Arch Linux

fr33

Member

Registered: 2008-03-23

Posts: 3

worry about disk speed

Hello,
i am using arch almost for a year but i suddenly found myself newbie in hardware .
At work i have SUN fire X4200, M2 2x DualCore AMD Opteron 2216, 2400 MHz, 4 Gb RAM, 2x Seagate ST973401LSUN72G SAS drives.
So i created hardware raid 0 so in total i have 146 Gb. So i tried to run hdparm -t /dev/sda  :
/dev/sda:
Timing cached reads:   1760 MB in  2.00 seconds = 880.32 MB/sec
Timing buffered disk reads:  350 MB in  3.00 seconds = 116.56 MB/sec
Surprisingly I expected much bigger buffered disk read, perhaps nearly ~200 MB/sec.
Correct me if i am wrong but shouldn't be bigger?
Thanks

iBertus

Member

From: Greenville, NC

Registered: 2004-11-04

Posts: 2,228

Re: worry about disk speed

These numbers are for the first machine in my sig, with regular SATA 3.0 drives. RAID 1 is being used for redundancy.

/dev/sda:
 Timing cached reads:   7430 MB in  2.00 seconds = 3718.69 MB/sec
 Timing buffered disk reads:  236 MB in  3.02 seconds =  78.14 MB/sec

fr33

Member

Registered: 2008-03-23

Posts: 3

Re: worry about disk speed

These numbers are for the first machine in my sig, with regular SATA 3.0 drives. RAID 1 is being used for redundancy.

/dev/sda:
 Timing cached reads:   7430 MB in  2.00 seconds = 3718.69 MB/sec
 Timing buffered disk reads:  236 MB in  3.02 seconds =  78.14 MB/sec

Actually i don't need data redundancy i need speed

cerbie

Member

Registered: 2008-03-16

Posts: 124

Re: worry about disk speed

Since the days DMA took off, SCSI drives have rarely been that much faster at normal reads and writes. Then, those are not the fastest of their kind (10k), and smaller than normal (2.5").

One one hand, hdparm isn't going to show them in their best light. On the other, if you need raw transfer speed, more cheap drives are going to give you more. Any nice SCSI drive will have an edge when it's really getting beaten, but not plain old file copying.

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"If the data structure can't be explained on a beer coaster, it's too complex." - Felix von Leitner

schivmeister

Developer/TU

From: Singapore

Registered: 2007-05-17

Posts: 971

Website

Re: worry about disk speed

Timing buffered disk reads:  104 MB in  3.04 seconds =  34.25 MB/sec

2.5" 5400RPM

$ dd if=/dev/zero of=diskbench.1G bs=1024 count=1000000
# time cp diskbench.1G /

Then copy that between other directories, partitions, disks and do the math. 5400RPM is dead slow, barely managing 25 MB/sec

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I need real, proper pen and paper for this.

loosec

Member

Registered: 2007-03-08

Posts: 134

Re: worry about disk speed

Is your raid set really named /dev/sda ?

fr33

Member

Registered: 2008-03-23

Posts: 3

Re: worry about disk speed

Is your raid set really named /dev/sda ?

Yes it is /dev/sda.