Poor raid 1 performance?

Hi there,

I am planning on building a new computer system. Given the current cheap
price and massive capacity of hard drives, I am thinking of using a raid
array.

To me, raid 1 seems the ideal solution. Raid 1 greatly improves data
security, which is very important to me (and why I would never go with
raid 0). Theoretically, the performance of raid 1 should also be what I
want. Reads can be split across the two drives, leading to greater read
performance, while write performance might be slower. Given the way I
use the computer, read performance will help when it boots up, loads
applications, loads games, etc. On the other hand, the poorer write
performance will be less of an issue as much less is written to the disk
during typical use, and I tend to just leave the computer when
installing new programs (when large amounts of information does need to
be written to the disk).

Despite raid 1 seeming to be ideal, the read performance on current
motherboard raid chipsets shows little to no improvement compared to
that of a single drive:

http://techreport.com/reviews/2004q2...d/index.x?pg=1

Is it possible to get improved read performance using raid 1??

"Mark" wrote in message
...
Hi there,

I am planning on building a new computer system. Given the current cheap
price and massive capacity of hard drives, I am thinking of using a raid
array.

To me, raid 1 seems the ideal solution. Raid 1 greatly improves data
security, which is very important to me (and why I would never go with
raid 0). Theoretically, the performance of raid 1 should also be what I
want. Reads can be split across the two drives, leading to greater read
performance, while write performance might be slower. Given the way I use
the computer, read performance will help when it boots up, loads
applications, loads games, etc. On the other hand, the poorer write
performance will be less of an issue as much less is written to the disk
during typical use, and I tend to just leave the computer when installing
new programs (when large amounts of information does need to be written to
the disk).

Despite raid 1 seeming to be ideal, the read performance on current
motherboard raid chipsets shows little to no improvement compared to that
of a single drive:

http://techreport.com/reviews/2004q2...d/index.x?pg=1

Is it possible to get improved read performance using raid 1??

No! Raid 1 exists solely for data preservation ...you may be thinking of
RAID 1+0 which will give you redundancy plus a performance gain without
requiring a RAID 5 capable controller but as far as RAID 1 is concerned you
are mistaken in your belief that it will or should boost performance.

btb

Mark wrote:
Hi there,

I am planning on building a new computer system. Given the current
cheap price and massive capacity of hard drives, I am thinking of
using a raid array.

To me, raid 1 seems the ideal solution. Raid 1 greatly improves data
security, which is very important to me (and why I would never go with
raid 0). Theoretically, the performance of raid 1 should also be what
I want. Reads can be split across the two drives, leading to greater
read performance, while write performance might be slower. Given the
way I use the computer, read performance will help when it boots up,
loads applications, loads games, etc. On the other hand, the poorer
write performance will be less of an issue as much less is written to
the disk during typical use, and I tend to just leave the computer
when installing new programs (when large amounts of information does
need to be written to the disk).

Despite raid 1 seeming to be ideal, the read performance on current
motherboard raid chipsets shows little to no improvement compared to
that of a single drive:

http://techreport.com/reviews/2004q2...d/index.x?pg=1

Is it possible to get improved read performance using raid 1??

Why do you actually need improved read performance ?

Previously Mark wrote:
Hi there,

I am planning on building a new computer system. Given the current cheap
price and massive capacity of hard drives, I am thinking of using a raid
array.

To me, raid 1 seems the ideal solution. Raid 1 greatly improves data
security,

It improves safety. It does nothing at all for security.

which is very important to me (and why I would never go with
raid 0). Theoretically, the performance of raid 1 should also be what I
want. Reads can be split across the two drives, leading to greater read
performance, while write performance might be slower. Given the way I
use the computer, read performance will help when it boots up, loads
applications, loads games, etc. On the other hand, the poorer write
performance will be less of an issue as much less is written to the disk
during typical use, and I tend to just leave the computer when
installing new programs (when large amounts of information does need to
be written to the disk).

