Hi,

i don't know much about hard disks and raid controllers but often there is
some discussion about which raid controller rocks and which sucks. my hosting
company offers me a raid 10 with 4 serial-ata disks. They will use a "3ware
4-Port-RAID-Controller 9500S"

More than 4 disks are not possible. Most operations and all time-critical
operations are read-only using a lot of indices. My partioning plans are like
this:

disk 1: OS, tablespace
disk 2: indices, WAL, Logfiles

- Does my partitioning make sense?
- I want to know if 3ware 9500 S is recommended or if its one of those
controllers which sucks.

kind regards,
janning

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  • Merlin Moncure at Apr 12, 2006 at 4:31 pm

    On 4/12/06, Janning Vygen wrote:
    Hi,
    disk 1: OS, tablespace
    disk 2: indices, WAL, Logfiles
    - Does my partitioning make sense?
    with raid 10 all four drives will appear as a single physical device
    shared by all. I'm personally not a big fan of logical partitioning
    of a single raid device unless you are trying to keep a physical
    volume under 1 TB for example. Each sync on the volume is guaranteed
    to sync all 4 disks regardless of how you set your partitions up.
    - I want to know if 3ware 9500 S is recommended or if its one of those
    controllers which sucks.
    escalade is a fairly full featured raid controller for the price.
    consider it the ford taurus of raid controllers, it's functional and
    practical but not sexy. Their S line is not native sata but operates
    over a pata->sata bridge. Stay away from raid 5.

    merlin
  • Janning Vygen at Apr 12, 2006 at 5:31 pm
    Thanks for your fast reply.

    Am Mittwoch, 12. April 2006 18:31 schrieb Merlin Moncure:
    On 4/12/06, Janning Vygen wrote:
    Hi,
    disk 1: OS, tablespace
    disk 2: indices, WAL, Logfiles
    - Does my partitioning make sense?
    with raid 10 all four drives will appear as a single physical device
    shared by all. I'm personally not a big fan of logical partitioning
    of a single raid device unless you are trying to keep a physical
    volume under 1 TB for example. Each sync on the volume is guaranteed
    to sync all 4 disks regardless of how you set your partitions up.
    Ok, i am not a raid expert. but in my understanding RAID 10 is faster than two
    RAID 1 arrays, aren't they? So, given that i can put up to 4 S-ATA disk in my
    server and the mentioned raid controller. Would you prefer no-raid, RAID1 or
    RAID 10?
    - I want to know if 3ware 9500 S is recommended or if its one of those
    controllers which sucks.
    escalade is a fairly full featured raid controller for the price.
    consider it the ford taurus of raid controllers, it's functional and
    practical but not sexy. Their S line is not native sata but operates
    over a pata->sata bridge. Stay away from raid 5.
    thanks for your recommendation. ford taurus is ok for me :-)

    kind regrads
    janning
  • Ted Byers at Apr 12, 2006 at 6:11 pm

    ----- Original Message -----
    From: "Merlin Moncure" <mmoncure@gmail.com>
    To: "Janning Vygen" <vygen@gmx.de>
    Cc: <pgsql-general@postgresql.org>
    Sent: Wednesday, April 12, 2006 12:31 PM
    Subject: Re: [GENERAL] Hardware related question: 3ware 9500S
    [snip]
    - I want to know if 3ware 9500 S is recommended or if its one of those
    controllers which sucks.
    escalade is a fairly full featured raid controller for the price.
    consider it the ford taurus of raid controllers, it's functional and
    practical but not sexy. Their S line is not native sata but operates
    over a pata->sata bridge. Stay away from raid 5.
    Hi Merlin

    Why? What's wrong with raid 5? I could well be wrong (given how little
    attention I have paid to hardware over the past few years because of a focus
    on developing software), but I was under the impression that of the raid
    options available, raid 5 with hot swappable drives provided good data
    protection and performance at a reasonably low cost. Is the problem with
    the concept of raid 5, or the common implementations?

    Do you have a recommendation regarding whether the raid array is built into
    the server running the RDBMS (in our case PostgreSQL), or located in a
    network appliance dedicated to storing the data managed by the RDBMS? If
    you were asked to design a subnet that provides the best possible
    performance and protection of the data, but without gold-plating anything,
    what would you do? How much redundancy would you build in, and at what
    granularity?

