From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <38C91793.AD7815DE@amis.com> Date: Fri, 10 Mar 2000 08:41:07 -0700 From: Eric Whiting MIME-Version: 1.0 Subject: [linux-lvm] LVM performance questions.. Content-Transfer-Encoding: 7bit Sender: owner-linux-lvm Errors-To: owner-linux-lvm List-Id: Content-Type: text/plain; charset="us-ascii" To: linux-lvm@msede.com 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@poci.amis.com