Обсуждение: Re: FORGOT TO CONFIGURE RAID! DELL POWEREDGE 2950
Joseph wrote: > We just got a DELL POWEREDGE 2950. So I was tasked with putting > Linux Redhat and dumped our software/packages on it. Contrary to > common sense, I didn't bother reading the manuals that came with te > 2950. I went right ahead and installed Redhat server on it, then went > and loaded the backups software/data etc onto it and started having > the team use it. And this has to do with pgsql.performance exactly what? Anyway, as someone who seems to administrates a PostgreSQL production box, you sure have a good backup plan. So just call DELL's support, fix you RAID and restore form backup. From the DELL site it seems this `PERC 5/i' on board controller (assuming that's what you have) doesn't even have a BBU. If you don't plan to post here in a few weeks again about data corruption, go out and shop a serious controller. And before you move that box in production, check: Is my hardware and software setup fsync/fua clean? Is my backup plan working? -- Best regards, Hannes Dorbath
On Sat, Jul 14, 2007 at 10:29:05AM +0200, Hannes Dorbath wrote: > From the DELL site it seems this `PERC 5/i' on board controller > (assuming that's what you have) doesn't even have a BBU. If you don't > plan to post here in a few weeks again about data corruption, go out and > shop a serious controller. We have a 2950 with a PERC, and it has a BBU. /* Steinar */ -- Homepage: http://www.sesse.net/
"Hannes Dorbath" <light@theendofthetunnel.de> writes: > From the DELL site it seems this `PERC 5/i' on board controller > (assuming that's what you have) doesn't even have a BBU. If you don't > plan to post here in a few weeks again about data corruption, go out and > shop a serious controller. This is a bit of a strange comment. A BBU will improve performance but Postgres doesn't require one to guarantee data integrity. If your drives have write caching disabled (ie write-through) and your controller does write-through caching and you leave fsync=on and full_page_writes=on which is the default then you shouldn't have any data integrity issues. Note that many drives, especially IDE drives ship with write caching enabled (ie, write-back). And without a BBU many people are tempted to set fsync=off which improves performance at the cost of data loss on a system crash or power failure. With a BBU there's no advantage to fsync=off so that temptation to risk data loss is removed. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com
Gregory Stark wrote: >> From the DELL site it seems this `PERC 5/i' on board controller >> (assuming that's what you have) doesn't even have a BBU. If you don't >> plan to post here in a few weeks again about data corruption, go out and >> shop a serious controller. > > This is a bit of a strange comment. A BBU will improve performance but > Postgres doesn't require one to guarantee data integrity. > > If your drives have write caching disabled (ie write-through) and your > controller does write-through caching and you leave fsync=on and > full_page_writes=on which is the default then you shouldn't have any data > integrity issues. That was my point, controllers without BBU usually leave drive caches turned on, as with drive caches off performance would be unbearable bad. -- Best regards, Hannes Dorbath
On Sat, Jul 14, 2007 at 12:19:51PM +0200, Hannes Dorbath wrote: > Gregory Stark wrote: > >> From the DELL site it seems this `PERC 5/i' on board controller > >> (assuming that's what you have) doesn't even have a BBU. If you don't > >> plan to post here in a few weeks again about data corruption, go out and > >> shop a serious controller. > > > > This is a bit of a strange comment. A BBU will improve performance but > > Postgres doesn't require one to guarantee data integrity. > > > > If your drives have write caching disabled (ie write-through) and your > > controller does write-through caching and you leave fsync=on and > > full_page_writes=on which is the default then you shouldn't have any data > > integrity issues. > > That was my point, controllers without BBU usually leave drive caches > turned on, as with drive caches off performance would be unbearable bad. Wow, are you sure about that? I've never heard it before, but that'd be pretty disturbing if it's true... -- Jim Nasby decibel@decibel.org EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)