Обсуждение: PostgreSQL over NFS?
I've been using PostgreSQL for a few years now in various projects, and I've been very happy with its features and performance. I have a client who wants to know how PostgreSQL (7) will perform over NFS. The NFS client is Solaris, the server is a big network storage appliance. The network is probably gigabit ethernet. My first reaction is to tell them they're just crazy, and that's not how a database is intended to work, and they should buy some fast, redundant local storage. I thought I'd ask the designers and users here so I could back up my recommendations. -- Shaw Terwilliger <sterwill@sourcegear.com> SourceGear Corporation 217.356.0105 x 641
Вложения
-- Start of PGP signed section. > I've been using PostgreSQL for a few years now in various projects, and > I've been very happy with its features and performance. > > I have a client who wants to know how PostgreSQL (7) will perform over > NFS. The NFS client is Solaris, the server is a big network storage > appliance. The network is probably gigabit ethernet. > > My first reaction is to tell them they're just crazy, and that's not how > a database is intended to work, and they should buy some fast, redundant > local storage. I thought I'd ask the designers and users here so I could > back up my recommendations. It is not performance I would be concerned about, but reliability. NFS has no state for reliability. I have to ask why they are using NFS rather than putting it on a drive local to the machine. If they say they want to share the data between two machines, that is even crazier. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026
* Shaw Terwilliger <sterwill@sourcegear.com> [010209 15:12] wrote: > I've been using PostgreSQL for a few years now in various projects, and > I've been very happy with its features and performance. > > I have a client who wants to know how PostgreSQL (7) will perform over > NFS. The NFS client is Solaris, the server is a big network storage > appliance. The network is probably gigabit ethernet. > > My first reaction is to tell them they're just crazy, and that's not how > a database is intended to work, and they should buy some fast, redundant > local storage. I thought I'd ask the designers and users here so I could > back up my recommendations. NFS == Not F****** Stable, don't do it. :) Any DBA will want to hurt you when he hears about you running a production DB over NFS. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk."
Shaw Terwilliger <sterwill@sourcegear.com> writes:
> I have a client who wants to know how PostgreSQL (7) will perform over
> NFS. The NFS client is Solaris, the server is a big network storage=20
> appliance. The network is probably gigabit ethernet.
> My first reaction is to tell them they're just crazy,
I agree.
Aside from the speed issues, there's a serious reliability problem;
AFAIR, NFS doesn't guarantee very much about write ordering, which
means a crash could leave you with corrupt data.
Seems a lot better to run the Postgres server on the machine where
the storage is.
regards, tom lane
> It is not performance I would be concerned about, but reliability. NFS > has no state for reliability. I have to ask why they are using NFS > rather than putting it on a drive local to the machine. If they say > they want to share the data between two machines, that is even crazier. They may want to put the data on a file server, so that it gets backed up, and has the advantage of a hardware fault-tolerant RAID array. Tht has it's merits, but I don't think it woul dbe that great for performance. We spent the money to put another RAID array in the database machine, both for reliability and speed. Once per night, the DB is dumped, and the dump is copied to the file server, so that we have a second copy somewhere, and it's included in the nightly tape backup. steve
* Tom Lane <tgl@sss.pgh.pa.us> [010209 15:40] wrote: > Shaw Terwilliger <sterwill@sourcegear.com> writes: > > I have a client who wants to know how PostgreSQL (7) will perform over > > NFS. The NFS client is Solaris, the server is a big network storage=20 > > appliance. The network is probably gigabit ethernet. > > > My first reaction is to tell them they're just crazy, > > I agree. > > Aside from the speed issues, there's a serious reliability problem; > AFAIR, NFS doesn't guarantee very much about write ordering, which > means a crash could leave you with corrupt data. Actually NFS has very strong write ordering semantics, it just has terrible cache coherency. Meaning two machines accessing the same file will most likely see different things if the file is updated moderately. For NFSv2 _all_ writes must be done syncronously. For NFSv3 there's a seperate commit RPC that needs to succeed before the local machine returns from fsync. There's also the issue that NFS requests are done async, meaning that you won't get an error on write(2)/read(2) until close(2) I'm not even sure if fsync(2) can or will return an error on an NFS error, this can be disasterous for a database. You can get around that by not running any async nfs kernel threads on the client (nfsiod under *BSD) however your performance will go to pot if you disable the async NFS subsystem. Even then there's probably more black magic that can cause wierd things to happen. > Seems a lot better to run the Postgres server on the machine where > the storage is. Agreed. :) -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk."
