On Thu, 4 Mar 2004, Chuck Swiger wrote:
The parity calculations for RAID-5 are a lot of work and that work scales
linearly with the number of drives in the array. The longer you make the
array, the worse the performance becomes for small writes in particular.
How did you come to this
On Thu, 4 Mar 2004, Chuck Swiger wrote:
Also, RAID-5 performance degrades horribly if a drive is down, whereas RAID-1
does fine...
Using the algorithm you indicate below, RAID-5 performance would not
degrade on the loss of a drive, it's start out that badly.
A five-disk RAID-5 array has to
On Mar 5, 2004, at 5:57 AM, Jan Grant wrote:
How did you come to this conclusion? For a RAID 5 with a single parity
drive, the reason you zero the disks out completely on initialisation
is
to set up the integrity of the parity check. Then any update to any
RAID5 with single parity requires a read
On Thu, 4 Mar 2004 05:09, Chuck McManis wrote:
At 05:53 AM 3/3/2004, Danny Pansters wrote:
RAID5 on 3 disks? That's useless.
Its only mostly useless. You can't mirror (RAID-1) three drives, so if you
want some resiliency you can use RAID-5 and give up one disk to parity and
get two disks
Danny Pansters wrote:
[ ... ]
Physical disks are your unit of failure or of resilliance if you like.
Absolutely--- understanding RAID properly requires understanding the division
of data onto the physical disks. This is an important concept.
That's why you need 5+ drives for RAID5 to be any
Danny Pansters wrote:
So statistically and theoreticaly RAID1 compares to no RAID at all as 2x read
speed, 1x write speed (it needs to be written twice but through two heads on
two drives seperately and assume they react and move at the same speed).
That's about right, but you should be aware of
Hi!
Following up on this I'm also looking into buying some servers and have
the almost the same scenario, a MySQL DB together with apache with
mod_perl and embperl, (alot of SQL and dynamic content). Would we be
better off with:
Dual Xeon, 2.4 GHZ with 2GB of RAM or Xeon 3.0 GHZ with 2GB of RAM
On Wednesday 03 March 2004 14:05, Stefan Cars wrote:
Dual Xeon, 2.4 GHZ with 2GB of RAM or Xeon 3.0 GHZ with 2GB of RAM
and
RAID-1 on three disks or RAID-5 on three disks.
RAID5 on 3 disks? That's useless.
HTH,
Dan
___
[EMAIL PROTECTED] mailing
On Wed, Mar 03, 2004 at 02:53:49PM +0100, Danny Pansters wrote:
On Wednesday 03 March 2004 14:05, Stefan Cars wrote:
Dual Xeon, 2.4 GHZ with 2GB of RAM or Xeon 3.0 GHZ with 2GB of RAM
and
RAID-1 on three disks or RAID-5 on three disks.
RAID5 on 3 disks? That's useless.
3 disks is the
At 05:53 AM 3/3/2004, Danny Pansters wrote:
RAID5 on 3 disks? That's useless.
Its only mostly useless. You can't mirror (RAID-1) three drives, so if you
want some resiliency you can use RAID-5 and give up one disk to parity and
get two disks worth of data.
You could even do RAID4 on three disks.
Okey, but if you would compare RAID-1 on two disks compared to RAID-5 on
three disks then ? What would be the faster ?
/ Stefan
On Wed, 3 Mar 2004, Matthew Seaman wrote:
On Wed, Mar 03, 2004 at 02:53:49PM +0100, Danny Pansters wrote:
On Wednesday 03 March 2004 14:05, Stefan Cars wrote:
On Wed, Mar 03, 2004 at 10:26:43PM +0100, Stefan Cars wrote:
Okey, but if you would compare RAID-1 on two disks compared to RAID-5 on
three disks then ? What would be the faster ?
RAID1 is going to be faster, both reading and writing, but it will
take a lot more raw disk space to provide the
Ok. In this case the costs isn't really a problem, so both read and
write will be faster with two disks in a RAID1 vs. three disks in a RAID
5 ? I've read that RAID5 would be faster in read ?
/ Stefan
On Wed, 3 Mar 2004, Matthew Seaman wrote:
On Wed, Mar 03, 2004 at 10:26:43PM +0100, Stefan
RAID-1 will be about 50% faster than RAID-5 doing reads regardless of
size, and will also be *much* faster doing small writes-- by a factor
of 4, perhaps.
The abovementioned figures seem more like comparing RAID-0 (striping)
to RAID-5 (striping with ECC) than RAID-5 to RAID-1 (mirroring).
On Mar 3, 2004, at 5:20 PM, Reko Turja wrote:
RAID-1 will be about 50% faster than RAID-5 doing reads regardless of
size, and will also be *much* faster doing small writes-- by a factor
of 4, perhaps.
The abovementioned figures seem more like comparing RAID-0 (striping)
to RAID-5 (striping with
(enough CCing, back to list only)
On Wednesday 03 March 2004 22:36, Matthew Seaman wrote:
On Wed, Mar 03, 2004 at 10:26:43PM +0100, Stefan Cars wrote:
Okey, but if you would compare RAID-1 on two disks compared to RAID-5 on
three disks then ? What would be the faster ?
RAID1 is going to be
On Wednesday 03 March 2004 23:20, Reko Turja wrote:
RAID-1 will be about 50% faster than RAID-5 doing reads regardless of
size, and will also be *much* faster doing small writes-- by a factor
of 4, perhaps.
The abovementioned figures seem more like comparing RAID-0 (striping)
to RAID-5
Stefan Cars wrote:
Ok. In this case the costs isn't really a problem, so both read and
write will be faster with two disks in a RAID1 vs. three disks in a RAID
5 ? I've read that RAID5 would be faster in read ?
Short answer- it depends. Bear in mind that there are some controllers
that will do
Stefan Cars wrote:
Hi!
Following up on this I'm also looking into buying some servers and have
the almost the same scenario, a MySQL DB together with apache with
mod_perl and embperl, (alot of SQL and dynamic content). Would we be
better off with:
Dual Xeon, 2.4 GHZ with 2GB of RAM or Xeon 3.0
I would use the P III with the 5. branch of freebsd and the appropriate
configuration of mysql.
Yoan
I'm putting together a system that will host a relatively small database
(around 20,000 records), as well as run Apache / PHP to search that
database. I have the option in front of me to use a
Joseph Koenig wrote:
I'm putting together a system that will host a relatively small database
(around 20,000 records), as well as run Apache / PHP to search that
database. I have the option in front of me to use a P III dual 1GHz machine
with a SCSI Raid 5, or to use a single P4 2.8 GHz with a
Joseph Koenig wrote:
I'm putting together a system that will host a relatively small database
(around 20,000 records), as well as run Apache / PHP to search that
database. I have the option in front of me to use a P III dual 1GHz machine
with a SCSI Raid 5, or to use a single P4 2.8 GHz with a
Joseph Koenig wrote:
I'm putting together a system that will host a relatively small database
(around 20,000 records), as well as run Apache / PHP to search that
database. I have the option in front of me to use a P III dual 1GHz machine
with a SCSI Raid 5, or to use a single P4 2.8 GHz with a
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