Re: sata_sil24 stability and performance

[Denys Dmytriyenko <denis@denix.org>]

On Tue, Mar 04, 2008 at 12:28:06PM +0900, Tejun Heo wrote:
> > I am pretty much convinced at this point that my exceptions/resetting
> > problem is due to the PSU. I've been testing different configurations
> > lately and was able to get stable system powering 14 (!) drives by both
> > PSUs together. The limiting factor is Amps on a single +12V rail:
> > Coolermaster 750 limits single rail to 19A (6 drives @ 2.8A/drive) and
> > my old Enermax 550 has 24A limit (8 drives @ 2.8A/drive). Even though
> > Coolermaster 750 has 4 rails, the wiring is not optimal and only 1 rail
> > is available for the hard drives...
> > 
> > See item #8 here:
> > http://www.pcpower.com/technology/myths/
> 
> Ah... yeah, that's what I've been saying all along.  Fancy powers w/
> multiple 12v rails suck for storage array.  My 15$ no name single lane
> PSU works much better than 40$ dual lane one.

I've got the first exception (but not reset) in several days running in
the above configuration:

Mar  3 19:09:04 [kernel] ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
Mar  3 19:09:04 [kernel] ata1.00: irq_stat 0x00020002, device error via D2H FIS
Mar  3 19:09:04 [kernel] ata1.00: cmd ef/42:fe:00:00:00/00:00:00:00:00/40 tag 0 cdb 0x0 data 0
Mar  3 19:09:04 [kernel]          res 51/04:fe:00:00:00/00:00:00:00:00/40 Emask 0x1 (device error)
Mar  3 19:09:04 [kernel] ata1.00: configured for UDMA/100
Mar  3 19:09:04 [kernel] ata1: EH complete
Mar  3 19:09:04 [kernel] sd 0:0:0:0: [sda] 976773168 512-byte hardware sectors (500108 MB)
Mar  3 19:09:04 [kernel] sd 0:0:0:0: [sda] Write Protect is off
Mar  3 19:09:04 [kernel] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
Mar  3 19:09:04 [kernel] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

Is it something I should be worried about?

> > Tejun,
> > 
> > As one of the Gurus on this list, can you suggest any tweaks/settings
> > to try out to improve/resolve my 17 MB/s write speed limit?
> 
> How did you test?  W/ dd?  hdparm?

# hdparm -t /dev/sda

/dev/sda:
 Timing buffered disk reads:  170 MB in  3.03 seconds =  56.16 MB/sec

# dd if=/dev/zero of=file bs=100M count=20
20+0 records in
20+0 records out
2097152000 bytes (2.1 GB) copied, 117.053 s, 17.9 MB/s

# dd if=file of=file1 bs=100M count=20
20+0 records in
20+0 records out
2097152000 bytes (2.1 GB) copied, 161.721 s, 13.0 MB/s

# dd if=file of=/dev/null bs=100M count=20
20+0 records in
20+0 records out
2097152000 bytes (2.1 GB) copied, 34.6141 s, 60.6 MB/s

A similar drive in an ICH7 box shows more consistent results:

# hdparm -t /dev/sda

/dev/sda:
 Timing buffered disk reads:  182 MB in  3.01 seconds =  60.48 MB/sec

# dd if=/dev/zero of=file bs=100M count=100
100+0 records in
100+0 records out
10485760000 bytes (10 GB) copied, 242.908 s, 43.2 MB/s

# dd if=file of=/dev/null bs=100M count=100
100+0 records in
100+0 records out
10485760000 bytes (10 GB) copied, 211.132 s, 49.7 MB/s

Please let me know if you need more details/logs. Thanks in advance!

Regards,
Denys