Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi Lars, What are you using to interconnect the two DRBD systems? Loss of half of performance seems excessive. I usually get about 95% of the arrays sustained write performance and multiple arrays can synch at once without penalty. Rob -----Original Message----- From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of Tomasz Chmielewski Sent: 19 January 2009 09:54 To: Lars Täuber Cc: drbd-user at lists.linbit.com Subject: Re: [DRBD-user] slow sync speed of 12TB over 10GE Lars Täuber schrieb: > 6553600000 bytes (6.6 GB) copied, 25.4397 s, 258 MB/s > md4 72164,00 0,00 288656,00 0 288656 > > The numbers are floating between ~18900 and ~23400. > > Should I really mount the device with a filesystem on it? The last tests were made without a filesystem too. Linear writes to a raw device are different to writes to a filesystem because: - you don't have to update metadata, journal etc., so you can write faster - raw device can not be fragmented, where a filesystem can (heads in your HDD won't jump here and there) Technically speaking, such writes: [==============>.....] sync'ed: 76.4% (242356/1023804)K finish: 0:00:01 speed: 130,240 (130,240) K/sec can be also fragmented as well - some area can be out of sync here, some area there - the head will jump. Also, note that at the same time there can be real writes to that device (i.e., something writes to your /dev/drbdXY device) - it will impact the speed of that sync because those writes have to be synchronized as well; also HDD head will jump more often. It's hard to tell if such difference (258 MB/s dd write speed versus 130 MB/s DRBD sync) can be explained by only those items I mentioned. -- Tomasz Chmielewski http://wpkg.org _______________________________________________ drbd-user mailing list drbd-user at lists.linbit.com http://lists.linbit.com/mailman/listinfo/drbd-user The SAQ Group Registered Office: 18 Chapel Street, Petersfield, Hampshire GU32 3DZ SAQ is the trading name of SEMTEC Limited. Registered in England & Wales Company Number: 06481952 http://www.saqnet.co.uk AS29219 SAQ Group Delivers high quality, honestly priced communication and I.T. services to UK Business. Broadband : Domains : Email : Hosting : CoLo : Servers : Racks : Transit : Backups : Managed Networks : Remote Support. ISPA Member Find us in http://www.thebestof.co.uk/petersfield