Bruce Momjian wrote: > It is not performance I would be concerned about, but reliability. NFS > has no state for reliability. I have to ask why they are using NFS > rather than putting it on a drive local to the machine. If they say > they want to share the data between two machines, that is even crazier. I did search through the archives, and saw the reliability thing mentioned (no state means locks aren't gone when the database server dies). Nothing has been deployed yet, and I'm pretty sure I can convince them to go for local disks (this is a large deployment, and they've got the budget for the system). -- Shaw Terwilliger <sterwill@sourcegear.com> SourceGear Corporation 217.356.0105 x 641
Вложения
Alfred Perlstein wrote: > NFS == Not F****** Stable, don't do it. :) Any DBA will want to > hurt you when he hears about you running a production DB over NFS. Well, I thought it wasn't a very safe thing to do. Their network administrator (the guy who buys machines, schedules backups, etc.) suggested looking into NFS storage. I think he just wanted to keep his backup/restore plans simple (do it all on the network applicance) and doesn't realize how a database server reads and writes to disks, and NFS gets in the way. -- Shaw Terwilliger <sterwill@sourcegear.com> SourceGear Corporation 217.356.0105 x 641
Вложения
Alfred Perlstein wrote: > Actually NFS has very strong write ordering semantics, it just has > terrible cache coherency. Meaning two machines accessing the same > file will most likely see different things if the file is updated > moderately. I'm not an NFS guru by any means, but I've noticed episodes of cache incoherency from NFS-mounted home directories on two workstations. Running two postgresql database servers on two hosts accessing the same data space through NFS sounds like asking for corruption, and was, luckily, never suggested. -- Shaw Terwilliger <sterwill@sourcegear.com> SourceGear Corporation 217.356.0105 x 641
Вложения
On Fri, 9 Feb 2001, Shaw Terwilliger wrote: > I've been using PostgreSQL for a few years now in various projects, and > I've been very happy with its features and performance. > > I have a client who wants to know how PostgreSQL (7) will perform over > NFS. The NFS client is Solaris, the server is a big network storage > appliance. The network is probably gigabit ethernet. > > My first reaction is to tell them they're just crazy, and that's not how > a database is intended to work, and they should buy some fast, redundant > local storage. I thought I'd ask the designers and users here so I could > back up my recommendations. we use mysql over nfs here. it works fine. the nfs server is a netapp. it's mounted over a gigabit ethernet crossover cable to the linux machine that runs mysqld. it's unlikely that gigabit ethernet would be much of a bottleneck on any modern disks, plus netapp's wafl filesystem is basically faster than anything out there right now, so the only overhead is the tcp/ip (udp) layer, which probably isn't that expensive. running it over a 100megabit line would probably slow things down some, but it all depends on how hard you're going to be pushing it. so the issue left is reliability. i've looked over some of the replies already that talk about unreliability in general, async issues, and locking issues. here's what you do to avoid all of that: use an nfs implementation that works. we use linux 2.2.18 with mount and nfs-utils packages from http://nfs.sourceforge.net/. we use nfsv3, not v2, and we mount the filesystem with the sync option. problem solved. i haven't tried this with postgresql, but we actually are planning on switching to postgresql down the road, so hopefully it'll be ok. heh. -tcl.
On Fri, 9 Feb 2001, tc lewis wrote: > > On Fri, 9 Feb 2001, Shaw Terwilliger wrote: > > I've been using PostgreSQL for a few years now in various projects, and > > I've been very happy with its features and performance. > > > > I have a client who wants to know how PostgreSQL (7) will perform over > > NFS. The NFS client is Solaris, the server is a big network storage > > appliance. The network is probably gigabit ethernet. > > > > My first reaction is to tell them they're just crazy, and that's not how > > a database is intended to work, and they should buy some fast, redundant > > local storage. I thought I'd ask the designers and users here so I could > > back up my recommendations. > > we use mysql over nfs here. it works fine. the nfs server is a netapp. > it's mounted over a gigabit ethernet crossover cable to the linux machine > that runs mysqld. it's unlikely that gigabit ethernet would be much of a > bottleneck on any modern disks, plus netapp's wafl filesystem is basically > faster than anything out there right now, so the only overhead is the > tcp/ip (udp) layer, which probably isn't that expensive. running it over > a 100megabit line would probably slow things down some, but it all depends > on how hard you're going to be pushing it. > > so the issue left is reliability. i've looked over some of the replies > already that talk about unreliability in general, async issues, and > locking issues. here's what you do to avoid all of that: use an nfs > implementation that works. we use linux 2.2.18 with mount and nfs-utils > packages from http://nfs.sourceforge.net/. we use nfsv3, not v2, and we > mount the filesystem with the sync option. problem solved. > > i haven't tried this with postgresql, but we actually are planning on > switching to postgresql down the road, so hopefully it'll be ok. heh. > oh, and of course, we only mount the data files on _one_ client. we do _not_ run 2 mysqlds on the same data. that would probably be very bad with mysql or postgresql. -tcl.
