Thread: databases and RAID ...
Hi I am setting up a new database server. the data is critical that is why i am thniking to mirror the SCSI disks in RAID 1 configuration. I do not have a hardware raid controller. could anyone give me some pointer , or suggest me if its advisable to use RAID 1 with database servers. thanks regds mallah. -- Rajesh Kumar Mallah, Project Manager (Development) Infocom Network Limited, New Delhi phone: +91(11)6152172 (221) (L) ,9811255597 (M) Visit http://www.trade-india.com , India's Leading B2B eMarketplace.
Rajesh Kumar Mallah. wrote: > Hi > > I am setting up a new database server. > the data is critical that is why i am thniking > to mirror the SCSI disks in RAID 1 configuration. > > I do not have a hardware raid controller. > > could anyone give me some pointer , or suggest me > if its advisable to use RAID 1 with database servers. We use a RAID1 here and it works just fine. We have a RAID card, though...that helps a lot. --Jeremy
"Rajesh Kumar Mallah." wrote: > I am setting up a new database server. > the data is critical that is why i am thniking > to mirror the SCSI disks in RAID 1 configuration. > I do not have a hardware raid controller. If it's that critical, you would be wise to go buy a hardware RAID controller. > could anyone give me some pointer , or suggest me > if its advisable to use RAID 1 with database servers. Probably not a bad idea, with hardware; the controller should be able to stream the data across both disks without slowing down writes. Software-based RAID may show slower performance as it must process the command streams for *both* disks in the OS instead of offloading that task to the controller... although if the disks are SCSI with a decent SCSI card that should be minimal. Note that if you're looking for a system you can hotswap, you will probably need to go SCSI in any case; I'm not aware of any hotswap-capable IDE RAID systems. -kgd -- Money is overrated.
I would use hardware RAID level 1 for performance reasons. Egon "Rajesh Kumar Mallah." wrote: > Hi > > I am setting up a new database server. > the data is critical that is why i am thniking > to mirror the SCSI disks in RAID 1 configuration. > > I do not have a hardware raid controller. > > could anyone give me some pointer , or suggest me > if its advisable to use RAID 1 with database servers. > > thanks > > regds > mallah. > > -- > Rajesh Kumar Mallah, > Project Manager (Development) > Infocom Network Limited, New Delhi > phone: +91(11)6152172 (221) (L) ,9811255597 (M) > > Visit http://www.trade-india.com , > India's Leading B2B eMarketplace. > > ---------------------------(end of broadcast)--------------------------- > TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org
Good Morning Mallah, I've heard bad things from a friend that worked at IBM about using RAID and databases. He said there could be a definite performance hit with a hardware raid controller doing RAID5, so i can only imagine that software raid would be worse :(. Mirroring should be as bad, but i would definitly look into a hardware raid controller if you could. hope thishelps corey -----Original Message----- From: Rajesh Kumar Mallah. [SMTP:mallah@trade-india.com] Sent: Friday, May 24, 2002 5:55 AM To: pgsql-admin@postgresql.org Subject: [ADMIN] databases and RAID ... Hi I am setting up a new database server. the data is critical that is why i am thniking to mirror the SCSI disks in RAID 1 configuration. I do not have a hardware raid controller. could anyone give me some pointer , or suggest me if its advisable to use RAID 1 with database servers. thanks regds mallah. -- Rajesh Kumar Mallah, Project Manager (Development) Infocom Network Limited, New Delhi phone: +91(11)6152172 (221) (L) ,9811255597 (M) Visit http://www.trade-india.com , India's Leading B2B eMarketplace. ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org
use raid 10 (striping with mirroring) if you have more than 2 hard disks. much faster than raid 1. > Hi > > I am setting up a new database server. > the data is critical that is why i am thniking > to mirror the SCSI disks in RAID 1 configuration. > > I do not have a hardware raid controller. > > could anyone give me some pointer , or suggest me > if its advisable to use RAID 1 with database servers. > > > thanks > > > regds > mallah. > > > > > > > > > > -- > Rajesh Kumar Mallah, > Project Manager (Development) > Infocom Network Limited, New Delhi > phone: +91(11)6152172 (221) (L) ,9811255597 (M) > > Visit http://www.trade-india.com , > India's Leading B2B eMarketplace. > > > > ---------------------------(end of broadcast)--------------------------- > TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org
"Fred Moyer" <fred@digicamp.com>(by way of Rajesh Kumar Mallah. <mallah@trade-india.com>) writes:
> use raid 10 (striping with mirroring) if you have more than 2 hard
> disks. much faster than raid 1.
Is there any rhyme or reason to the various "RAID n" designations?
