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SubjectSlow SCSI perf in RH 7.3
I have a server:
2.4.20-28.7 #1 Thu Dec 18 11:31:59 EST 2003 i686

with SCSI hard disks (not raid):

SCSI subsystem driver Revision: 1.00
scsi0 : Adaptec AIC7XXX EISA/VLB/PCI SCSI HBA DRIVER, Rev 6.2.8
<Adaptec 3960D Ultra160 SCSI adapter>
aic7899: Ultra160 Wide Channel A, SCSI Id=7, 32/253 SCBs

scsi1 : Adaptec AIC7XXX EISA/VLB/PCI SCSI HBA DRIVER, Rev 6.2.8
<Adaptec 3960D Ultra160 SCSI adapter>
aic7899: Ultra160 Wide Channel B, SCSI Id=7, 32/253 SCBs

blk: queue dfdbe014, I/O limit 4095Mb (mask 0xffffffff)
Vendor: FUJITSU Model: MAP3367NP Rev: 5605
Type: Direct-Access ANSI SCSI revision: 03
blk: queue dfdbe214, I/O limit 4095Mb (mask 0xffffffff)
Vendor: FUJITSU Model: MAP3367NP Rev: 5605
Type: Direct-Access ANSI SCSI revision: 03
blk: queue dfdbe614, I/O limit 4095Mb (mask 0xffffffff)
Vendor: SEAGATE Model: ST373307LW Rev: 0005
Type: Direct-Access ANSI SCSI revision: 03
blk: queue dfdbea14, I/O limit 4095Mb (mask 0xffffffff)
scsi0:A:0:0: Tagged Queuing enabled. Depth 32
scsi0:A:1:0: Tagged Queuing enabled. Depth 32
scsi0:A:4:0: Tagged Queuing enabled. Depth 32
Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
Attached scsi disk sdb at scsi0, channel 0, id 1, lun 0
Attached scsi disk sdc at scsi0, channel 0, id 4, lun 0
(scsi0:A:0): 160.000MB/s transfers (80.000MHz DT, offset 127, 16bit)
SCSI device sda: 71132959 512-byte hdwr sectors (36420 MB)
Partition check:
sda: sda1 sda2 sda3 sda4 < sda5 sda6 sda7 sda8 sda9 >
(scsi0:A:1): 160.000MB/s transfers (80.000MHz DT, offset 127, 16bit)
SCSI device sdb: 71132959 512-byte hdwr sectors (36420 MB) sdb: sdb1
(scsi0:A:4): 160.000MB/s transfers (80.000MHz DT, offset 63, 16bit)
SCSI device sdc: 143374744 512-byte hdwr sectors (73408 MB) sdc: sdc1
Journalled Block Device driver loaded

used for graphic files server to Apples (via Netatalk 1.5.2-3) with ext3. OS
on one disk, data files on the other two. IDE removable storage.

It's great with only one user, but with multiple Apple users, it does a
passable impression of a boat anchor. Even ssh then comes back one character
at a time. Top shows nothing out the ordinary, I think. Here's some typical
'sar -b' stuff:

03:20:00 PM tps rtps wtps bread/s bwrtn/s
03:30:00 PM 3.97 1.97 2.00 75.65 37.09
03:40:00 PM 4.41 2.32 2.09 336.19 122.32
03:50:00 PM 2.93 1.87 1.05 326.00 131.52
04:00:00 PM 2.44 1.80 0.65 294.09 27.97
04:10:00 PM 2.16 0.58 1.57 107.37 53.69
04:20:00 PM 0.81 0.16 0.66 32.26 31.38
04:30:00 PM 1.78 0.72 1.06 84.34 94.09
04:40:00 PM 1.28 0.55 0.73 55.81 97.88
04:50:00 PM 0.69 0.21 0.48 3.78 13.29
05:00:01 PM 1.82 0.51 1.32 6.02 51.81
05:10:00 PM 1.22 0.04 1.18 0.72 89.07
05:20:00 PM 2.60 1.13 1.47 63.19 30.13
05:30:00 PM 1.36 0.31 1.05 3.44 46.59
Average: 2.51 1.57 0.94 42.79 32.36


which I wish I knew well enough to interpret. :-(

So, I'd like to do *something* to speed things up. The likely suspects are:

1) Tweak the kernel somehow, in the knowledge that I'll probably just make
things worse (caching?)

2) Buy RAID (which level do I want? Is SATA raid faster than SCSI non-raid?)

3) Buy nicer/more expensive hard disks on the current controller, or, perhaps,
a faster non-raid controller.

All the connections, terminators, etc. seem happy.

I would consider trading a little reliability for a lot of performance.

The inevitable omitted information upon request. I was hoping for some
suggestions from some very kind list members.

Thanks!

--
_________________________________________
Nachman Yaakov Ziskind, FSPA, LLM awacs@ziskind.us
Attorney and Counselor-at-Law http://ziskind.us
Economic Group Pension Services http://egps.com
Actuaries and Employee Benefit Consultants
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