrote:
Not same machine or disk, but numbers are very possible... but machine dependent.

Code:
Timing cached reads: 29206 MB in 2.00 seconds = 14624.82 MB/sec
Timing buffered disk reads: 1128 MB in 3.00 seconds = 375.98 MB/sec


Not using the same disk, but still SSD: Core i7/z68/SSD520

Yes, SATA3 (6Gb/sec) is needed to get this high... Make sure you're using a good cable and a SATA3 port. There's only 2 on my z68 board...


i looked at the specs for agility 3 and intel 520 at newegg, very close.
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gentoorockerfr
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PostPosted: Sun Jun 10, 2012 4:32 pm    Post subject: Reply with quote

my specs
AMD Phenom(tm) II X4 955 Processor
ASRock 890GM Pro3 R2.0
6gb ddr3 1600 ram
i think <<good>> sata cable and sata 3 port..
and the disk has 35% available space
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gentoorockerfr
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PostPosted: Tue Jun 19, 2012 12:59 pm    Post subject: Reply with quote

So any help please?Whats the error-problem?
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PostPosted: Tue Jun 19, 2012 2:28 pm    Post subject: Reply with quote

gentoorockerfr wrote:
So any help please?Whats the error-problem?


ASRock Z68 Pro3-M, SAMSUNG 470 64.0GB

hdparm -Tt /dev/sda

/dev/sda:
Timing cached reads: 20418 MB in 2.00 seconds = 10220.55 MB/sec
Timing buffered disk reads: 706 MB in 3.00 seconds = 234.96 MB/sec

PCI bridge: ASMedia Technology Inc. ASM1083/1085 PCIe to PCI Bridge
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eccerr0r
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PostPosted: Tue Jun 19, 2012 3:12 pm    Post subject: Reply with quote

I do have to say something is strange - how old is the AsRock 890GM board?
It's weird that it has 5 SATA 6Gb ports but my Z68 (Gigabyte Z68AP-D3) only has two... Apparently Intel thinks sata 6Gb ports are hard to attach and therefore only offers 2... Not sure if it's the motherboard limiting the speed or not.

How are the SATA6Gb attached to the cpu, does it go through the southbridge (bad)? When you're using hdparm to test, it should not care about fragmentation much, as fragmentation really affects small writes.

steffie: what CPU do you have? Curious how much the CPU determines the cached read speeds versus the chipset/disk...
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gentoorockerfr
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PostPosted: Tue Jun 19, 2012 3:31 pm    Post subject: Reply with quote

My motherboard is this
http://www.asrock.com/mb/overview.asp?model=890gm%20pro3%20r2.0


How are the SATA6Gb attached to the cpu, does it go through the southbridge (bad)? When you're using hdparm to test, it should not care about fragmentation much, as fragmentation really affects small writes.

could you explain it?
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PostPosted: Tue Jun 19, 2012 4:02 pm    Post subject: Reply with quote

When you partitioned the drive did you ensure it was aligned to 4k as oppose to 512?
by default fdisk will partition assuming a 512b sector size, which is valid for old HDD

Newer HDD as well as SSD have sector sizes of 4096 (so they don't run out of indexing). Thing is if you partition the drive without taking this into consideration and the partition/s are NOT aligned to these clusters you end up in a situation where reads/writes require spanning 2 sectors to complete resulting in additional commands being issued to the controller
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gentoorockerfr
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PostPosted: Tue Jun 19, 2012 5:25 pm    Post subject: Reply with quote

Code:
fdisk /dev/sdb1
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0xd52ef117.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)



Code:

fdisk -lu /dev/sdb

Disk /dev/sdb: 60.0 GB, 60022480896 bytes
255 heads, 63 sectors/track, 7297 cylinders, total 117231408 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000550b3

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048   117229567    58613760   83  Linux


So whats my next move?
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eccerr0r
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PostPosted: Tue Jun 19, 2012 9:13 pm    Post subject: Reply with quote

The port connection issue is very technical but it boils down to the latency and bottlenecks involved when passing data through the channels. Now I don't know too much about AMD Hypertransport unfortunately, only have some rudimentary knowledge about Intel QPI, but I have to assume they have some similarities. The SATA controllers can be connected to the first level QPI where bandwidths are highest but there are a limited number of connections. One possibility to increase the number of connections is to put it on a bridge to multiplex more connections, usually the southbridge. There's latency and delays involved there which will slow down throughput.