Or were they just invented on the spur of the moment?
feeling ignorant, tom lane
Hi Fred, I have only two hardisks and no HW card. how can i utilize them best? i do not want to loose data one fine day discovering one my SCSI havaing DB has failed. :-( should i run database on only 1 18GB scsi and pg_dump every 6 hrs my critical tables on other machine (which has not database and has 2*18GB SCSI in RAID 1) ? or should i go for SW RAID 1 configuration putting 2 hardrives in the DB server. ok , in worst case i will try both the configs and post the benchmarks ;-) thanks everyone for their time. regds mallah. On Saturday 25 May 2002 10:16 am, Fred Moyer wrote: > use raid 10 (striping with mirroring) if you have more than 2 hard > disks. much faster than raid 1. > > > Hi > > > > I am setting up a new database server. > > the data is critical that is why i am thniking > > to mirror the SCSI disks in RAID 1 configuration. > > > > I do not have a hardware raid controller. > > > > could anyone give me some pointer , or suggest me > > if its advisable to use RAID 1 with database servers. > > > > > > thanks > > > > > > regds > > mallah. > > > > > > > > > > > > > > > > > > > > -- > > Rajesh Kumar Mallah, > > Project Manager (Development) > > Infocom Network Limited, New Delhi > > phone: +91(11)6152172 (221) (L) ,9811255597 (M) > > > > Visit http://www.trade-india.com , > > India's Leading B2B eMarketplace. > > > > > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org > > ---------------------------(end of broadcast)--------------------------- > TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly -- Rajesh Kumar Mallah, Project Manager (Development) Infocom Network Limited, New Delhi phone: +91(11)6152172 (221) (L) ,9811255597 (M) Visit http://www.trade-india.com , India's Leading B2B eMarketplace.
On Fri, 2002-05-24 at 15:58, Kris Deugau wrote: > "Rajesh Kumar Mallah." wrote: > > I am setting up a new database server. > > the data is critical that is why i am thniking > > to mirror the SCSI disks in RAID 1 configuration. > > I do not have a hardware raid controller. > > If it's that critical, you would be wise to go buy a hardware RAID > controller. > > > could anyone give me some pointer , or suggest me > > if its advisable to use RAID 1 with database servers. > > Probably not a bad idea, with hardware; the controller should be able > to stream the data across both disks without slowing down writes. > Software-based RAID may show slower performance as it must process the > command streams for *both* disks in the OS instead of offloading that > task to the controller... although if the disks are SCSI with a decent > SCSI card that should be minimal. > > Note that if you're looking for a system you can hotswap, you will > probably need to go SCSI in any case; I'm not aware of any > hotswap-capable IDE RAID systems. 3ware escalade series. IDE. hot-swap, Drivers in recent linux kernels.
If I was in your situation I would put both 18's into a sw raid 1 configuration. You may lose some speed on the writes since it's doing more work than writing to 1 disk but the redundancy will be well worth it should the day come when you need it. -----Original Message----- From: pgsql-admin-owner@postgresql.org [mailto:pgsql-admin-owner@postgresql.org]On Behalf Of Rajesh Kumar Mallah. Sent: Friday, May 24, 2002 10:15 PM To: pgsql-admin Subject: Re: [ADMIN] databases and RAID ... Hi Fred, I have only two hardisks and no HW card. how can i utilize them best? i do not want to loose data one fine day discovering one my SCSI havaing DB has failed. :-( should i run database on only 1 18GB scsi and pg_dump every 6 hrs my critical tables on other machine (which has not database and has 2*18GB SCSI in RAID 1) ? or should i go for SW RAID 1 configuration putting 2 hardrives in the DB server. ok , in worst case i will try both the configs and post the benchmarks ;-) thanks everyone for their time. regds mallah. On Saturday 25 May 2002 10:16 am, Fred Moyer wrote: > use raid 10 (striping with mirroring) if you have more than 2 hard > disks. much faster than raid 1. > > > Hi > > > > I am setting up a new database server. > > the data is critical that is why i am thniking > > to mirror the SCSI disks in RAID 1 configuration. > > > > I do not have a hardware raid controller. > > > > could anyone give me some pointer , or suggest me > > if its advisable to use RAID 1 with database servers. > > > > > > thanks > > > > > > regds > > mallah. > > > > > > > > > > > > > > > > > > > > -- > > Rajesh Kumar Mallah, > > Project Manager (Development) > > Infocom Network Limited, New Delhi > > phone: +91(11)6152172 (221) (L) ,9811255597 (M) > > > > Visit http://www.trade-india.com , > > India's Leading B2B eMarketplace. > > > > > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org > > ---------------------------(end of broadcast)--------------------------- > TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly -- Rajesh Kumar Mallah, Project Manager (Development) Infocom Network Limited, New Delhi phone: +91(11)6152172 (221) (L) ,9811255597 (M) Visit http://www.trade-india.com , India's Leading B2B eMarketplace. ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
Tom Lane writes: > Is there any rhyme or reason to the various "RAID n" designations? > Or were they just invented on the spur of the moment? The paper that introduced the term RAID used a numerical classification for the various schemes. (So I guess the answer is yes.) The traditional levels are: 0 Nonredundant 1 Mirrored 2 Memory-style ECC 3 Bit-interleaved parity 4 Block-interleaved parity 5 Block-interleaved distributed parity [Hennessy & Patterson] There are also other levels. One poster talked about RAID 10 which appears to be a mirrored RAID 5. -- Peter Eisentraut peter_e@gmx.net
On Sat, May 25, 2002 at 09:29:01PM +0200, Peter Eisentraut wrote: > 0 Nonredundant > 1 Mirrored > 2 Memory-style ECC > 3 Bit-interleaved parity > 4 Block-interleaved parity > 5 Block-interleaved distributed parity > [Hennessy & Patterson] > > There are also other levels. One poster talked about RAID 10 which > appears to be a mirrored RAID 5. No, RAID 10 is RAID 1 over RAID 0 (mirrored stripes). Mirrored RAID 5 would RAID 1 over RAID 5 or RAID 15 for short. -- Ragnar Kjorstad
<adding my $0.02>
JBOD : just a bunch of disks, not raid in my opinion
Raid 0 : striping over disks, no redundancy, hence the Redundancy in
Redundant Arrays of Independent Disks is zero.
