From: <jos...@vi...> - 2004-05-17 18:03:55
|
I have been thinking about what you have said about bad sectors. And I feel the conclusion I got to wich may be wrong is that at all times raid 1 should be used if we can't handle the risk of a bad sector. The thing is, on machines with one drive and stand alone, one must create= a raid1 setup using diferent partitions of the same drive. But another question remains, does software raid in linux when one of the partitions gives an error read from the other and writes back to the one that gave the error? Does it alone mark unrecoverable bad sectors without the need for user intervention? Thanks, Jos=E9 Faria |
From: <jos...@vi...> - 2004-05-18 18:02:55
|
Hi folks, I have been discussing a very important subject on the smartmontools mail= ing list: data corruption. So, one thing leads to another and we came to evms, so we need to know a = few things about it... 1) In raid 1 when a drive cannot read a block (may be a temporary failure= ), evms reads from the other drive, but then does it write back the block to the first drive or not? I guess it does and if the block isn't okay then he relocates it, correct= ? 2) Does evms has any way of ensuring that the data read is the same writt= en, (CRC?)? 3) Does evms can be used to create a raid1 set using two partitions of th= e same drive (for laptops) to cover the problem pointed in 1? I'm sorry if the answers to these questions are too obvious for you guys, but for some of us they aren't. Thanks a lot, keep up the very good work. Jos=E9 Faria |
From: Bruce A. <ba...@gr...> - 2004-05-17 20:17:19
|
Hi Jose, > I have been thinking about what you have said about bad sectors. > > And I feel the conclusion I got to wich may be wrong is that at all times > raid 1 should be used if we can't handle the risk of a bad sector. > > The thing is, on machines with one drive and stand alone, one must create a > raid1 setup using diferent partitions of the same drive. Of course this runs the risk of total data loss if the drive fails. Can you afford THAT risk? > But another question remains, does software raid in linux when one of > the partitions gives an error read from the other and writes back to > the one that gave the error? It's a good question to ask the software RAID maintainers. Could you ask them and let us know? > Does it alone mark unrecoverable bad sectors without the need for user > intervention? It wouldn't need to do this, if it writes back to the sector that gave an error. Writing back to that sector will force reallocation to take place. Cheers, Bruce |
From: <jos...@vi...> - 2004-05-18 17:54:35
|
So far I have found out, That there are two diferent types of software raid in linux, md and evms. While md is quite stable its in a standstill, and doesn't support bad blo= ck relocation. Evms is under greater activity and does support bad block relocation. So I guess it does suppor it... But hey, I asking those dudes, I got thei= r email.. Be back, Jos=E9 Faria ----- Original Message -----=20 From: Bruce Allen To: Jos=E9 Alexandre Antunes Faria Cc: sma...@li... Sent: Monday, May 17, 2004 9:17 PM Subject: Re: [smartmontools-support]Data corruption Hi Jose, > I have been thinking about what you have said about bad sectors. > > And I feel the conclusion I got to wich may be wrong is that at all tim= es > raid 1 should be used if we can't handle the risk of a bad sector. > > The thing is, on machines with one drive and stand alone, one must crea= te a > raid1 setup using diferent partitions of the same drive. Of course this runs the risk of total data loss if the drive fails. Can you afford THAT risk? > But another question remains, does software raid in linux when one of > the partitions gives an error read from the other and writes back to > the one that gave the error? It's a good question to ask the software RAID maintainers. Could you ask them and let us know? > Does it alone mark unrecoverable bad sectors without the need for user > intervention? It wouldn't need to do this, if it writes back to the sector that gave an error. Writing back to that sector will force reallocation to take place. Cheers, Bruce ------------------------------------------------------- This SF.Net email is sponsored by: SourceForge.net Broadband Sign-up now for SourceForge Broadband and get the fastest 6.0/768 connection for only $19.95/mo for the first 3 months! http://ads.osdn.com/?ad_id=3D2562&alloc_id=3D6184&op=3Dclick _______________________________________________ Smartmontools-support mailing list Sma...@li... https://lists.sourceforge.net/lists/listinfo/smartmontools-support |
From: Bruce A. <ba...@gr...> - 2004-05-18 19:40:31
|
Hi Jose, > While md is quite stable its in a standstill, and doesn't support bad > block relocation. I think that this is the wrong question to ask. Md doesn't need to relocate bad blocks. It only needs to write valid data to bad blocks. The underlying physical disk will then take care of any relocation, in a way that's not visible to md. Bruce |