lkml.org 
[lkml]   [2007]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: SATA RAID5 speed drop of 100 MB/s
Don't forget about max_sectors_kb either (for all drives in the SW RAID5 
array)

max_sectors_kb = 8
$ dd if=/dev/zero of=file.out6 bs=1M count=10240
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 55.4848 seconds, 194 MB/s

max_sectors_kb = 16
$ dd if=/dev/zero of=file.out5 bs=1M count=10240
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 37.6886 seconds, 285 MB/s

max_sectors_kb = 32
$ dd if=/dev/zero of=file.out4 bs=1M count=10240
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 26.2875 seconds, 408 MB/s

max_sectors_kb = 64
$ dd if=/dev/zero of=file.out2 bs=1M count=10240
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 24.8301 seconds, 432 MB/s

max_sectors_kb = 128
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 22.6298 seconds, 474 MB/s


On Sun, 24 Jun 2007, Dr. David Alan Gilbert wrote:

> * Michael Tokarev (mjt@tls.msk.ru) wrote:
>
> <snip>
>
>> By the way, I did some testing of various drives, and NCQ/TCQ indeed
>> shows some difference -- with multiple I/O processes (like "server"
>> workload), IF NCQ/TCQ is implemented properly, especially in the
>> drive.
>>
>> For example, this is a good one:
>>
>> Single Seagate 74Gb SCSI drive (10KRPM)
>>
>> BlkSz Trd linRd rndRd linWr rndWr linR/W rndR/W
>
> <snip>
>
>> 1024k 1 83.1 36.0 55.8 34.6 28.2/27.6 20.3/19.4
>> 2 45.2 44.1 36.4/ 9.9
>> 4 48.1 47.6 40.7/ 7.1
>>
>> The tests are direct-I/O over whole drive (/dev/sdX), with
>> either 1, 2, or 4 threads doing sequential or random reads
>> or writes in blocks of a given size. For the R/W tests,
>> we've 2, 4 or 8 threads running in total (1, 2 or 4 readers
>> and the same amount of writers). Numbers are MB/sec, as
>> totals (summary) for all threads.
>>
>> Especially interesting is the very last column - random R/W
>> in parallel. In almost all cases, more threads gives larger
>> total speed (I *guess* it's due to internal optimisations in
>> the drive -- with more threads the drive has more chances to
>> reorder commands to minimize seek time etc).
>>
>> The only thing I don't understand is why with larger I/O block
>> size we see write speed drop with multiple threads.
>
> My guess is that something is chopping them up into smaller writes.
>
>> And in contrast to the above, here's another test run, now
>> with Seagate SATA ST3250620AS ("desktop" class) 250GB
>> 7200RPM drive:
>>
>> BlkSz Trd linRd rndRd linWr rndWr linR/W rndR/W
>
> <snip>
>
>> 1024k 1 78.4 34.1 33.5 24.6 19.6/19.5 16.0/12.7
>> 2 33.3 24.6 15.4/13.8
>> 4 34.3 25.0 14.7/15.0
>>
>
> <snip>
>
>> And second, so far I haven't seen a case where a drive
>> with NCQ/TCQ enabled works worse than without. I don't
>> want to say there aren't such drives/controllers, but
>> it just happen that I haven't seen any.)
>
> Yes you have - the random writes with large blocks and 2 or 4 threads
> is significantly better for your non-NCQ drive; and getting more
> significant as you add more threads - I'm curious what happens
> on 8 threads or more.
>
> Dave
> --
> -----Open up your eyes, open up your mind, open up your code -------
> / Dr. David Alan Gilbert | Running GNU/Linux on Alpha,68K| Happy \
> \ gro.gilbert @ treblig.org | MIPS,x86,ARM,SPARC,PPC & HPPA | In Hex /
> \ _________________________|_____ http://www.treblig.org |_______/
> -
> To unsubscribe from this list: send the line "unsubscribe linux-ide" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-06-24 16:25    [W:0.079 / U:0.404 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site