Raid 1 : Mirroring, full redundancy, Redundancy 1(00%)
Raid 4: see thread
Raid 5: see thread,Striping across multiple disks with parity. You have
one spare drive, 3 drives minimum, recommend more cause raid-5 is SLOW
Raid 10: A mirrored pair of striped arrays (1+0).
from working with various raid controllers (ide and scsi) here is my
feedback (please rebuke me if needed as I'm sure others on this list have
more experience).
Performance (fastest->slowest)
hardware raid -> software raid
raid 0 -> 10 -> 1 -> 5
Redundancy (most -> least)
hardware raid -> software raid
10, 1 -> 5 -> 0
some people say raid 5 is the most redundant but if you have over seven
disks your change of two drives failing becomes a statistical reality, hence
raid 5 is best suited for arrays of 5-8 drives. RAID 10 and 1 are both
mirrored but can be expensive. raid 0 is the fastest but don't count put
mission critical data on it - add another n disks and make it raid 10.
IDE vs SCSI:
I have run both controllers and have found both perform well. The stripe
size for raid 10 and 0 is important - make it as large as possible for
databases (256k on scsi and 1 MB on ide) since you want the disk heads to
read as much as possible before seeking again. for databases use scsi if
you can - use ide for streaming audio/video. databases performance relies
on being fast at random reads/writes and that's where scsi wins.
> Is there any rhyme or reason to the various "RAID n" designations?
> Or were they just invented on the spur of the moment?
The paper that introduced the term RAID used a numerical classification
for the various schemes. (So I guess the answer is yes.) The traditional
levels are:
0 Nonredundant
1 Mirrored
2 Memory-style ECC
3 Bit-interleaved parity
4 Block-interleaved parity
5 Block-interleaved distributed parity
[Hennessy & Patterson]
There are also other levels. One poster talked about RAID 10 which
appears to be a mirrored RAID 5.
--
Peter Eisentraut peter_e@gmx.net
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On Fri, 24 May 2002, Rajesh Kumar Mallah. wrote: > I am setting up a new database server. > the data is critical that is why i am thniking > to mirror the SCSI disks in RAID 1 configuration. > I do not have a hardware raid controller. > could anyone give me some pointer , or suggest me > if its advisable to use RAID 1 with database servers. Hi Mallah. Sorry I'm so delayed in responding to this. Before you consider raid because the data is critical, I'd suggest you come up with a disaster recovery scenario first. Raid is good, but it's a false sense of security. Raid is meant to protect media failures, and only media failures. There are many other types of failures that you should consider before media failures. Sorry to preach, but I do this as a day job so I can't help it sometimes... Software raid will slow down performance, but if performance isn't a problem, then it's OK. I use NetBSD which has a program called raidframe that apparently works pretty well. I haven't had time to set it up yet. FreeBSD uses vinum, and Linux has a new volume management system that looks pretty slick as well. I don't remember what it's called. If performance is an issue, buy a hardware raid controller, and use scsi. It's expensive, but so is data. Andy -- acruhl@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org
On Sat, May 25, 2002 at 12:45:12PM -0700, Fred Moyer wrote: > Performance (fastest->slowest) > hardware raid -> software raid > raid 0 -> 10 -> 1 -> 5 > Redundancy (most -> least) > hardware raid -> software raid > 10, 1 -> 5 -> 0 It's really not possible to compare RAID-levels independent from what the system is beeing used for. E.g. lots of seeks vs continous access, read-intensive vs write-intensive, how many simultanious accesses and so on. E.g. RAID 1 / 10 can easily be as fast, or faster than RAID 0 for read intensive work. RAID 5 has a very high penality when doing small writes, but the effect can be reduced by good RAID-controllers with lots of battery-backed cached. For a typical database-application I would agree with your statement except that RAID 1 is probably faster than RAID 10. -- Ragnar Kjorstad Big Storage
