From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nebojsa Trpkovic Subject: Re: TLER / CCTL timeout handling Date: Thu, 25 Mar 2010 01:48:40 +0100 Message-ID: <4BAAB2E8.2040104@gmail.com> References: <4BA93C3F.2070208@gmail.com> <4BAA8A21.8050601@stud.tu-ilmenau.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <4BAA8A21.8050601@stud.tu-ilmenau.de> Sender: linux-raid-owner@vger.kernel.org To: st0ff@npl.de Cc: =?ISO-8859-15?Q?Stefan_/*St0fF*/_H=FCbner?= , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 03/24/10 22:54, Stefan /*St0fF*/ H=FCbner wrote: > Am 23.03.2010 23:10, schrieb Nebojsa Trpkovic: >> Hello. >> >> I've found interesting text about TLER / CCTL >> (http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery ) >=20 > You might want to read on inside the ATA8-ACS, section about SCT Tran= sport. >> >> on desktop class drives: >> http://forums.storagereview.com/index.php/topic/28333-tler-cctl/ >> >> So, the question is: >> >> If I make my drive report back it failed to read the requested secto= r, >> how that report will be handeled? >=20 > As far as I understood in recent answers to my questions: as expected= =2E >> >> Will Linux software RAID be aware of that report and start some acti= on >> (rebuilding affected stripe or at least whole array, reallocating ba= d >> sectors along the way) ? >> > Indeed. Michael Tokarev answered to me on 2/9/10: > "On failed _read_ it tries to > reconstruct data from other disk drives and writes the reconstructed > data back to the drive where read failed. If the _write_ fails md wi= ll > drop the disk." >=20 > This means: if read fails and the drive does not report back, the > following reconstructing write calls will fail, too. The disk gets > dropped, because it (most probably) is still doing its error recovery= on > the former read request and by that not responding. >=20 > If you enable ERC read timeouts, it'll report a media error (or > something similar), but honour the write request. If you give the ER= C > write timeout a value that is not too small and also not too large (i= =2Ee. > it shouldn't timeout the write-operation from the view of the kernel)= , > it will either fix the pending sector, or reallocate it. If the ERC > write timeout value is too small, it'll very aggressively reallocate > sectors - which should not be the intention, as there are very few sp= are > sectors (compared to the amount of sectors in total - only a few thou= sand). >> >> Thank you. >> Nebojsa Trpkovic >=20 > You're welcome, and all the best, > Stefan >=20 Thank you very much! This is great answer (explaining a lot of things) and great news (there's nothing to worry/hack about). So, now we (desktop drives users) just have to wait for smartmontools 5.40 or pull source from SVN and set some reasonable ERC read timeouts. Is value of 7 seconds considered as reasonable ERC read timeout? Nebojsa -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html