    Ted
  • Scott Marlowe at Apr 12, 2006 at 6:24 pm

    On Wed, 2006-04-12 at 13:10, Ted Byers wrote:
    ----- Original Message -----
    From: "Merlin Moncure" <mmoncure@gmail.com>
    To: "Janning Vygen" <vygen@gmx.de>
    Cc: <pgsql-general@postgresql.org>
    Sent: Wednesday, April 12, 2006 12:31 PM
    Subject: Re: [GENERAL] Hardware related question: 3ware 9500S
    [snip]
    - I want to know if 3ware 9500 S is recommended or if its one of those
    controllers which sucks.
    escalade is a fairly full featured raid controller for the price.
    consider it the ford taurus of raid controllers, it's functional and
    practical but not sexy. Their S line is not native sata but operates
    over a pata->sata bridge. Stay away from raid 5.
    Hi Merlin

    Why? What's wrong with raid 5? I could well be wrong (given how little
    attention I have paid to hardware over the past few years because of a focus
    on developing software), but I was under the impression that of the raid
    options available, raid 5 with hot swappable drives provided good data
    protection and performance at a reasonably low cost. Is the problem with
    the concept of raid 5, or the common implementations?

    Do you have a recommendation regarding whether the raid array is built into
    the server running the RDBMS (in our case PostgreSQL), or located in a
    network appliance dedicated to storing the data managed by the RDBMS? If
    you were asked to design a subnet that provides the best possible
    performance and protection of the data, but without gold-plating anything,
    what would you do? How much redundancy would you build in, and at what
    granularity?
    There have been NUMEROUS discussions of RAID-5 versus RAID 1+0 in the
    perform group in the last year or two. Short version:

    RAID 5 is useful, with large numbers of drives, for OLAP type databases,
    where you're trying to get as much storage as possible from your
    drives. RAID 5 pretty much REQUIRES battery backed cache for decent
    write performance, and even then, will saturate faster than RAID 1+0.
    RAID-5 cannot survive multiple simultaneous drive failures.

    RAID 1+0 requires better than average controllers, since many serialize
    and lockstep data through the various layers of RAID on them. It
    provides less storage for a given number of drives. It is faster for
    OLTP workloads than RAID-5. RAID 1+0 can survive multiple drive
    failures as long as two drives in the same mirror set do not fail at
    once.

    With increasing number of drives, the chances of a RAID 5 failing go up
    linearly, while the chances of RAID 1+0 failing due to multiple drive
    failure stay the same.
  • Ted Byers at Apr 12, 2006 at 6:53 pm
    ----- Original Message -----
    From: "Scott Marlowe" <smarlowe@g2switchworks.com>
    To: "Ted Byers" <r.ted.byers@rogers.com>
    Cc: "Merlin Moncure" <mmoncure@gmail.com>; "Janning Vygen" <vygen@gmx.de>;
    "pgsql general" <pgsql-general@postgresql.org>
    Sent: Wednesday, April 12, 2006 2:24 PM
    Subject: Re: [GENERAL] Hardware related question: 3ware 9500S

    On Wed, 2006-04-12 at 13:10, Ted Byers wrote:
    ----- Original Message -----
    From: "Merlin Moncure" <mmoncure@gmail.com>
    To: "Janning Vygen" <vygen@gmx.de>
    Cc: <pgsql-general@postgresql.org>
    Sent: Wednesday, April 12, 2006 12:31 PM
    Subject: Re: [GENERAL] Hardware related question: 3ware 9500S
    [snip]
    Why? What's wrong with raid 5? I could well be wrong (given how little
    attention I have paid to hardware over the past few years because of a
    focus
    on developing software), but I was under the impression that of the raid
    options available, raid 5 with hot swappable drives provided good data
    protection and performance at a reasonably low cost. Is the problem with
    the concept of raid 5, or the common implementations?

    Do you have a recommendation regarding whether the raid array is built
    into
    the server running the RDBMS (in our case PostgreSQL), or located in a
    network appliance dedicated to storing the data managed by the RDBMS? If
    you were asked to design a subnet that provides the best possible
    performance and protection of the data, but without gold-plating
    anything,
    what would you do? How much redundancy would you build in, and at what
    granularity?
    There have been NUMEROUS discussions of RAID-5 versus RAID 1+0 in the
    perform group in the last year or two. Short version:
    Interesting.