Steve Wolfe wrote: > They may want to put the data on a file server, so that it gets backed up, > and has the advantage of a hardware fault-tolerant RAID array. Tht has it's > merits, but I don't think it woul dbe that great for performance. We spent > the money to put another RAID array in the database machine, both for > reliability and speed. Once per night, the DB is dumped, and the dump is > copied to the file server, so that we have a second copy somewhere, and it's > included in the nightly tape backup. The feeling I got from speaking with their administrator was that they wanted what you mentioned: easy backups on the applicance with the automatic tape robot. In my application, if the PostgreSQL host goes down, all customers have no service. Assuming RAID on the database server host, and plenty of RAM and CPU cycles, they CPUs could still explode, or a meteorite could find its way into the power supply (supplies?). It will probably be necessary to have a backup host on hand (assume identical hardware). Database connections to other system components do not need to be maintained (they are pooled by a local process running on the database server which speaks stateless things to other components). If this host could run PostgreSQL out of the production environment, but obtain periodic updates (once or twice daily would probably be fine), it could be configured to assume the first host's IP address in case of failure, and the system will chug along nicely. Besides dumping and COPY'ing the data into the second server, is there another form of easy one-way replication available? My schema has just a few simple tables (six tables, a few rows each). But these tables may hold a few million records each. I've estimated the total data size to be somewhere around 10 GB (with WAGs for index sizes) for 5 million users. I guess COPY would work. -- Shaw Terwilliger <sterwill@sourcegear.com> SourceGear Corporation 217.356.0105 x 641
Вложения
* Shaw Terwilliger <sterwill@sourcegear.com> [010209 16:18] wrote: > Alfred Perlstein wrote: > > Actually NFS has very strong write ordering semantics, it just has > > terrible cache coherency. Meaning two machines accessing the same > > file will most likely see different things if the file is updated > > moderately. > > I'm not an NFS guru by any means, but I've noticed episodes of cache > incoherency from NFS-mounted home directories on two workstations. > Running two postgresql database servers on two hosts accessing the > same data space through NFS sounds like asking for corruption, and > was, luckily, never suggested. My statement is also incorrect, NFS has loose write ordering semantics, but it does have strong reliability, meaning that fsync(2)/close(2) must sync all data to backing NFS server or return an error. The part about cache incoherency is very true, the _only_ cache coherency NFS offers is _only_ in the v3 spec, and is specifically called 'wcc' 'weak cache coherency' (afaik). So yes, you can expect differnent NFS clients to get different inconsistant views on heavily modified files unless they use advisory locking (which should fsync out locked ranges before release). Anyhow, if the idea is just to get a nice backup system, you could do a pg_dump and write the output to a NFS mounted FS, there's probably less that can go wrong with a large sequencial write than heavy shared read/write/seek. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk."
