[linux-lvm] LVM performance questions..
Eric Whiting
ewhiting at amis.com
Fri Mar 10 15:41:07 UTC 2000
I've been watching the LVM stuff for a long time. I finally gave it a
try this week. I really like the tools. I think it is a great thing
for Linux.. Thanks.
I have some performance questions. I was expecting to see some speed
increase for a LVM stripe, but I didn't. Is there someone out there
who has had more experience with this that can point me in the right
direction? I found that the LVM stripe is running the same write
speeds as a single disk and the same as a md RAID0 set. Sure feels
like a Hardware problem, but I'm not sure.
I threw 2 9G 10k RPM disks into a VG. Then I created a 12G LV in
stripe mode (at least I think I had it set right). I did a simple
dd write benchmark. 25M/s (for a 1000M file). Then I tried a solo
drive. 25M/s as well. I'm confused by the performance numbers -- on
our Suns with SW raid we improve speed somewhat linear as we add
drives
to a raid0 set. I redid the LV with stripsize of 16k and 256k. No
difference in performance. Could my SCSI bus be killing me? My boot
log shows this:
<6>sym53c876-0-<0,*>: FAST-20 WIDE SCSI 40.0 MB/s (50 ns, offset 16)
<4>SCSI device sda: hdwr sector= 512 bytes. Sectors= 17773524 [8678
MB] [8.7 GB]
Any scsi experts out there? I did scsiinfo -i /dev/sdb and saw the 32
bit bus not set... I'm not sure if that matters or not.. Am I looking
the wrong place for problems.
Inquiry command
---------------
Relative Address 0
Wide bus 32 0
Wide bus 16 1
Synchronous neg. 1
Linked Commands 1
Command Queueing 1
ko /home/ewhiting> cat /proc/lvm
LVM driver version 0.8i (02/10/1999)
Total: 1 VG 2 PVs 1 LV (1 LV open 1 times)
Global: 53225 bytes vmalloced IOP version: 5 2 days 17:49:02
active
VG: oracle_vg [2 PV, 1 LV/1 open] PE Size: 4096 KB
Usage [KB/PE]: 17768448 /4338 total 12582912 /3072 used 5185536
/1266 free
PVs: [AA] /dev/sdb1 8884224 /2169 6291456 /1536
2592768 /633
[AA] /dev/sdc1 8884224 /2169 6291456 /1536
2592768 /633
LV: [AWDS2 ] oracle_lv 12582912 /3072 1x open
eric
--
__________________________________________________________________
Eric T. Whiting AMI Semiconductors
(208) 234-6717 2300 Buckskin Road
(208) 234-6659 (fax) Pocatello,ID 83201
ewhiting at poci.amis.com
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