    I take it that "RAID 1+0" refers to a combination of Raid 1 and RAID 0.
    What about RAID 10? I am curious because RAID 10 has come out since the
    last time I took a look at RAID technology. I am not sure what it actually
    does differently from RAID 5.

    This question of data security is becoming of increasing importance to me
    professionally since I will soon have to advise the company I'm working with
    regarding how best to secure the data managed by the applications I'm
    developing for them. I will need overall guidelines to produce a design
    that makes it virtually impossible for them to lose even on field in one
    record. The data is both sensitive and vital. Fortunately, I have a few
    months before we need to commit to anything. Also, fortunately, with one
    exception, the applications rely on a data feed that comes in once a day
    after normal working hours, so I won't have to worry about writes to the DB
    other than what my script does to load the datafeed into the DB. All other
    access is read only. This should make it easier to produce a strategy to
    protect the data from any kind of technology failure (software or hardware).
    Cost is a factor, but reliability is much much more important!

    Thanks,

    Ted
  • Martijn van Oosterhout at Apr 12, 2006 at 7:02 pm

    On Wed, Apr 12, 2006 at 02:53:01PM -0400, Ted Byers wrote:
    I take it that "RAID 1+0" refers to a combination of Raid 1 and RAID 0.
    What about RAID 10? I am curious because RAID 10 has come out since the
    last time I took a look at RAID technology. I am not sure what it actually
    does differently from RAID 5.
    AIUI, RAID 10 = RAID 1+0. Lame, I know. Similarly, some people have
    invented RAID 50 = RAID 5+0.

    Not sure if that's the official definition though, but that's the way
    I've seen it used.
    --
    Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
    Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
    tool for doing 5% of the work and then sitting around waiting for someone
    else to do the other 95% so you can sue them.
  • Geoffrey at Apr 12, 2006 at 7:13 pm

    Martijn van Oosterhout wrote:
    On Wed, Apr 12, 2006 at 02:53:01PM -0400, Ted Byers wrote:
    I take it that "RAID 1+0" refers to a combination of Raid 1 and RAID 0.
    What about RAID 10? I am curious because RAID 10 has come out since the
    last time I took a look at RAID technology. I am not sure what it actually
    does differently from RAID 5.
    AIUI, RAID 10 = RAID 1+0. Lame, I know. Similarly, some people have
    invented RAID 50 = RAID 5+0.

    Not sure if that's the official definition though, but that's the way
    I've seen it used.
    Useful info on RAID definitions:

    http://tinyurl.com/zhnmc

    --
    Until later, Geoffrey

    Any society that would give up a little liberty to gain a little
    security will deserve neither and lose both. - Benjamin Franklin
  • Scott Marlowe at Apr 12, 2006 at 7:49 pm

    On Wed, 2006-04-12 at 13:53, Ted Byers wrote:
    ----- Original Message -----
    From: "Scott Marlowe" <smarlowe@g2switchworks.com>
    There have been NUMEROUS discussions of RAID-5 versus RAID 1+0 in the
    perform group in the last year or two. Short version:
    Interesting. SNIP
    This question of data security is becoming of increasing importance to me
    professionally since I will soon have to advise the company I'm working with
    regarding how best to secure the data managed by the applications I'm
    developing for them. I will need overall guidelines to produce a design
    that makes it virtually impossible for them to lose even on field in one
    record. The data is both sensitive and vital. Fortunately, I have a few
    months before we need to commit to anything. Also, fortunately, with one
    exception, the applications rely on a data feed that comes in once a day
    after normal working hours, so I won't have to worry about writes to the DB
    other than what my script does to load the datafeed into the DB. All other
    access is read only. This should make it easier to produce a strategy to
    protect the data from any kind of technology failure (software or hardware).
    Cost is a factor, but reliability is much much more important!
    When you say reliability, I'm not sure your definition is my
    definition. Is is that the database MUST be up during business hours,
    even if the updates that happen during the day can't go through? Or
    even if those updates get lost and have to be re-entered that's OK, as
    long as the data entered by the batch file at night is available for
    business processes.

    There are a lot of ways to set this up, and each tool in the tool box
    has its advantages and disadvantages. PITR, Slony Replication, pgpool,
    pgcluster, mammoth replicator, bizgress, bizgress MPP...

    I'd guess that the data entered during the day is the most important.
    If this is so, you could set up slony replication on those tables to a
    backup machine so that should the primary suffer catastrophic failure
    you still have the inputs.