I've heard of other people running databases on a Netapp Filer I think this is generally ok because the netapp has a special write cache in NVram and that's what makes it so fast. On Fri, 9 Feb 2001, tc lewis wrote: > > On Fri, 9 Feb 2001, Shaw Terwilliger wrote: > > I've been using PostgreSQL for a few years now in various projects, and > > I've been very happy with its features and performance. > > > > I have a client who wants to know how PostgreSQL (7) will perform over > > NFS. The NFS client is Solaris, the server is a big network storage > > appliance. The network is probably gigabit ethernet. > > > > My first reaction is to tell them they're just crazy, and that's not how > > a database is intended to work, and they should buy some fast, redundant > > local storage. I thought I'd ask the designers and users here so I could > > back up my recommendations. > > we use mysql over nfs here. it works fine. the nfs server is a netapp. > it's mounted over a gigabit ethernet crossover cable to the linux machine > that runs mysqld. it's unlikely that gigabit ethernet would be much of a > bottleneck on any modern disks, plus netapp's wafl filesystem is basically > faster than anything out there right now, so the only overhead is the > tcp/ip (udp) layer, which probably isn't that expensive. running it over > a 100megabit line would probably slow things down some, but it all depends > on how hard you're going to be pushing it. > > so the issue left is reliability. i've looked over some of the replies > already that talk about unreliability in general, async issues, and > locking issues. here's what you do to avoid all of that: use an nfs > implementation that works. we use linux 2.2.18 with mount and nfs-utils > packages from http://nfs.sourceforge.net/. we use nfsv3, not v2, and we > mount the filesystem with the sync option. problem solved. > > i haven't tried this with postgresql, but we actually are planning on > switching to postgresql down the road, so hopefully it'll be ok. heh. > > -tcl. >
Shaw Terwilliger wrote: > Besides dumping and COPY'ing the data into the second server, is there > another form of easy one-way replication available? My schema has just > a few simple tables (six tables, a few rows each). But these tables > may hold a few million records each. I've estimated the total data size > to be somewhere around 10 GB (with WAGs for index sizes) for 5 million > users. I guess COPY would work. Oops... up there, I meant to say my tables had a few columns each, not rows. A few tables may hold a few million records. One big users table holds an int id and a few TEXT fields, the other tables use keys into the users table's id field and may store some strings. -- Shaw Terwilliger <sterwill@sourcegear.com> SourceGear Corporation 217.356.0105 x 641
Вложения
On Fri, 9 Feb 2001, adb wrote: > I've heard of other people running databases on a Netapp Filer > I think this is generally ok because the netapp has a special > write cache in NVram and that's what makes it so fast. > yeah, basically a write returns almost instantaneously (or much closer than comparative to your normal machine writing to disk at least) with a netapp filer. they're very fast. and also very expensive. -tcl.
> The part about cache incoherency is very true, the _only_ cache coherency > NFS offers is _only_ in the v3 spec, and is specifically called 'wcc' > 'weak cache coherency' (afaik). So yes, you can expect differnent > NFS clients to get different inconsistant views on heavily modified > files unless they use advisory locking (which should fsync out locked > ranges before release). > > Anyhow, if the idea is just to get a nice backup system, you could > do a pg_dump and write the output to a NFS mounted FS, there's probably > less that can go wrong with a large sequencial write than heavy shared > read/write/seek. Or just rsh over to the database system and pipe the output back to the 'backup' machine. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026
* adb <adb@Beast.COM> [010209 16:41] wrote: > I've heard of other people running databases on a Netapp Filer > I think this is generally ok because the netapp has a special > write cache in NVram and that's what makes it so fast. That can't help bugs in the NFS server or client code that can cause weird stuff to happen (crashes, corruption, outtages). -Alfred
On Fri, Feb 09, 2001 at 04:23:10PM -0800, Alfred Perlstein wrote:
> Anyhow, if the idea is just to get a nice backup system, you could
> do a pg_dump and write the output to a NFS mounted FS, there's probably
> less that can go wrong with a large sequencial write than heavy shared
> read/write/seek.
Still new to this but....
Can pg_dump be piped through gzip et al? Use a few cpu strokes to save
network bandwidth may be beneficial.
mrc
--
Mike Castle Life is like a clock: You can work constantly
dalgoda@ix.netcom.com and be right all the time, or not work at all
www.netcom.com/~dalgoda/ and be right at least twice a day. -- mrc
We are all of us living in the shadow of Manhattan. -- Watchmen
On Fri, Feb 09, 2001 at 07:42:12PM -0500, Bruce Momjian wrote:
> Or just rsh over to the database system and pipe the output back to the
> 'backup' machine.
Can one even log into a netapp to do this kind of things? I always thought
they were pretty much a black box file server, but I've never played with
one.
mrc
--
Mike Castle Life is like a clock: You can work constantly
dalgoda@ix.netcom.com and be right all the time, or not work at all
www.netcom.com/~dalgoda/ and be right at least twice a day. -- mrc
We are all of us living in the shadow of Manhattan. -- Watchmen
* tc lewis <tcl@bunzy.net> [010209 16:47] wrote: > > On Fri, 9 Feb 2001, adb wrote: > > I've heard of other people running databases on a Netapp Filer > > I think this is generally ok because the netapp has a special > > write cache in NVram and that's what makes it so fast. > > > > yeah, basically a write returns almost instantaneously (or much closer > than comparative to your normal machine writing to disk at least) with a > netapp filer. they're very fast. and also very expensive. You can also get a raid with battery backup, this would achieve pretty much the same thing. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk."
