Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-15 Thread Edgar Fuß
JLRG> 1- There is no need to use parity map for the RAID 1/10/5/6. Usually JLRG> the impact is small, but it can be noticeable in busy servers. EF> I don't notice it. JLRG> When there is a crash, the time to rebuild the raid < 1min? I said I didn't notice an impact. Of course I do notice a massive

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-14 Thread Thor Lancelot Simon
On Wed, Sep 14, 2016 at 03:16:13PM +, Eduardo Horvath wrote: > On Wed, 14 Sep 2016, Edgar Fu? wrote: > > > > 2- In scattered writes contained in a same slice, it allows to reduce > > > the number of writes. With RAID 5/6 there is a advantage, the parity > > > is written only one time for

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-14 Thread Hauke Fath
On Wed, 14 Sep 2016 13:54:34 +0200, Edgar Fuß wrote: >> 4- Faster synchronous writes. > Y E S. > This is the only point I fully aggree on. We've had severe problems with > brain-dead software (Firefox, Dropbox) performing tons of synchronous 4K > writes (on a bs=16K FFS) which nearly killed us

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-14 Thread Jose Luis Rodriguez Garcia
>> 1- There is no need to use parity map for the RAID 1/10/5/6. Usually >> the impact is small, but it can be noticeable in busy servers. >I don't notice it. When there is a crash, the time to rebuild the raid < 1min? ... >rather large. A segment should match a slice (or a number of them) >I

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-14 Thread Eduardo Horvath
On Wed, 14 Sep 2016, Edgar Fu? wrote: > > 2- In scattered writes contained in a same slice, it allows to reduce > > the number of writes. With RAID 5/6 there is a advantage, the parity > > is written only one time for several writes in the same slice, instead > > of one time for every write in

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-14 Thread Manuel Bouyer
On Wed, Sep 14, 2016 at 01:54:34PM +0200, Edgar Fuß wrote: > [...] > I would suppose LFS to perform great on a RAIDframe. Isn't Manuel Bouyer > using this in production? No, I played with LFS at some point but I never used it in production. -- Manuel Bouyer

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-14 Thread Edgar Fuß
I'm using a 12TB RAIDframe Level 5 RAID (4+1 discs) in production. There are 150 people's home directories and mail on FFFs file systems on it. > 1- There is no need to use parity map for the RAID 1/10/5/6. Usually > the impact is small, but it can be noticeable in busy servers. I don't notice

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-11 Thread Jose Luis Rodriguez Garcia
On Sat, Sep 10, 2016 at 4:18 PM, Thor Lancelot Simon wrote: > On Fri, Sep 09, 2016 at 11:09:49PM +0200, Jose Luis Rodriguez Garcia wrote: >> B- It can use the buffer cache for avoid read/write cycles, and do >> only writes if the data to be read is in memory. > > I'd stay more

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-10 Thread David Holland
On Fri, Sep 09, 2016 at 11:09:49PM +0200, Jose Luis Rodriguez Garcia wrote: > This is a continuation of the thread Is factible to implement full > writes of stripes to raid using NVRAM memory in LFS. > http://mail-index.netbsd.org/tech-kern/2016/08/18/msg020982.html > > I want to discuss in

Re: What is the best layer/device for a write-back cache based in nvram?

2016-09-10 Thread Thor Lancelot Simon
On Fri, Sep 09, 2016 at 11:09:49PM +0200, Jose Luis Rodriguez Garcia wrote: > > The proposed layer must support: > > A- It must be able to obtain the raid configuration of the raid device > backing the writeback cache. If it is a RAID 0/1 it will cache > portions of the size of the interleave.