Re: Pathetic SATA performance
> On Thu, Feb 01, 2007 at 08:34:20PM -0000, Pete Clarke wrote:
>> Hi there,
>>
>> I have a file server, running Etch, with the following specs:
>>
>> P4, 1.7Ghz
>> 512MB Ram
>> 2 x SI based SATA I controllers
>> 4 x Maxtor 250GB SATA drives
>>
>> It is set up with software RAID 5, and the overall performance is
>> terrible.
>>
>> Every time it reboots (which happens due to dodgy power!), it does a
>> RAID
>> resync, this takes up 90% CPU time (for md0_resync process) for 50
>> hours!!
>> During this time, ANY access to the drive is painful.
>>
>> Now, I expected software RAID 5 to be slow, but not this bad - this is
>> the
>> reading from hdparm:
>>
>> bungo:~# hdparm -tT /dev/md0
>>
>> /dev/md0:
>> Timing cached reads: 2 MB in 4.71 seconds = 435.05 kB/sec
>> Timing buffered disk reads: 8 MB in 3.13 seconds = 2.56 MB/sec
>>
>>
>> Bad eh?
>>
>> Becuase they're SATA drives, hdparm cannot tune them - or indeed read
>> their
>> current settings. Is there any way I can speed this beast up, if not I
>> am
>> going to go back to my old PPro200-based file server, running SCSI->FCAL
>> bridge.
>>
>
> Wow, that is awful.
>
> I dont' do raid5 since I only have two disks.
>
> Two identical Seagate Barracuda 7200 80 GB SATA drives (with the SATA I
> rate limiting jumper removed), on my Asus MB nVidia chipset SATA-II
> ports. Each drive has three partitions, to for raid1, one for LVM.
>
> hdparm -tT /dev/md0
>
> /dev/md0
> Timing cached reads: 2424 MB in 2.00 seconds = 1212.23 MB/sec
> Timing buffered disk reads: 62 MB in 0.84 seconds = 73.44 MB/sec.
>
> What happens if you time the raw drives instead of md0? For me on raid1,
> its basically the same. I'm wondering if one or more of your drives are
> in difficulty and its slowing down the whole array.
>
> What does smartmontools say about the drive's S.M.A.R.T.s?
>
I get:
bungo:~# smartctl --all /dev/sda
smartctl version 5.36 [i686-pc-linux-gnu] Copyright (C) 2002-6 Bruce Allen
Home page is http://smartmontools.sourceforge.net/
Device: ATA ST3250620AS Version: 3.AA
Serial number: 9QE0MLDS
Device type: disk
Local Time is: Thu Feb 1 22:14:32 2007 GMT
Device does not support SMART
Error Counter logging not supported
[GLTSD (Global Logging Target Save Disable) set. Enable Save with '-S on']
Device does not support Self Test logging
As for individual drive performance :
bungo:~# hdparm -tT /dev/sda
/dev/sda:
Timing cached reads: 322 MB in 2.00 seconds = 160.99 MB/sec
Timing buffered disk reads: 106 MB in 3.00 seconds = 35.29 MB/sec
bungo:~# hdparm -tT /dev/sdb
/dev/sdb:
Timing cached reads: 348 MB in 2.01 seconds = 173.30 MB/sec
Timing buffered disk reads: 4 MB in 4.62 seconds = 886.44 kB/sec
bungo:~# hdparm -tT /dev/sdc
/dev/sdc:
Timing cached reads: 320 MB in 2.00 seconds = 159.67 MB/sec
Timing buffered disk reads: 36 MB in 5.39 seconds = 6.67 MB/sec
bungo:~# hdparm -tT /dev/sdd
/dev/sdd:
Timing cached reads: 342 MB in 2.01 seconds = 170.41 MB/sec
Timing buffered disk reads: 4 MB in 4.29 seconds = 954.93 kB/sec
Rather poo ...
I *must* be doing something wrong .. I can't believe SATA performance is
*THIS BAD*...
Cheers,
Pete.
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