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  #1  
Old 10th April 2008, 03:27 PM
JohnnyChre Offline
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Join Date: Feb 2008
Location: Quebec
Age: 34
Posts: 24
Slow IDE performance

Hi All.

HP Vectra VL420
CPU: 1.7gig
RAM: 768meg
HD: IDE Seagate ATA/100

I'm running Fedora 8 with a 20gig IDE Drive that support UDMA5 ATA/100. This box is a Squid Server with Squidguard.

I'm currently in test and with 5-10 users and I see a lot of CPU %wa time when a user do a request that is not in memory.


I have some performance issue when I see the %wa time high. I'm sure that my hard drive is the bottleneck.

hdparm -i /dev/sda
Model=ST320011A , FwRev=3.10 , SerialNo=3HT0PENS
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs RotSpdTol>.5% }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
BuffType=unknown, BuffSize=2048kB, MaxMultSect=16, MultSect=?16?
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=39851760
IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5
AdvancedPM=no WriteCache=enabled
Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5

* signifies the current active mode

hdparm -v /dev/sda

/dev/sda:
IO_support = 0 (default 16-bit)
readonly = 0 (off)
readahead = 256 (on)
geometry = 2480/255/63, sectors = 39851760, start = 0

hdparm -tT /dev/sda

/dev/sda:
Timing cached reads: 442 MB in 2.01 seconds = 220.37 MB/sec
Timing buffered disk reads: 124 MB in 3.04 seconds = 40.74 MB/sec

Why I only get 40...MB/sec ? Is it normaly with my drive ?

My drive is a ATA/100, normally I'm supposed to do something better like 90MB/sec ? No ??

I tried to play with the hdparm -c ... -d ... parameter and always get an error that it is not allowed

hdparm -d1 /dev/sda

/dev/sda:
setting using_dma to 1 (on)
HDIO_SET_DMA failed: Inappropriate ioctl for device
[root@Proxy ~]# hdparm -c1 /dev/sda

/dev/sda:
setting 32-bit IO_support flag to 1
HDIO_SET_32BIT failed: Invalid argument
IO_support = 0 (default 16-bit)

Can someone help me ?

I need to put this Squid server in production in two weeks and I think that it will not support the load of my 140 users.

Thanks

Jonathan
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  #2  
Old 10th April 2008, 08:17 PM
lazlow Offline
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Join Date: Aug 2005
Posts: 3,172
There is currently a physical limitation on HD speed rather than a interface speed. This is why it does not matter if a drive is sata1 or sata2 becuase no disk runs fast enough to outrun sataI (just using sata as an example).

Most relatively new drives will top out at about at about 75MB/sec. My 250gb WD IDE drive tests out at 60MB/sec. It was bought when the 250gb drives were in the sweet spot for price/performance (3 years ago?).

From the look of that model number I would guess that it is a 20gb drive. If it is, it is probably an older technology drive so 40 may be its physical limit.
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  #3  
Old 10th April 2008, 11:16 PM
JohnnyChre Offline
Registered User
 
Join Date: Feb 2008
Location: Quebec
Age: 34
Posts: 24
Hi.

Great explanation. I was thinking that because my drive is an ATA/100, it can do something near 80mb/sec.

I did a test this afternoon with an another model of computer and an another kind of hardrive and I cannot get a transfer speed over 40mb/sec.

I can understand that my current speed is not too bad.

Do you think that my current config will support 140 users ? I saw some configuration exemple on the web and some peoples was able to run squid for 400-500 users with a computer that have an older setup than mine.

I tried to put an another hard disk but still get a high %wa time when the website is big and the object are not in memory. Something like %wa = 45.

Thanks

Jonathan
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  #4  
Old 10th April 2008, 11:28 PM
lazlow Offline
Registered User
 
Join Date: Aug 2005
Posts: 3,172
Best bet is just give it a try. IF it does not work I would not screw around, get a HARDWARE raid card (do not mess around with fakeraid or software raid cards) and run something like raid10. These types of raid spread each R/W operation across multiple drives. Assumeing you have a bunch of the same 20gig drives and you used six of them you would have 60gb of storage(the other 60gb would be mirrored storage) but you would have a throughput of about 100MB/sec. If you are not the concerned about backup you could also run Raid0. With raid zero you could have the same 60gb of storage, same 100MB/sec, but with only three 20gb drives(but if any one drive fails your loose them all).
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