Actual number of writes to a MTD device

Actual number of writes to a MTD device

[Kartik Nagar]

Hi,

I am using UBIFS on top of UBI on top of a MTD partition and then running some
workloads on the UBIFS filesystem. I actually want to determine the write
amplification factor for the workload, for which i need the actual number of
writes going to the MTD device. Do UBIFS/MTD systems record such statistics, or
will I have to make changes to the source code to obtain the statistics?

RE: Actual number of writes to a MTD device

[Atlant Schmidt]

Kartik:

  I don't know if the UBI or MTD layers keep such
  statistics directly, but over time, you can
  certainly *INFER* such statistics: just watch
  the erase counters. Because no flash area can
  be written more than once without erasing, you
  can be sure that if you see the sum of all of
  the erase counters increase by "n", then you have
  written approximately (n * bytes_per_LEB) bytes
  of data.

  This is only valid when measured over a reasonably
  long time, of course. Over a short time, there's
  too much "noise" in the signal because slight
  variations in the LEB-to-PEB mapping can cause
  big variations in exactly when erase blocks get
  erased.

                       Atlant

-----Original Message-----
From: linux-mtd-bounces@lists.infradead.org [mailto:linux-mtd-bounces@lists.infradead.org] On Behalf Of Kartik Nagar
Sent: Saturday, April 23, 2011 08:56
To: linux-mtd@lists.infradead.org
Subject: Actual number of writes to a MTD device

Hi,

I am using UBIFS on top of UBI on top of a MTD partition and then running some
workloads on the UBIFS filesystem. I actually want to determine the write
amplification factor for the workload, for which i need the actual number of
writes going to the MTD device. Do UBIFS/MTD systems record such statistics, or
will I have to make changes to the source code to obtain the statistics?


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Re: Actual number of writes to a MTD device

[Artem Bityutskiy]

On Sat, 2011-04-23 at 12:55 +0000, Kartik Nagar wrote:
> Hi,
> 
> I am using UBIFS on top of UBI on top of a MTD partition and then running some
> workloads on the UBIFS filesystem. I actually want to determine the write
> amplification factor for the workload, for which i need the actual number of
> writes going to the MTD device. Do UBIFS/MTD systems record such statistics, or
> will I have to make changes to the source code to obtain the statistics?

These statistics has to be done on MTD level, not in UBIFS. MTD does not
do this AFAIK.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)