I'm trying to work out the kinks of a proprietary, old, and clunky application that runs on CentOS. One of its main problems is that it writes image sequences extremely non-linearly and in several passes, using many CPUs, so the sequences get very fragmented.
The obvious solution to this seems to be to use SSDs for its output, and some scripts that will pick up and copy our the sequences in proper order once it's done. I have two 512GB SSDs, and I've used LVM to set up a RAID0 between them.
I've got that part running, but since I'm on CentOS 5.8 (which is what this application officially supports), I don't have a kernel with SSD discard support, and after a few days (I told you, this application is write intensive), things get very slow.
Using hdparm to secure erase the drives and recreating the LVM RAID0 gets things back to speed again, but that's obviously not ideal.
So, from what I understand, if I can get this thing running on CentOS 6.4, I'll get kernel discard support, and discard support in LVM when running a RAID0. I'm using ext4.
Is that correct? Will this solve my problem? I want to confirm that discard support works on a RAID0 of SSDs using LVM and ext4 before I start working on getting this legacy application to run on a newer CentOS.
On 19.08.2013 20:28, Joakim Ziegler wrote:
I'm trying to work out the kinks of a proprietary, old, and clunky application that runs on CentOS. One of its main problems is that it writes image sequences extremely non-linearly and in several passes, using many CPUs, so the sequences get very fragmented.
The obvious solution to this seems to be to use SSDs for its output, and some scripts that will pick up and copy our the sequences in proper order once it's done. I have two 512GB SSDs, and I've used LVM to set up a RAID0 between them.
I've got that part running, but since I'm on CentOS 5.8 (which is what this application officially supports), I don't have a kernel with SSD discard support, and after a few days (I told you, this application is write intensive), things get very slow.
Using hdparm to secure erase the drives and recreating the LVM RAID0 gets things back to speed again, but that's obviously not ideal.
So, from what I understand, if I can get this thing running on CentOS 6.4, I'll get kernel discard support, and discard support in LVM when running a RAID0. I'm using ext4.
Is that correct? Will this solve my problem? I want to confirm that discard support works on a RAID0 of SSDs using LVM and ext4 before I start working on getting this legacy application to run on a newer CentOS.
What kind of SSD are you using? We use Intel 520's here and don't really see these kind of slowdowns.
Regards, Dennis
On 2013-08-20 13:20, Dennis Jacobfeuerborn wrote:
On 19.08.2013 20:28, Joakim Ziegler wrote:
So, from what I understand, if I can get this thing running on CentOS 6.4, I'll get kernel discard support, and discard support in LVM when running a RAID0. I'm using ext4.
Is that correct? Will this solve my problem? I want to confirm that discard support works on a RAID0 of SSDs using LVM and ext4 before I start working on getting this legacy application to run on a newer CentOS.
What kind of SSD are you using? We use Intel 520's here and don't really see these kind of slowdowns.
Seeing his problem I remember I saw a similar complain about SSD and write rate. Searching my recent archives it appears its neither on such an "old" kernel nor on RAID0.
For what it's worth: http://www.mail-archive.com/collectd@verplant.org/msg02683.html
On Tue, Aug 20, 2013 at 12:20:01PM +0200, Dennis Jacobfeuerborn wrote:
On 19.08.2013 20:28, Joakim Ziegler wrote:
I'm trying to work out the kinks of a proprietary, old, and clunky application that runs on CentOS. One of its main problems is that it writes image sequences extremely non-linearly and in several passes, using many CPUs, so the sequences get very fragmented.
The obvious solution to this seems to be to use SSDs for its output, and some scripts that will pick up and copy our the sequences in proper order once it's done. I have two 512GB SSDs, and I've used LVM to set up a RAID0 between them.
I've got that part running, but since I'm on CentOS 5.8 (which is what this application officially supports), I don't have a kernel with SSD discard support, and after a few days (I told you, this application is write intensive), things get very slow.
Using hdparm to secure erase the drives and recreating the LVM RAID0 gets things back to speed again, but that's obviously not ideal.
So, from what I understand, if I can get this thing running on CentOS 6.4, I'll get kernel discard support, and discard support in LVM when running a RAID0. I'm using ext4.
Is that correct? Will this solve my problem? I want to confirm that discard support works on a RAID0 of SSDs using LVM and ext4 before I start working on getting this legacy application to run on a newer CentOS.
What kind of SSD are you using? We use Intel 520's here and don't really see these kind of slowdowns.
You can also check a newer kernel for CentOS 5 from ELrepo:
Mihai
On 20/08/13 5:39, Mihai T. Lazarescu wrote:
On Tue, Aug 20, 2013 at 12:20:01PM +0200, Dennis Jacobfeuerborn wrote:
Is that correct? Will this solve my problem? I want to confirm that discard support works on a RAID0 of SSDs using LVM and ext4 before I start working on getting this legacy application to run on a newer CentOS.
What kind of SSD are you using? We use Intel 520's here and don't really see these kind of slowdowns.
You can also check a newer kernel for CentOS 5 from ELrepo:
http://elrepo.org/
That's an excellent suggestion, thanks.
However, can anyone confirm that this in fact works? That is, that LVM RAID0 of two SSDs and ext4 will allow the file system to issue discards to the underlying devices?
So, can anyone confirm that discards work on ext4 a LVM RAID0 of two SSDs with CentOS 6.4 or the latest ElRepo kernel for Centos 5.8?
This should be a fairly simple question, either it works or it doesn't...
On 08/21/2013 11:42 PM, Joakim Ziegler wrote:
So, can anyone confirm that discards work on ext4 a LVM RAID0 of two SSDs with CentOS 6.4 or the latest ElRepo kernel for Centos 5.8?
This should be a fairly simple question, either it works or it doesn't...
hi,
First hit: https://www.google.com/search?q=ssd%20rhel
Yes, I read that, I was wondering if anyone had actual experience.
Lacking that, I tried to just set it up. So far, it seems like it's working, mkfs.ext4 did discards on format, and I can mount with the discard option. I'm currently running some batches on it to see if speeds keeps up, but it's looking good.
These are Crucial M4s.
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Dennis Jacobfeuerborn -
Joakim Ziegler -
Mihai T. Lazarescu -
Mihamina Rakotomandimby -
natxo asenjo