The sector fragmentation is an interesting possibility but if you hdparm on the raw device like /dev/sda, etc., this should be aligned to the first sector/sector 0, which should be aligned to any sector size, or at least I would hope it to be the case... With newer versions of fdisk starting at sector 2048 this should be aligned to 4096 byte-sectors as long as your partitions are a multiple of 4096 bytes.
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gentoorockerfr
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PostPosted: Wed Jun 20, 2012 11:25 am    Post subject: Reply with quote

can i change alignment to 4k without delete/format the disk?


ps so the problem exist because disk's alignment?512b instead of 4k?
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PostPosted: Wed Jun 20, 2012 1:08 pm    Post subject: Reply with quote

I think it already is, but you can't really redo without erasing everything (though gparted might be able to do something).

Start sector 2048 (versus 63, because old versions of fdisk aligned to "track" which makes sense for very old disks) is a multiple of 4096 since 2048*512 is a multiple of 4096 - it's the 256th 4096 sector.

I'm still convinced it's a motherboard issue at the moment.
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gentoorockerfr
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PostPosted: Wed Jun 20, 2012 4:47 pm    Post subject: Reply with quote

could you tell me please how to format a ssd disk to have full performance.What about gptfdisk?
Also what these lines said?
255 heads, 63 sectors/track, 7297 cylinders, total 117231408 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


ps how could i overtake motheboard issue?
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PostPosted: Wed Jun 20, 2012 7:20 pm    Post subject: Reply with quote

Code:

fdisk -lu /dev/sdb

Disk /dev/sdb: 60.0 GB, 60022480896 bytes
255 heads, 63 sectors/track, 7297 cylinders, total 117231408 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000550b3

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048   117229567    58613760   83  Linux

See that looks like 512b blocksize.



cat /sys/block/sda/queue/physical_block_size
4096
cat /sys/block/sda/queue/logical_block_size
512
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gentoorockerfr
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PostPosted: Wed Jun 20, 2012 8:39 pm    Post subject: Reply with quote

yes...

Code:
cat /sys/block/sda/queue/physical_block_size
512
cat /sys/block/sda/queue/logical_block_size
512

why..
i think that i partioned this disk with gparted...

could you tell me please how to format a ssd disk to have full performance.What about gptfdisk?
whats next move?
thank you for your time
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PostPosted: Thu Jun 21, 2012 12:47 am    Post subject: Reply with quote

Motherboard issue meaning: replace motherboard with another brand and/or newer chipset that has the SATA ports attached differently to hypertransport.

This is if you're sure you're using the correct driver for the SATA chipset.

Granted I don't know enough about AMD bus structures and chipsets (other than the fact that my AthlonXP + SiS and AthlonXP + nVidia chipset systems seem a little slow to PATA IDE cache), but the Intel Z68 seems to do fine...
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gentoorockerfr
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PostPosted: Sun Jun 24, 2012 5:55 pm    Post subject: Reply with quote

so there is not any problem because of 512b alignment of my ssd?
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PostPosted: Sun Jun 24, 2012 6:41 pm    Post subject: Reply with quote

gentoorockerfr wrote:
so there is not any problem because of 512b alignment of my ssd?

if you are convinced sure.

http://www.osnews.com/story/22872/Linux_Not_Fully_Prepared_for_4096-Byte_Sector_Hard_Drives


There are lots of litature out there detailing why having an unaligned can cause issues
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PostPosted: Wed Jun 27, 2012 1:28 pm    Post subject: Reply with quote

Imagine if hard drives "Bus Errors" when someone does an unaligned access...

(sorry about this bad, obscure joke related to how some CPUs will bus error when doing unaligned accesses. Once again this is a performance related issue on CPUs too! Then again the bus errors were meant to make people rewrite their code, maybe we need to do this for HDDs too...)
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