At 11:16 -0400 14/9/07, Ross S. W. Walker wrote: >Yes, a write-back cache with a BBU will definitely help, also your config, The write-cache is enabled, but what I've not known up to now is that the absence of a BBU will impact IO performance in this way - which seems to be what you and Feizhou are saying. Is there any way to tell the card to forget about not having a BBU and behave as if it did? The main problem here is the latency when under IO load not the throughput (or lack of). I don't care if it can't achieve 300MB/s sustained write speeds, only that it shouldn't bring the machine to its knees in the process of getting 35MB/s. > > 4x Seagate ST3250820SV 250GB in a RAID 1 plus 2 hot spare config > >is kinda wasteful, why not create a 4 disk RAID10 and get a 5th drive for >a hot-spare. Logistics meant that it was more important to be able to cope with a disk failure without needing to visit the hosting centre immediately afterwards (which we'd have to do if there was only one hot spare). >Also think about getting 2 internal SATA drives for the OS and keep the >RAID10 as purely for data, that should make things humm nicely and to be >able to upgrade your data storage without messing with your OS/application >installation. It wouldn't cost a lot either, 2 SATA drives + 1 SAS drive. The server box is a Supermicro AS2020A - there is no onboard SATA nor any space for internal disks - there are 6 bays on a hot swap backplane and they're all cabled to the 3ware controller. I've unpacked and fired up one of the other identical machines and moved the drives from the original to this one and booted straight off them. The only difference between hardware is that the firmware on the 3Ware card in this one has not been updated (it's 3.04.00.005 from codeset 9.3.0 as opposed to 3.08.02.005 from 220.127.116.11). # /opt/iozone/bin/iozone -s 20480m -r 64 -i 0 -i 1 -t 1 Original box: Initial write 34208.20703 Rewrite 38133.20313 Read 79596.36719 Re-read 79669.22656 Newly unpacked box: Initial write 50230.10547 Rewrite 46108.17969 Read 78739.14844 Re-read 79325.11719 ... but the new one still shows the same IO blocking/responsiveness issue. S.