* Stripe dirty bitmap
@ 2010-07-05 0:26 Bill Davidsen
2010-07-05 1:02 ` Neil Brown
0 siblings, 1 reply; 3+ messages in thread
From: Bill Davidsen @ 2010-07-05 0:26 UTC (permalink / raw)
To: Linux RAID
Sure would be nice to have md track whole never written stripes, so
creating an array didn't have to be done over a three day weekend. When
any part of a virgin stripe was written it could then be initialized
properly, and when a virgin stripe was read zeros could be returned
without disk i/o. It doesn't matter that the reads are done in parallel,
with modern disk the bus is the bottleneck. With eSATA arrays the bus is
slow to start with, passing TB through it should be avoided if possible.
--
Bill Davidsen <davidsen@tmr.com>
"We can't solve today's problems by using the same thinking we
used in creating them." - Einstein
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Stripe dirty bitmap
2010-07-05 0:26 Stripe dirty bitmap Bill Davidsen
@ 2010-07-05 1:02 ` Neil Brown
2010-07-05 1:24 ` Bill Davidsen
0 siblings, 1 reply; 3+ messages in thread
From: Neil Brown @ 2010-07-05 1:02 UTC (permalink / raw)
To: Bill Davidsen; +Cc: Linux RAID
On Sun, 04 Jul 2010 20:26:40 -0400
Bill Davidsen <davidsen@tmr.com> wrote:
> Sure would be nice to have md track whole never written stripes, so
> creating an array didn't have to be done over a three day weekend. When
> any part of a virgin stripe was written it could then be initialized
> properly, and when a virgin stripe was read zeros could be returned
> without disk i/o. It doesn't matter that the reads are done in parallel,
> with modern disk the bus is the bottleneck. With eSATA arrays the bus is
> slow to start with, passing TB through it should be avoided if possible.
>
Sure would.
NeilBrown
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Stripe dirty bitmap
2010-07-05 1:02 ` Neil Brown
@ 2010-07-05 1:24 ` Bill Davidsen
0 siblings, 0 replies; 3+ messages in thread
From: Bill Davidsen @ 2010-07-05 1:24 UTC (permalink / raw)
To: Neil Brown; +Cc: Linux RAID
Neil Brown wrote:
> On Sun, 04 Jul 2010 20:26:40 -0400
> Bill Davidsen <davidsen@tmr.com> wrote:
>
>
>> Sure would be nice to have md track whole never written stripes, so
>> creating an array didn't have to be done over a three day weekend. When
>> any part of a virgin stripe was written it could then be initialized
>> properly, and when a virgin stripe was read zeros could be returned
>> without disk i/o. It doesn't matter that the reads are done in parallel,
>> with modern disk the bus is the bottleneck. With eSATA arrays the bus is
>> slow to start with, passing TB through it should be avoided if possible.
>>
>>
>
> Sure would.
>
Have to have a copy on each drive, I think? Use a bit for a group of N
stripes or one per stripe? Put N in the metadata?
I'd use stripe_cache_size, but that changes.
As disk gets cheap (1.5TB for $65 this weekend?) bus speed is being an
issue, more so with software raid which does the io out of system memory.
--
Bill Davidsen <davidsen@tmr.com>
"We can't solve today's problems by using the same thinking we
used in creating them." - Einstein
^ permalink raw reply [flat|nested] 3+ messages in thread
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2010-07-05 0:26 Stripe dirty bitmap Bill Davidsen
2010-07-05 1:02 ` Neil Brown
2010-07-05 1:24 ` Bill Davidsen
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