Despite raid 1 seeming to be ideal, the read performance on current
motherboard raid chipsets shows little to no improvement compared to
that of a single drive:

http://techreport.com/reviews/2004q2...d/index.x?pg=1

Is it possible to get improved read performance using raid 1??

Maybe, but it is not necessaruly done. E.g. Linux software RAID does
not speed up reads either. I don't quite know why, but there
is RAID10 where you combine a RAID0 layer and a RAID1 layer to get
speed and reliability, but also wor writes. My guess is that
speeding up reads is not enough of an issue to do RAID0 like
reading into the drivers/chips just for reading.

Arno

Bruce T. Berger wrote:

Is it possible to get improved read performance using raid 1??

No! Raid 1 exists solely for data preservation ...

Well, actually /my/ performance increased since I use RAID1 and don't have
to worry about the next disruptive hard drive crash anymore

Really, IMO there's little reason to run any computer that's used to store
critical data without RAID1 (or one of its derivatives).

Gerhard

Previously Gerhard Fiedler wrote:
Bruce T. Berger wrote:

Is it possible to get improved read performance using raid 1??

No! Raid 1 exists solely for data preservation ...

Well, actually /my/ performance increased since I use RAID1 and don't have
to worry about the next disruptive hard drive crash anymore

Very true!

Arno

Bruce T. Berger wrote:

"Mark" wrote in message
...


Hi there,

I am planning on building a new computer system. Given the current cheap
price and massive capacity of hard drives, I am thinking of using a raid
array.

To me, raid 1 seems the ideal solution. Raid 1 greatly improves data
security, which is very important to me (and why I would never go with
raid 0). Theoretically, the performance of raid 1 should also be what I
want. Reads can be split across the two drives, leading to greater read
performance, while write performance might be slower. Given the way I use
the computer, read performance will help when it boots up, loads
applications, loads games, etc. On the other hand, the poorer write
performance will be less of an issue as much less is written to the disk
during typical use, and I tend to just leave the computer when installing
new programs (when large amounts of information does need to be written to
the disk).

Despite raid 1 seeming to be ideal, the read performance on current
motherboard raid chipsets shows little to no improvement compared to that
of a single drive:

http://techreport.com/reviews/2004q2...d/index.x?pg=1

Is it possible to get improved read performance using raid 1??



No! Raid 1 exists solely for data preservation ...you may be thinking of
RAID 1+0 which will give you redundancy plus a performance gain without
requiring a RAID 5 capable controller but as far as RAID 1 is concerned you
are mistaken in your belief that it will or should boost performance.

btb




It is certainly possible with RAID1 to get better read throughput than
with a single HD, since RAID1 has twice as many on-disk read channels and
twice as many seek mechanisms. But, any increased read performance depends
on the workload (to have multiple reads outstanding) and on the RAID driver
(to not serialize the multiple outstanding reads).

I do agree that the primary reason for deploying RAID1 is data integrity
rather than performance, but modest performance gains have certainly been
measured (by me and by others) with good RAID1 implementations.

--
Cheers, Bob

Well, actually /my/ performance increased since I use RAID1 and don't have
to worry about the next disruptive hard drive crash anymore

But it doesn't mean that you should do nothing when one drive fails.

Really, IMO there's little reason to run any computer that's used to store
critical data without RAID1 (or one of its derivatives).

As little as a hundred bucks for a second disk and a new MB, if current does
not support RAID.

In , Bob Willard wrote:
since RAID1 has twice as many on-disk read channels
and twice as many seek mechanisms.

Yes, but also _any_ read is done twice, on both channels and both mechanisms
(and furthermore they are then checked for equality between, which adds a
step, which could be a reason for misperformance).

I do not see why you could see improvements, any other things being equal of
course.

What am I missing here?


Antoine

Why do you actually need improved read performance ?

He wants his computer to boot up faster and load games faster. To some
people an extra 10-20 seconds is eternity.