* Mike Castle <dalgoda@ix.netcom.com> [010209 16:57] wrote: > On Fri, Feb 09, 2001 at 04:23:10PM -0800, Alfred Perlstein wrote: > > Anyhow, if the idea is just to get a nice backup system, you could > > do a pg_dump and write the output to a NFS mounted FS, there's probably > > less that can go wrong with a large sequencial write than heavy shared > > read/write/seek. > > Still new to this but.... > > Can pg_dump be piped through gzip et al? Use a few cpu strokes to save > network bandwidth may be beneficial. Yes it can. It's a cpu/space/network tradeoff, if you use low compression you might do pretty well, saving CPU and at the same time getting pretty good compression on plain-text. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk."
On Fri, 9 Feb 2001, Alfred Perlstein wrote: > * tc lewis <tcl@bunzy.net> [010209 16:47] wrote: > > > > On Fri, 9 Feb 2001, adb wrote: > > > I've heard of other people running databases on a Netapp Filer > > > I think this is generally ok because the netapp has a special > > > write cache in NVram and that's what makes it so fast. > > > > > > > yeah, basically a write returns almost instantaneously (or much closer > > than comparative to your normal machine writing to disk at least) with a > > netapp filer. they're very fast. and also very expensive. > > You can also get a raid with battery backup, this would achieve > pretty much the same thing. > how's that? storage arrays will require you to use a filesystem that your operating system supports. or do some storage array companies provide their own filesystems and drivers for misc systems? same thing i guess. -tcl.
> > > > how's that? storage arrays will require you to use a filesystem that your > > operating system supports. or do some storage array companies provide > > their own filesystems and drivers for misc systems? same thing i guess. > > It has a persistant write cache, meaning it can ACK a write as being > sync'd to disk even if it's only been copied into the RAID's memory > cache (because it's persistant). Same thing that netapp does. > hmm, i suppose. i guess the filesystem wouldn't need to understand the logic of the underlying device. not sure. i don't think i've ever been presented with a storage array that does what you're saying (not saying they don't exist). -tcl.
* tc lewis <tcl@bunzy.net> [010209 17:02] wrote: > > > On Fri, 9 Feb 2001, Alfred Perlstein wrote: > > > * tc lewis <tcl@bunzy.net> [010209 16:47] wrote: > > > > > > On Fri, 9 Feb 2001, adb wrote: > > > > I've heard of other people running databases on a Netapp Filer > > > > I think this is generally ok because the netapp has a special > > > > write cache in NVram and that's what makes it so fast. > > > > > > > > > > yeah, basically a write returns almost instantaneously (or much closer > > > than comparative to your normal machine writing to disk at least) with a > > > netapp filer. they're very fast. and also very expensive. > > > > You can also get a raid with battery backup, this would achieve > > pretty much the same thing. > > > > how's that? storage arrays will require you to use a filesystem that your > operating system supports. or do some storage array companies provide > their own filesystems and drivers for misc systems? same thing i guess. It has a persistant write cache, meaning it can ACK a write as being sync'd to disk even if it's only been copied into the RAID's memory cache (because it's persistant). Same thing that netapp does. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk."
Has anyone tried the ODBC drivers with the beta? I'm just curious if the existing drivers will still work. --rob
* tc lewis <tcl@bunzy.net> [010209 17:08] wrote: > > > > > > > how's that? storage arrays will require you to use a filesystem that your > > > operating system supports. or do some storage array companies provide > > > their own filesystems and drivers for misc systems? same thing i guess. > > > > It has a persistant write cache, meaning it can ACK a write as being > > sync'd to disk even if it's only been copied into the RAID's memory > > cache (because it's persistant). Same thing that netapp does. > > > > hmm, i suppose. i guess the filesystem wouldn't need to understand the > logic of the underlying device. not sure. i don't think i've ever been > presented with a storage array that does what you're saying (not saying > they don't exist). All it does is present itself as a disk that super fast at writing as long as the cache doesn't fill up. I have an older card: amr0: <AMI MegaRAID> port 0x1080-0x10ff irq 18 at device 11.0 on pci0 amr0: firmware UF80 bios 1.61 128MB memory That has a slot for battery backup of the RAID cache. If the machine was to reboot, the raid would sync the cached data to disk sometime after coming back up. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk."