Peter Eisentraut wrote: >Tom Lane writes: > > > >>Is there any rhyme or reason to the various "RAID n" designations? >>Or were they just invented on the spur of the moment? >> >> > >The paper that introduced the term RAID used a numerical classification >for the various schemes. (So I guess the answer is yes.) The traditional >levels are: > >0 Nonredundant >1 Mirrored >2 Memory-style ECC >3 Bit-interleaved parity >4 Block-interleaved parity >5 Block-interleaved distributed parity >[Hennessy & Patterson] > >There are also other levels. One poster talked about RAID 10 which >appears to be a mirrored RAID 5. > > > No Raid 10 is Raid 1 + 0 its strong points are faster writes but slower reads. - Bill
On Sun, May 26, 2002 at 08:00:50AM -0700, Bill Cunningham wrote: > No Raid 10 is Raid 1 + 0 its strong points are faster writes but slower > reads. RAID 10 reads will actually be faster than RAID 5, but it will require more disks. (2n instead of n+1). -- Ragnar Kjorstad Big Storage
Peter Eisentraut <peter_e@gmx.net> writes: > There are also other levels. One poster talked about RAID 10 which > appears to be a mirrored RAID 5. Those are multi-level RAID systems: - RAID (0+1) RAID 1 (high availability) plus RAID 0 (enhaced I/O performace through striping). - RAID (3+0) A logical volume with several RAID 3 logical member drives. -RAID (5+0) A logical volume with several RAID 3 logical member drives. -RAID (5+1) Requires multiple RAID controllers. Each layer-1 RAID controller handles one RAID 5 logical drive and layer-2 RAID controller performs RAID 1 (mirroring) function to the virtual disks controlled by all of the layer-1 RAID controllers. - RAID (5+5) Requires multiple RAID controllers. Each layer-1 RAID controller handles one to several RAID 5 logical drives and layer-2 RAID controller performs RAID 5 to the virtual disks controlled by all of the layer-1 RAID controllers. - RAID 10 Logical volume with RAID 1 logical drives; stripping plus mirroring. - RAID 30 Logical volume with RAID 3 logical drives; RAID 3 plus striping. - RAID 50 Logical volume with RAID 5 logical drives; RAID 3 plus striping. All about RAID: "The RAID book" from the RAID Advisory Board. Regards, Manuel.
> On Sun, May 26, 2002 at 08:00:50AM -0700, Bill Cunningham wrote: > > No Raid 10 is Raid 1 + 0 its strong points are faster writes but slower > > reads. > > RAID 10 reads will actually be faster than RAID 5, but it will require > more disks. (2n instead of n+1). There also seems to be a combination of RAID 5 + 0, called RAID 50. It performs faster than RAID 5, and slower than RAID 10. Disk usage is also between those two (n+2). Sander.
On Fri, 24 May 2002, Kris Deugau wrote: [snip] KD> Note that if you're looking for a system you can hotswap, you will KD> probably need to go SCSI in any case; I'm not aware of any KD> hotswap-capable IDE RAID systems. Not exactly ;-) Promise TX2 and TX4 with special enclosures do the trick. If you need to scale further, 3Ware Escalade controllers (www.3ware.com) would be the right choice. Sincerely, D.Marck [DM5020, DM268-RIPE, DM3-RIPN] ------------------------------------------------------------------------ *** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru *** ------------------------------------------------------------------------
At 01:31 PM 5/26/02 , Manuel Sugawara wrote:
>-RAID (5+0) A logical volume with several RAID 3 logical member
>drives.
Perhaps a typo?
We built what we called a "plaid", in which we built RAID 5 arrays on Sun
A3500 (hardware RAID with cache) [think horizontal] and then striped across
the RAID LUNs with Veritas Volume Manager [think vertical]. The intent was
to have redundance =and= keep essentially all spindles involved in each I/O
(for performance).
This was to hold an Informix database, and we set the stripe size to match
a database page size.
-crl
--
Chad R. Larson (CRL22) chad@eldocomp.com
Eldorado Computing, Inc. 602-604-3100
5353 North 16th Street, Suite 400
Phoenix, Arizona 85016-3228
"Chad R. Larson" <clarson@eldocomp.com> writes: > At 01:31 PM 5/26/02 , Manuel Sugawara wrote: > >-RAID (5+0) A logical volume with several RAID 3 logical member > >drives. > > Perhaps a typo? Yes :-( Regards, Manuel.