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Tue, 28 May 2024 14:49:42 -0700 (PDT) MIME-Version: 1.0 References: <16277.1716771974@lunacy.ugrad.cs.cmu.edu> <17169248040.5f383EFCe.47999@composer.9fans.topicbox.com> In-Reply-To: <17169248040.5f383EFCe.47999@composer.9fans.topicbox.com> From: Charles Forsyth Date: Tue, 28 May 2024 22:49:30 +0100 Message-ID: Subject: Re: [9fans] Throwing in the Towel To: 9fans <9fans@9fans.net> Content-Type: multipart/alternative; boundary=0000000000007edc5406198a9cfb Topicbox-Policy-Reasoning: allow: sender is a member Topicbox-Message-UUID: 34e3fa2a-1d3c-11ef-8b64-55f4fe8b7b06 Archived-At: =?UTF-8?B?PGh0dHBzOi8vOWZhbnMudG9waWNib3guY29tL2dyb3Vwcy85?= =?UTF-8?B?ZmFucy9UMmNhNjc0ODZjN2ExM2E3Ny1NZTY3YTRkNDNlNzJjZGEwYWE4Nzhm?= =?UTF-8?B?YzIxPg==?= List-Help: List-Id: "9fans" <9fans.9fans.net> List-Post: List-Software: Topicbox v0 List-Subscribe: Precedence: list Reply-To: 9fans <9fans@9fans.net> Content-Transfer-Encoding: 7bit List-Unsubscribe: , Topicbox-Delivery-ID: 2:9fans:437d30aa-c441-11e9-8a57-d036212d11b0:522be890-2105-11eb-b15e-8d699134e1fa:Me67a4d43e72cda0aa878fc21:1:dpVAJbf2Ogikxo6WHSkCtkbu3xvWiUHnafGI413led0 --0000000000007edc5406198a9cfb Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable i'm curious what straightforward storage structure wouldn't be. trying to second-guess ssd firmware seems a tricky design criterion. On Tue, 28 May 2024 at 20:34, wrote: > For the napkin calculation: On disk, the IEntry is 38Bytes. Alas, writes > occur always in (the ssd internal) blocksize. So, essentially (assuming > 4096 byte blocksize, which is quite optimistic), we have a write efficien= cy > of less than 1 percent. > > A good firmware in the ssd could avoid needing a new block for the write, > if all bits are changed in teh same direction by the new data. This is > defeated by the binary search in the index buckets. The entries must be > sorted, and the number of used entries is tob updated. So, for each new > entry the whole (internal) block has to be remapped. Therefore an erasure > block must be erased after about 1m/4k index writes. > > It seems, venti in its current form is a ssd killer, if they are used for > the isects. > *9fans * / 9fans / see discussions > + participants > + delivery options > Permalink > > ------------------------------------------ 9fans: 9fans Permalink: https://9fans.topicbox.com/groups/9fans/T2ca67486c7a13a77-Me67a4= d43e72cda0aa878fc21 Delivery options: https://9fans.topicbox.com/groups/9fans/subscription --0000000000007edc5406198a9cfb Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
i'm curious what straightforward storage s= tructure wouldn't be. trying to second-guess ssd firmware seems a = tricky design criterion.

On Tue, 28 May 2024 at 20:34, <wb.kloke@gmail.com> wrote:
For the napki= n calculation: On disk, the IEntry is 38Bytes. Alas, writes occur always in= (the ssd internal) blocksize. So, essentially (assuming 4096 byte blocksiz= e, which is quite optimistic), we have a write efficiency of less than 1 pe= rcent.

A good firmware in the ssd could av= oid needing a new block for the write, if all bits are changed in teh same = direction by the new data. This is defeated by the binary search in the ind= ex buckets. The entries must be sorted, and the number of used entries is t= ob updated. So, for each new entry the whole (internal) block has to be rem= apped. Therefore an erasure block must be erased after about  1m/4k in= dex writes.

It seems, venti in its current= form is a ssd killer, if they are used for the isects.
= --0000000000007edc5406198a9cfb--