Re: Disk I/O slowness
"Alexander V. Makartsev" <[email protected]> Fri, 31 Jul 2026 12:41:24 +0500
| Newsgroups | gmane.linux.debian.user |
|---|---|
| Message-ID | <[email protected]> |
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On 7/31/26 01:09, Andy Smith wrote:
> Hi,
>
> On Fri, Jul 31, 2026 at 12:04:30AM +0500, Alexander V. Makartsev wrote:
>> I might add insult to the injury, but are you sure you need RAID-5 if it
>> consists of just 3 drives?
>> Usually around 30% per drive's capacity will be sacrificed to hold error
>> correction data for the array,
>> so maybe it will be much better to use 2 drives in RAID-1 (Mirror)
>> configuration, if you need decent write performance.
>> Third drive could be used as spare device for the array, or a separate
>> storage without redundancy.
> On Linux mdadm you can also do a RAID-10 across three drives which still
> allows for the loss of any single drive and provides both better read
> and write performance compared to RAID-5 of the same devices. The
> capacity would be 1.5 drives as opposed to 2.
That is an interesting idea.
The RAID-10 configuration you proposing should then consist of 3 RAID-1
(mirror) groups, so 3 drives must be partitioned in halves and to finish
RAID-10 array, there should be a RAID-0 (stripe) array created across
all 3 groups.
Will the RAID-0 (stripping) layer of RAID-10 configuration significantly
improve the write performance of the array in comparison to a basic
RAID-1 array?
With the today's abysmal prices of storage devices of any kind, I don't
think I will be able to test this any time soon...
--
With kindest regards, Alexander.
Debian - The universal operating system
https://www.debian.org
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<div class="moz-cite-prefix">On 7/31/26 01:09, Andy Smith wrote:<br>
</div>
<blockquote type="cite" cite="mid:[email protected]">
<pre wrap="" class="moz-quote-pre">Hi,
On Fri, Jul 31, 2026 at 12:04:30AM +0500, Alexander V. Makartsev wrote:
</pre>
<blockquote type="cite">
<pre wrap="" class="moz-quote-pre">I might add insult to the injury, but are you sure you need RAID-5 if it
consists of just 3 drives?
Usually around 30% per drive's capacity will be sacrificed to hold error
correction data for the array,
so maybe it will be much better to use 2 drives in RAID-1 (Mirror)
configuration, if you need decent write performance.
Third drive could be used as spare device for the array, or a separate
storage without redundancy.
</pre>
</blockquote>
<pre wrap="" class="moz-quote-pre">
On Linux mdadm you can also do a RAID-10 across three drives which still
allows for the loss of any single drive and provides both better read
and write performance compared to RAID-5 of the same devices. The
capacity would be 1.5 drives as opposed to 2.</pre>
</blockquote>
That is an interesting idea.<br>
The RAID-10 configuration you proposing should then consist of 3
RAID-1 (mirror) groups, so 3 drives must be partitioned in halves
and to finish RAID-10 array, there should be a RAID-0 (stripe) array
created across all 3 groups.<br>
<br>
Will the RAID-0 (stripping) layer of RAID-10 configuration
significantly improve the write performance of the array in
comparison to a basic RAID-1 array?<br>
With the today's abysmal prices of storage devices of any kind, I
don't think I will be able to test this any time soon...<br>
<br>
<div class="moz-signature">-- <br>
<pre style="font-size: .8rem;"> With kindest regards, Alexander.</pre>
<img src="cid:[email protected]" alt=""
style="float:left; display:inline;">
<pre style="display:inline; font-size: .6rem;"> Debian - The universal operating system
<a href="https://www.debian.org" class="moz-txt-link-freetext">https://www.debian.org</a></pre>
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