On Fri, Feb 09, 2001 at 08:08:10PM -0500, tc lewis wrote:
> hmm, i suppose. i guess the filesystem wouldn't need to understand the
> logic of the underlying device. not sure. i don't think i've ever been
> presented with a storage array that does what you're saying (not saying
> they don't exist).
At least Sun has had one for years.
But I think the Netapp would still out perform, NFS wise, a generic server
performing only NFS services. Just because of it's tweaked stuff,
including it's local file system.
I've heard of people running good sized Usenet farms against Netapp and
quite happy with the performance.
If it can keep usenet junkies happy, I would think that, performance wise,
it will do ok for database. I would think the client performance it more
critical in this case, than anything else.
Another point of concern is state of the system when a backup is taken.
Other threads pointed out the concern about backing up files during the
middle of transactions and the like. Better if able to ask the LVM layer
(or whatever) to take a snapshot, and then back THAT up. Does netapp offer
such facilities? (I would imagine so, but not positive). If not, one may
still have to do a pg_dump just to maintain stable backups.
mrc
--
Mike Castle Life is like a clock: You can work constantly
dalgoda@ix.netcom.com and be right all the time, or not work at all
www.netcom.com/~dalgoda/ and be right at least twice a day. -- mrc
We are all of us living in the shadow of Manhattan. -- Watchmen
Mike Castle <dalgoda@ix.netcom.com> writes: > Another point of concern is state of the system when a backup is taken. > Other threads pointed out the concern about backing up files during the > middle of transactions and the like. Better if able to ask the LVM layer > (or whatever) to take a snapshot, and then back THAT up. Does netapp offer > such facilities? (I would imagine so, but not positive). If not, one may > still have to do a pg_dump just to maintain stable backups. I don't think that LVM (or snapshots in general, which NetApps do indeed offer) will help without a way to tell PG to quiesce itself and flush all caches to disk. A random snapshot of a PG database will almost certainly not be consistent. I don't think PG has anything like Oracle's "hot backup" mode, except for pg_dump itself. -Doug
Shaw Terwilliger <sterwill@sourcegear.com> writes:
> Besides dumping and COPY'ing the data into the second server, is there
> another form of easy one-way replication available? My schema has just
Have you looked at PG's replication? It's included in 7.1, and you
can get it from (I think) www.postgresql.com for 7.0.
Chris
--
chris@mt.sri.com -----------------------------------------------------
Chris Jones SRI International, Inc.
www.sri.com
On Fri, Feb 09, 2001 at 04:58:51PM -0800, Alfred Perlstein wrote: > * Mike Castle <dalgoda@ix.netcom.com> [010209 16:57] wrote: > > On Fri, Feb 09, 2001 at 04:23:10PM -0800, Alfred Perlstein wrote: > > > Anyhow, if the idea is just to get a nice backup system, you could > > > do a pg_dump and write the output to a NFS mounted FS, there's probably > > > less that can go wrong with a large sequencial write than heavy shared > > > read/write/seek. > > > > Still new to this but.... > > > > Can pg_dump be piped through gzip et al? Use a few cpu strokes to save > > network bandwidth may be beneficial. > > Yes it can. It's a cpu/space/network tradeoff, if you use low > compression you might do pretty well, saving CPU and at the same > time getting pretty good compression on plain-text. I regularily use sth. like /usr/bin/pg_dump dbname | ssh -C other.host /usr/bin/pgsql dbname for this, "-C" tells ssh to compress data on-the-fly *and* your connection is encrypted, allowing for doing this to a remote machine securely. Installing your public key (identity.pub) on the target-computer in ~/.ssh/knownhosts will allow to get this running without a login dialog. You may set your account-name on other.host together with enforced compression and higher (or lower compression-levels) with an entry for other.host in ~/.ssh/config on the source-host (well, man ssh ;-)). E.g.: Host other.host Compression yes CompressionLevel 9 (1-9 available, 6 beeing default) User zeibigm ForwardX11 no ssh uses an gzip-agorithm for this. Best Regards Mirko -- mirko@picard.inka.de http://sites.inka.de/picard/