On Tue, 11 Jan 2000, Thomas Waldmann wrote:
> > Cable length is not so much a pain as the number of cables. Of course with
> > scsi you want multiple channels anyway for performance, so the situation
> > is very similar to ide. A cable mess.
>
> Well, it is at least only a half / third / ... of the cable count of "tuned"
> single-device-on-a-cable EIDE RAID systems (and you donīt have these big
> problems with cable length).
>
> I didnīt try LVD/U2W SCSI yet, but using UW SCSI you can put e.g. 2 .. 3 IBM
> DNES 9GB on a single UW cable (these are FAST while being affordable each one
> does ~~15MB/s) without loosing too much performance.
>
> Did anybody measure how this is with U2W/LVD ?
>
> How is performance when putting e.g. 4, 6 or 8 IBM DNES 9GB LVD on a single
> U2W channel compared to putting them on multiple U2W channels ?
>
I do not know what kind of RAID level you are discussing, because
haven't followed the thread but here are some results for two IBM DMVS09V
drives on a single U2W channel with Linux software-RAID1 (with raid1 read
balance patch applied). These are tiotest results.
Size is MB, BlkSz is Bytes, Read and Write are MB/sec, Seeks are Seeks/sec
Machine Directory Size(MB) BlkSz Threads Read Write Seeks
----------- ----------- --------- ------- --------- ------ ------- -------
icesus-r1p /mnt/ 800 4096 1 25.649 15.296 315.806
icesus-r1p /mnt/ 800 4096 2 33.970 15.528 610.314
icesus-r1p /mnt/ 800 4096 3 37.360 15.684 541.071
icesus-r1p /mnt/ 800 4096 4 35.351 15.447 629.723
icesus-r1p /mnt/ 800 4096 5 41.068 15.285 632.911
icesus-r1p /mnt/ 800 4096 6 40.818 15.131 624.352
icesus-r1p /mnt/ 800 4096 8 37.488 15.157 701.016
Not bad considering the bus was 40Mbytes/sec
Here are some info of the hardware:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: IBM Model: DMVS09V Rev: 0100
Type: Direct-Access ANSI SCSI revision: 03
Host: scsi0 Channel: 00 Id: 02 Lun: 00
Vendor: IBM Model: DMVS09V Rev: 0100
Type: Direct-Access ANSI SCSI revision: 03
Adaptec AIC7xxx driver version: 5.1.20/3.2.4
Compile Options:
TCQ Enabled By Default : Enabled
AIC7XXX_PROC_STATS : Disabled
AIC7XXX_RESET_DELAY : 5
Adapter Configuration:
SCSI Adapter: Adaptec AIC-7890/1 Ultra2 SCSI host adapter
Ultra-2 LVD/SE Wide Controller
PCI MMAPed I/O Base: 0xe3000000
Adapter SEEPROM Config: SEEPROM found and used.
Adaptec SCSI BIOS: Enabled
IRQ: 10
SCBs: Active 1, Max Active 24,
Allocated 30, HW 32, Page 255
Interrupts: 420588
BIOS Control Word: 0x10a6
Adapter Control Word: 0x1c5e
Extended Translation: Enabled
Disconnect Enable Flags: 0xffff
Ultra Enable Flags: 0x0000
Tag Queue Enable Flags: 0x0045
Ordered Queue Tag Flags: 0x0045
Default Tag Queue Depth: 8
Tagged Queue By Device array for aic7xxx host instance 0:
{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
Actual queue depth per device for aic7xxx host instance 0:
{8,1,8,1,1,1,8,1,1,1,1,1,1,1,1,1}
Statistics:
(scsi0:0:0:0)
Device using Wide/Sync transfers at 40.0 MByte/sec, offset 31
Transinfo settings: current(12/31/1/0), goal(12/31/1/0),
user(12/127/1/0)
Total transfers 194067 (98491 reads and 95576 writes)
(scsi0:0:2:0)
Device using Wide/Sync transfers at 40.0 MByte/sec, offset 31
Transinfo settings: current(12/31/1/0), goal(12/31/1/0),
user(10/127/1/0)
Total transfers 200068 (103008 reads and 97060 writes)
read_ahead 1024 sectors
md0 : active raid1 sdb1[1] sda1[0] 4417728 blocks [2/2] [UU]
md1 : active raid1 sdb2[1] sda2[0] 4538240 blocks [2/2] [UU]
unused devices: <none>