    RAID is great, but it's no replacement for replication and / or point in
    time recovery. More an augment.
  • Merlin Moncure at Apr 12, 2006 at 7:18 pm

    On 4/12/06, Ted Byers wrote:
    ----- Original Message -----
    From: "Merlin Moncure" <mmoncure@gmail.com>
    To: "Janning Vygen" <vygen@gmx.de>
    Cc: <pgsql-general@postgresql.org>
    Sent: Wednesday, April 12, 2006 12:31 PM
    Subject: Re: [GENERAL] Hardware related question: 3ware 9500S
    [snip]
    - I want to know if 3ware 9500 S is recommended or if its one of those
    controllers which sucks.
    escalade is a fairly full featured raid controller for the price.
    consider it the ford taurus of raid controllers, it's functional and
    practical but not sexy. Their S line is not native sata but operates
    over a pata->sata bridge. Stay away from raid 5.
    Hi Merlin

    Why? What's wrong with raid 5? I could well be wrong (given how little
    there are reasons to go with raid 5 or other raids. where I work we
    often do 14 drive raid 6 plus 1 hot swap on a 15 drive tray. However,
    for 4 drive raid, I think 0+1 is the by far the best choice. For
    three drive, I'd suggest two drive raid 1 plus hot swap.
    Do you have a recommendation regarding whether the raid array is built into
    the server running the RDBMS (in our case PostgreSQL), or located in a
    network appliance dedicated to storing the data managed by the RDBMS? If
    you were asked to design a subnet that provides the best possible
    performance and protection of the data, but without gold-plating anything,
    what would you do? How much redundancy would you build in, and at what
    granularity?
    I would stay clear of cheaper NAS solutions (AoE, iscsi) unless you
    really didn't care about performance. In my experience the better
    SANs are a good way to go if you need flexibility or easy managment
    (especially if you need to do things besides database) without losing
    performance. A good SAN makes everything easy but boy do you pay for
    it.

    If you want most bang for the buck, I'd suggest either attached scsi
    or sata (especially the latter). With sata, 24 raptors will get you
    insane performance for a very reasonable price. Most of my apps are
    cpu bound anyways.
  • Francisco Reyes at Apr 15, 2006 at 2:41 pm

    Merlin Moncure writes:

    there are reasons to go with raid 5 or other raids. where I work we
    often do 14 drive raid 6 plus 1 hot swap on a 15 drive tray.
    Raid 5 is different from raid 6.... To say that there are times it's ok to
    use RAID 5 and then say you use raid 6... well... doesn't really say
    anything about raid 5.

    Also, what controller are you using?
    From what I gather, raid 6 is less common and fewer cards support it (areca
    is one of them I believe).
  • Francisco Reyes at Apr 15, 2006 at 2:36 pm

    Merlin Moncure writes:

    escalade is a fairly full featured raid controller for the price.
    consider it the ford taurus of raid controllers, it's functional and
    practical but not sexy. Their S line is not native sata but operates
    over a pata->sata bridge. Stay away from raid 5.
    Do you know if their raid 5 is better in the new 9550SX?

    Or is the "Stay away from raid 5" more of a general comment that this type
    of raid is not good for DBs?
  • Alex Turner at Apr 15, 2006 at 5:21 pm
    Raid 5 on the 9550SX is supposed to be significantly better than the 9500
    series.

    I would be carefull of benchmarks listed out there. For instance, whilst
    looking for supporting material, I came cross this gem:
    http://www.gamepc.com/labs/print_content.asp?id=9550sx4lp&cookie%5Ftest=1

    They claim the they used a Tyan Thunder K8WE motherboard, and installed the
    RAID controllers in a 64-bit 133MHz PCI-X slot. This motherboard doesn't
    have any 64-bit 133Mhz PCI-X slots! (
    http://www.tyan.com/products/html/tigerk8we_spec.html).
    It's no wonder that the other raid controllers showed significantly less
    performance than the PCI-e card.

    This review from tomshardware:
    http://www.tomshardware.com/2005/10/31/sata_spells_trouble_for_scsi_raid/page13.html

    Suggests that the 9550SX is at least competitive with the others.

