Thread: recommended way of separating data from indexes
Hi, I looked for quite a while but must have been looking in the wrong place... I have a 6 disk (x146GB) system running Centos 5.1 - RAID 1 (2 disks) and RAID 1+0 (4 disks). This seemed to be the recommended way of doing it but I may have been looking in the wrong place. The system is replicated using log shipping, so we have the archive command activated. What are the recommendations for this kind of system? The system is on the RAID 1 disk. My idea was to separate only the data onto the RAID 1+0 and leave the logs and archive and rest on the RAID 1. Is this the way to go? What is the recommended way of doing this? Just using symbolic links? Help! Cheers Anton -- echo '16i[q]sa[ln0=aln100%Pln100/snlbx]sbA0D4D465452snlbxq' | dc This will help you for 99.9% of your problems ...
Anton Melser wrote: > Hi, > I looked for quite a while but must have been looking in the wrong place... > I have a 6 disk (x146GB) system running Centos 5.1 - RAID 1 (2 disks) > and RAID 1+0 (4 disks). This seemed to be the recommended way of doing > it but I may have been looking in the wrong place. The system is > replicated using log shipping, so we have the archive command > activated. > What are the recommendations for this kind of system? That's going to depend on your disk activity, which will depend on usage patterns. > The system is on > the RAID 1 disk. My idea was to separate only the data onto the RAID > 1+0 and leave the logs and archive and rest on the RAID 1. Is this the > way to go? What is the recommended way of doing this? Just using > symbolic links? Help! Read the tablespaces chapter of the manuals. If you've got a fair amount of writing then you'll want to make sure the WAL can be written to as quickly as possibly. If you've got other write activity occurring on your system disks (e.g. lots of system-log activity, mailserver etc) then that's probably not the best place for the WAL. On the other hand, database reads+writes will interfere if you put everything on the RAID 10. So - it will depend. -- Richard Huxton Archonet Ltd
Hi, >> I have a 6 disk (x146GB) system running Centos 5.1 - RAID 1 (2 disks) >> and RAID 1+0 (4 disks). This seemed to be the recommended way of doing >> it but I may have been looking in the wrong place. The system is >> replicated using log shipping, so we have the archive command >> activated. >> What are the recommendations for this kind of system? > > That's going to depend on your disk activity, which will depend on usage > patterns. It's a website, with probably around 98% read to 2% write, and the writes only to a few tables. >> The system is on >> >> the RAID 1 disk. My idea was to separate only the data onto the RAID >> 1+0 and leave the logs and archive and rest on the RAID 1. Is this the >> way to go? What is the recommended way of doing this? Just using >> symbolic links? Help! > > Read the tablespaces chapter of the manuals. > > If you've got a fair amount of writing then you'll want to make sure the WAL > can be written to as quickly as possibly. If you've got other write activity > occurring on your system disks (e.g. lots of system-log activity, mailserver > etc) then that's probably not the best place for the WAL. On the other hand, > database reads+writes will interfere if you put everything on the RAID 10. > > So - it will depend. The machine is only doing this one DB, with the odd email being sent by postfix (20 p/d, so nothing) and for the moment we aren't doing any real logging apart from postgres internal (so not even activity logs or query logs, etc). So given that disk usage is pretty much 100% pgsql, and it's mainly read, does my architecture stand up? And thanks, I'll have a read of the tablespaces chapter - I looked pretty much everywhere but there! Cheers Anton
Anton Melser wrote: > > It's a website, with probably around 98% read to 2% write, and the > writes only to a few tables. > The machine is only doing this one DB, with the odd email being sent > by postfix (20 p/d, so nothing) and for the moment we aren't doing any > real logging apart from postgres internal (so not even activity logs > or query logs, etc). > > So given that disk usage is pretty much 100% pgsql, and it's mainly > read, does my architecture stand up? And thanks, I'll have a read of > the tablespaces chapter - I looked pretty much everywhere but there! With a small number of writes, it probably doesn't matter too much. If you symlink the PGDATA directory, or have it in a mount you can move then you can always change your mind later. -- Richard Huxton Archonet Ltd