(Solved) Weird drop of hard disk performance!

[Apopatos]

Hi guys,
I bought a new hard disk and installing gentoo.
When I compiled my kernel and booted it was as fast as a dream. The T option of hdparm gave about 1000 MB/s. I continued to emerge software when suddenly, after few hours, I noticed a slowness to both my hard disks. hdparm now gives:
/dev/sda
Timing cached reads: 467.15 MB/s

/dev/sdb
Timing cached reads: 464.44 MB/s

Which menas it dropped by 50% :S

I tried the livecd and I got 946.62 MB/s for sda and 971.22 MB/s for sdb. These are normal numbers I used to get to my original system few hours ago.
I chrooted to my system and the numbers dropped again to: 499.87 and 499.55 MB/s.

Weird! Isn't it?
Any idea guys?

(sorry for writing like this but I'm posting from command line and is difficult to copy-paste, insert code etc)

[Urban Cowboy]

From what I understand, I think hdparm only really works well for IDE devices. Not so much for SATA or SCSI.

Also, during LiveCD use, I think most of the stuff being used by the computer is read off the CD or is stored in the RAM, making it much faster.

For SCSI and SATA disks, try using sdparm
_________________
Anything worth doing is worth over-doing. Moderation is for cowards.

[Apopatos]

400MB/s are too low even if hdparm works well or not. The hard disks delay a lot, it's obvious when I use them.
I tried my second drive to another computer with different distribution. It gives 995+ Mb/s as my gentoo used to do few hours ago. :S

[eccerr0r]

Make sure your versions of hdparm are the same for both before and after, or better yet, use the same binary.

Version 6.9 of hdparm made a large calculation difference in cached speeds.
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?

[Apopatos]

Indeed in the live cd there is hdparm 6.6. I Have 7.7 but there isn't an ebuild previous than 7.7. Where can I find one?
Here there is 7.7 as well:
http://tinderbox.dev.gentoo.org/html/default-linux/amd64/hdparm-7.7.html

[eccerr0r]

for the most part, if you take a pre-6.9 version's result and approximately divide by 2, that's what the post 6.9 binary would generate for may older machines. For newer machines it will produce a higher number.

The cached reads number is fairly inconsequential, what are your relative (from run to run)
- Buffered disk reads
- Bogomips
- DMA settings

Those will have a larger impact of your machine.

The thing that I'm suspecting now is that you installed the 6.6 version of hdparm from the livecd and tested it, then during the install you picked up the latest version, 7.7, and your speed went "down" when it really just was counted differently.
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?

[Apopatos]

But my system is significantly slower now. emerge needs a lot of time when it was much faster before and the video thumbnails are generated much slower now plus both the hard disks are noisy while before weren't at all!

[Apopatos]

Ok I installed version 6.6. "Timing cached reads" is improved the noises stays and when I try copy many big files (over one GB) from sdb to sda and vice versa they "run" with 50-60 mb/s but after few minutes it drops to 10-20mb/s. Is that normal?
Every partition is in reiserfs.

[drescherjm]

[drescherjm]

[eccerr0r]

run 'top' and see if there are any processes running in the background.

There's no reason to run hdparm-6.6, all it is - is an epeen boost with a larger number...

What CPU are you running?
Most Core2 chips should be in the Gbyte/s range for cached reads.

These are all with hdparm-7.7 for comparison, but it looks like this is not your issue since you got the same number with hdparm-6.6 when the machine is in "slow" mode.

My 1.8GHz athlon is slow (and may be an issue, could anyone compare? 256K L2, SiS735 chipset):
Timing cached reads: 538 MB in 2.01 seconds = 268.23 MB/sec

My 1.6GHz Pentium-M is also fairly low (2M L2):
Timing cached reads: 1162 MB in 2.00 seconds = 580.39 MB/sec

My 1.3GHz Madison is a bit higher (3M L2):
Timing cached reads: 2444 MB in 2.00 seconds = 1222.59 MB/sec

My 2.6GHz Core2 is ludicrous (4M L2):
Timing cached reads: 7032 MB in 2.00 seconds = 3518.92 MB/sec
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?

[Apopatos]

Thank you very much guys for your answers.
Indeed there isn't any change to the speed of the hard disk if I try hdparm 6.6 or 7.7 but the displayed numbers.
Now why sometimes when I copy large files the speed is less than 20 mb/s and sometimes over 50, I can't figure out.

I have athlon64 3000+ with 64bit installed gentoo. RAM 768 and filesystem reiserfs.
My hard disks are two Seagate Barracuda. 500GB with 32 mb cache and 320 GB with 16mb cache.

[eccerr0r]

when it's running at 50MB/sec and then 20MB/sec, are you measuring through 'cp' or 'hdparm'?

When the machine is running at 50MB/sec, what does hdparm -t /dev/sda report, and when it's running slow, the same?

When you run 'top' do you see anything running in the background such as updatedb?
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?

[Apopatos]

[eccerr0r]

All filesystems will slow down a bit for small files; but the specialty of reiserfs is that it will consume CPU cycles for small files as it will pack the small files better.

Small files are files less than one block, so more like 0 bytes to probably around 16K bytes. Do you have a lot of these?

hdparm should virtually report the same speed all the time since it does not use files. If you see hdparm dropping, then this is unexpected behavior.

Mark your topic with [Solved] if you're now sure this is what's happening...
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?