    I know I like the 3ware/AMCC cards because of their very good RAID 10
    performance. I'm not a big RAID 5 fan. RAID 5 sufferes the read before
    write penalty problem that make RAID 5 writes very slow, particularly
    noticebale in OLTP applications. RAID 10 will almost always offer better
    write perfomance.

    I wish we could set up an organization to do benchmarks with pgbench on
    various different RAID controllers/drives and publish the results. I know I
    would pay money for that.

    Alex
    On 4/15/06, Francisco Reyes wrote:

    Merlin Moncure writes:
    escalade is a fairly full featured raid controller for the price.
    consider it the ford taurus of raid controllers, it's functional and
    practical but not sexy. Their S line is not native sata but operates
    over a pata->sata bridge. Stay away from raid 5.
    Do you know if their raid 5 is better in the new 9550SX?

    Or is the "Stay away from raid 5" more of a general comment that this type
    of raid is not good for DBs?

    ---------------------------(end of broadcast)---------------------------
    TIP 4: Have you searched our list archives?

    http://archives.postgresql.org
  • Francisco Reyes at Apr 15, 2006 at 10:35 pm

    Alex Turner writes:

    Suggests that the 9550SX is at least competitive with the others.
    Thanks for the links.
    I know I like the 3ware/AMCC cards because of their very good RAID 10
    performance.
    Raid 10 is what I used on my last server and likely what I will use on the
    next.

    I wish we could set up an organization to do benchmarks with pgbench on
    various different RAID controllers/drives and publish the results.  I know
    I would pay money for that.
    Yes. That would be truly very usefull, although it would be very time
    consuming.
  • Alex Turner at Apr 16, 2006 at 2:38 am
    I have the time to do it, but not the $$s ;)

    Alex
    On 4/15/06, Francisco Reyes wrote:

    Alex Turner writes:
    Suggests that the 9550SX is at least competitive with the others.
    Thanks for the links.
    I know I like the 3ware/AMCC cards because of their very good RAID 10
    performance.
    Raid 10 is what I used on my last server and likely what I will use on the
    next.

    I wish we could set up an organization to do benchmarks with pgbench on
    various different RAID controllers/drives and publish the results. I know
    I would pay money for that.
    Yes. That would be truly very usefull, although it would be very time
    consuming.
  • Guy Rouillier at Apr 15, 2006 at 8:03 pm

    Alex Turner wrote:
    Raid 5 on the 9550SX is supposed to be significantly better than the
    9500 series.

    I would be carefull of benchmarks listed out there. For instance,
    whilst looking for supporting material, I came cross this gem:
    http://www.gamepc.com/labs/print_content.asp?id=9550sx4lp&cookie%5Ftest=
    1
    They claim the they used a Tyan Thunder K8WE motherboard, and
    installed the RAID controllers in a 64-bit 133MHz PCI-X slot. This
    motherboard doesn't have any 64-bit 133Mhz PCI-X slots! (
    http://www.tyan.com/products/html/tigerk8we_spec.html).
    It's no wonder that the other raid controllers showed significantly
    less performance than the PCI-e card.
    You're looking at the wrong board. They are talking about the Tyan
    *Thunder*, which does indeed have 64-bit PCI-X. You are looking at the
    Tyan **Tiger**, which does not.

    --
    Guy Rouillier
  • Alex Turner at Apr 16, 2006 at 2:38 am
    Ahhhh... good point.

    Why oh why does tyan have two boards with the same prefix ;)!!!

    Alex
    On 4/15/06, Guy Rouillier wrote:

    Alex Turner wrote:
    Raid 5 on the 9550SX is supposed to be significantly better than the
    9500 series.

    I would be carefull of benchmarks listed out there. For instance,
    whilst looking for supporting material, I came cross this gem:
    http://www.gamepc.com/labs/print_content.asp?id=9550sx4lp&cookie%5Ftest=
    1
    They claim the they used a Tyan Thunder K8WE motherboard, and
    installed the RAID controllers in a 64-bit 133MHz PCI-X slot. This
    motherboard doesn't have any 64-bit 133Mhz PCI-X slots! (
    http://www.tyan.com/products/html/tigerk8we_spec.html).
    It's no wonder that the other raid controllers showed significantly
    less performance than the PCI-e card.
    You're looking at the wrong board. They are talking about the Tyan
    *Thunder*, which does indeed have 64-bit PCI-X. You are looking at the
    Tyan **Tiger**, which does not.

    --
    Guy Rouillier

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