Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.os.linux.hardware > #3246

Re: Speed ups for a disk IO bound machine

From Peter Chant <pete@petezilla.co.uk>
Newsgroups comp.os.linux.hardware
Subject Re: Speed ups for a disk IO bound machine
Date 2016-12-10 20:44 +0000
Message-ID <eb37okF3tcbU1@mid.individual.net> (permalink)
References <earhh4F8si0U1@mid.individual.net> <5b6thd-pt2.ln1@lazy.lzy>

Show all headers | View raw

On 12/10/2016 11:43 AM, Piergiorgio Sartor wrote:
> On 2016-12-07 23:41, Peter Chant wrote:
> [...]
>> Any thoughts?
> 
> First of all, it would be good to know which kind
> of I/O is occuring.
> Is streaming read or write?
> Is random read or write?

Well, I've not taken any formal stats but a good part of the load is
mariadb at the same time as apache / php and firefox.  I'd assume random.

It looks like the mechanical drives are the ones with the biggest
noticeable usage.  The system SSD shows

> 
> In general, I usually would suggest to use 2 SSD
> in RAID-10 (Linux md).
> This will double the streaming read performance and,
> to certain extent, the random one.
> The write performance will be the same as 1 SSD.

I'm a bit confused here.  My understanding is that RAID10 requires four
disks, that they are striped in pairs and the pairs then mirror each
other.  So I can't do that if I have two drives.


> 
> Same for the HDDs, but possibly with some SSD (over
> RAID-10) caching.
> This because writing might be a bit slower (actually
> the FS RAM cache makes this not too observable).
> 

Again I have two hdds.  Raid10 with two SSDs and two HDDs would not make
sense to me, and I'm not convinced you are suggesting that. So perhaps
I've misunderstood.

This has got me thinking, rather than putting in the spare SSD only for
maria db I could bcache both HDDs.  Though I wince a bit at the lack of
symmetry in practice the drive with the system on it seems lightly used
and it is much larger.  If I get a SATA III controller that would speed
it up possibly offsetting any performance loss.  I'd still keep the main
system on a non-cached ssd only portion to keep boot devices much simpler.

> In this case, the question is if it is better to use
> bcache or lvmcache.
> This depend on the load. The second is an "hotspot"
> cache, meaning blocks frequently accessed are cached.
> The first is a more generic cache.
> Depending on use cases, one is better than the other.
> 

Hmm. bcache is simpler as a starting point.

> Hope this helps,
> 
> bye,
> 

Thanks.

Back to comp.os.linux.hardware | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-07 22:41 +0000
  Re: Speed ups for a disk IO bound machine Roger Blake <rogblake@iname.invalid> - 2016-12-08 16:44 +0000
    Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-10 11:24 +0000
      Re: Speed ups for a disk IO bound machine Roger Blake <rogblake@iname.invalid> - 2016-12-11 01:34 +0000
        Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-11 22:07 +0000
  Re: Speed ups for a disk IO bound machine Piergiorgio Sartor <piergiorgio.sartor.this.should.not.be.used@nexgo.REMOVETHIS.de> - 2016-12-10 12:43 +0100
    Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-10 20:44 +0000
      Re: Speed ups for a disk IO bound machine Piergiorgio Sartor <piergiorgio.sartor.this.should.not.be.used@nexgo.REMOVETHIS.de> - 2016-12-10 23:05 +0100
        Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-11 11:54 +0000
          Re: Speed ups for a disk IO bound machine Piergiorgio Sartor <piergiorgio.sartor.this.should.not.be.used@nexgo.REMOVETHIS.de> - 2016-12-11 14:10 +0100
            Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-11 22:46 +0000
              Re: Speed ups for a disk IO bound machine Piergiorgio Sartor <piergiorgio.sartor.this.should.not.be.used@nexgo.REMOVETHIS.de> - 2016-12-12 19:22 +0100
            Re: Speed ups for a disk IO bound machine David Brown <david.brown@hesbynett.no> - 2016-12-13 10:17 +0100
              Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-14 20:03 +0000
                Re: Speed ups for a disk IO bound machine David Brown <david.brown@hesbynett.no> - 2016-12-15 12:55 +0100
                Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-15 23:18 +0000
                Re: Speed ups for a disk IO bound machine David Brown <david.brown@hesbynett.no> - 2016-12-16 09:34 +0100
        Re: Speed ups for a disk IO bound machine David Brown <david.brown@hesbynett.no> - 2016-12-13 09:57 +0100
  Re: Speed ups for a disk IO bound machine David Brown <david.brown@hesbynett.no> - 2016-12-12 09:11 +0100
    Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-12 23:08 +0000
      Re: Speed ups for a disk IO bound machine David Brown <david.brown@hesbynett.no> - 2016-12-13 09:29 +0100
        Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-14 23:16 +0000
          Re: Speed ups for a disk IO bound machine David Brown <david.brown@hesbynett.no> - 2016-12-15 13:15 +0100
            Re: Speed ups for a disk IO bound machine Peter Chant <pete@petezilla.co.uk> - 2016-12-15 22:50 +0000
              Re: Speed ups for a disk IO bound machine David Brown <david.brown@hesbynett.no> - 2016-12-16 09:39 +0100

csiph-web