Silly stripe cache values

Silly stripe cache values

[Brad Campbell]

G'day all,

I have a box here.. it has a 2Ghz processor and 1.5GB of ram. It runs the entire OS over NFS and 
it's sole purpose in life is to run 15 SATA drives in a Raid-6 with ext3 on it, and share that over 
NFS. Most of that ram is sitting completely idle and thus I thought a logical thing to do would be 
to stuff as much of it as possible into the MD subsystem to help it cache..

Are there any limits to the values living in /sys/block/md* and what might be the tradeoffs (if any) 
to using what would normally be thought stupid amounts of ram for these knobs ?

This box does not get written to often, it's just a media streamer mostly.. but if I am writing to 
it then it chokes just providing a 1Mb stream over the network currently. (It's on a 2.6.15-git11 
kernel currently but I'm just upgrading to 2.6.16 now)

Regards,
Brad
-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

Re: Silly stripe cache values

[Brad Campbell]

Brad Campbell wrote:
> G'day all,
> 
> I have a box here.. it has a 2Ghz processor and 1.5GB of ram. It runs 
> the entire OS over NFS and it's sole purpose in life is to run 15 SATA 
> drives in a Raid-6 with ext3 on it, and share that over NFS. Most of 
> that ram is sitting completely idle and thus I thought a logical thing 
> to do would be to stuff as much of it as possible into the MD subsystem 
> to help it cache..
> 
> Are there any limits to the values living in /sys/block/md* and what 
> might be the tradeoffs (if any) to using what would normally be thought 
> stupid amounts of ram for these knobs ?
> 
> This box does not get written to often, it's just a media streamer 
> mostly.. but if I am writing to it then it chokes just providing a 1Mb 
> stream over the network currently. (It's on a 2.6.15-git11 kernel 
> currently but I'm just upgrading to 2.6.16 now)

Scratch that.. the limit appears to be 32768 and that works fine..

Google search results increase in accuracy proportionally with the elapsed time of a list posting 
with the question.. :\

Brad
-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

[PATCH] Add stripe cache entries to raid6 sysfs

[Brad Campbell]

Raid-6 did not create sysfs entries for stripe cache

Signed-off-by: Brad Campbell <brad@wasp.net.au>

---
diff -u vanilla/linux-2.6.16/drivers/md/raid6main.c linux-2.6.16/drivers/md/raid6main.c
--- vanilla/linux-2.6.16/drivers/md/raid6main.c 2006-03-20 09:53:29.000000000 +0400
+++ linux-2.6.16/drivers/md/raid6main.c 2006-03-25 16:35:05.000000000 +0400
@@ -2148,6 +2148,7 @@
         }

         /* Ok, everything is just fine now */
+        sysfs_create_group(&mddev->kobj, &raid6_attrs_group);
         mddev->array_size =  mddev->size * (mddev->raid_disks - 2);

         mddev->queue->unplug_fn = raid6_unplug_device;
---

-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

Re: [PATCH] Add stripe cache entries to raid6 sysfs

[Neil Brown]

On Saturday March 25, brad@wasp.net.au wrote:
> Raid-6 did not create sysfs entries for stripe cache
> 
> Signed-off-by: Brad Campbell <brad@wasp.net.au>
> 
> ---
> diff -u vanilla/linux-2.6.16/drivers/md/raid6main.c linux-2.6.16/drivers/md/raid6main.c
> --- vanilla/linux-2.6.16/drivers/md/raid6main.c 2006-03-20 09:53:29.000000000 +0400
> +++ linux-2.6.16/drivers/md/raid6main.c 2006-03-25 16:35:05.000000000 +0400
> @@ -2148,6 +2148,7 @@
>          }
> 
>          /* Ok, everything is just fine now */
> +        sysfs_create_group(&mddev->kobj, &raid6_attrs_group);
>          mddev->array_size =  mddev->size * (mddev->raid_disks - 2);
> 
>          mddev->queue->unplug_fn = raid6_unplug_device;

Gee, I wonder I missed that...
Thanks!

NeilBrown