Hard Drives - Revision history

Leo at 00:47, 15 June 2020

2020-06-15T00:47:48Z

← Older revision		Revision as of 00:47, 15 June 2020
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	The major players now are: Seagate, Western Digital, and Toshiba.		The major players now are: Seagate, Western Digital, and Toshiba.

			{{Navbox Hardware}}[[Category:Hardware]]

Leo: /* SMR */

2020-04-20T03:17:11Z

SMR

← Older revision		Revision as of 03:17, 20 April 2020
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	== SMR ==		== SMR ==
	'''Shingled Magnetic Recording''' ('''SMR''') drives writes tracks that partially overlap to increase the number of tracks per platter. ~~Writes to SMR will requires~~ the ~~firmware~~ to ~~determine if adjacent tracks need~~ rewriting~~. If the adjacent track contains valid~~ data~~, it must~~ also ~~be rewritten. This process repeats for every subsequent track and causes an 'avalanche'~~ of ~~rewrites and results in poor write performance~~. ~~'''Drive-managed SMR''' ('''DM-~~SMR~~''')~~ drives ~~mask~~ the ~~poor write performance by caching writes~~ to a ~~non-SMR portion of~~ the disk ~~and then rewriting~~ to ~~shingled area of~~ the ~~disk when idle. Read~~ performance ~~of SMR is equivalent to non-shingled tracks (using perpendicular recording) on '''Conventional Magnetic Recording''' ('''CMR''') drives~~.		'''Shingled Magnetic Recording''' ('''SMR''') drives writes tracks that partially overlap to increase the number of tracks per platter. The designed usage is for write once, read many (WORM) data since the cost of re-writing data is significant. Similar to a SSD, rewriting data also requires rewriting a larger superset of the data. In the case of SMR drives, tracks adjacent to the data being rewritten as well as adjacent tracks to those tracks need to be rewritten. As such, a rewrite operation will require the disk to re-read all affected tracks before the entire affected section is rewritten resulting in high latency and poor performance.

	~~When using~~ SMR ~~with RAID arrays or ZFS RAIDZ datasets, mixing it with~~ non-SMR ~~drives~~ may cause ~~unexpected results such as~~ the array ~~failing or disks being kicked out~~.		'''Drive-managed SMR''' ('''DM-SMR''') drives mask the poor write performance by buffering writes to a non-SMR portion of the disk and then rewriting to shingled area of the disk when idle. Under heavy writes, this buffer may fill up and results in very time consuming write operations. The sudden decrease in write performance and substantial increase in disk latency especially when resilvering can cause certain RAID arrays to think the disk is faulty or failing and removes it from the array.

	~~Western Digital Reds are DM-SMR~~ (~~https://blocksandfiles.com/2020/04/14/wd-red-nas-drives-shingled-magnetic-recording/~~) ~~which may cause issues in NAS applications that require high random IO. Some newer Seagate Barracuda and Desktop hard~~ drives are ~~also DM-SMR (https://blocksandfiles.com/2020/04/15/seagate-2-4-and-8tb-barracuda-and-desktop-hdd-smr/)~~.		Although read performance is typically similar to that of '''Conventional Magnetic Recording''' ('''CMR''') drives, it isn't always the case especially when write operations are in progress.

	DM-~~SMR or~~ SMR drives can be detected if ~~smartctl reports the~~ drive ~~supporting~~ the TRIM function. (https://github.com/openzfs/zfs/issues/10182)		More recently, Western Digital and Seagate have admitted to using SMR on disks that were not advertised as SMR. Western Digital Reds which are promoted for NAS applications are also included and have resulted in many unhappy users. See also:
			* https://blocksandfiles.com/2020/04/14/wd-red-nas-drives-shingled-magnetic-recording/
			* https://blocksandfiles.com/2020/04/15/seagate-2-4-and-8tb-barracuda-and-desktop-hdd-smr/
			* https://hardware.slashdot.org/story/20/04/19/0432229/storage-vendors-are-quietly-slipping-smr-disks-into-consumer-hard-drives#comments

			Some claim that WD SMR drives can be detected if a normal hard drive supports the TRIM function. See: https://github.com/openzfs/zfs/issues/10182

	== Manufacturers ==		== Manufacturers ==

Leo at 18:17, 15 April 2020

2020-04-15T18:17:37Z

← Older revision		Revision as of 18:17, 15 April 2020
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	== SMR ==		== SMR ==
	Shingled Magnetic Recording (SMR) drives writes tracks that partially overlap to increase the number of tracks per platter. Writes to SMR will ~~require~~ rewriting ~~overlapping tracks resulting~~ in poor write performance. Drive-managed SMR (DM-SMR) drives mask the poor write performance by caching writes to a non-SMR portion of the disk and then rewriting to shingled area of the disk when idle. Read performance of SMR is equivalent to non-shingled Conventional Magnetic Recording (CMR).		'''Shingled Magnetic Recording''' ('''SMR''') drives writes tracks that partially overlap to increase the number of tracks per platter. Writes to SMR will requires the firmware to determine if adjacent tracks need rewriting. If the adjacent track contains valid data, it must also be rewritten. This process repeats for every subsequent track and causes an 'avalanche' of rewrites and results in poor write performance. '''Drive-managed SMR''' ('''DM-SMR''') drives mask the poor write performance by caching writes to a non-SMR portion of the disk and then rewriting to shingled area of the disk when idle. Read performance of SMR is equivalent to non-shingled tracks (using perpendicular recording) on '''Conventional Magnetic Recording''' ('''CMR''') drives.

	When using SMR with RAID arrays or ZFS RAIDZ datasets, mixing it with non-SMR drives may cause unexpected results such as the array failing or disks being kicked out.		When using SMR with RAID arrays or ZFS RAIDZ datasets, mixing it with non-SMR drives may cause unexpected results such as the array failing or disks being kicked out.

Leo at 18:03, 15 April 2020

2020-04-15T18:03:03Z

← Older revision		Revision as of 18:03, 15 April 2020
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	Western Digital Reds are DM-SMR (https://blocksandfiles.com/2020/04/14/wd-red-nas-drives-shingled-magnetic-recording/) which may cause issues in NAS applications that require high random IO. Some newer Seagate Barracuda and Desktop hard drives are also DM-SMR (https://blocksandfiles.com/2020/04/15/seagate-2-4-and-8tb-barracuda-and-desktop-hdd-smr/).		Western Digital Reds are DM-SMR (https://blocksandfiles.com/2020/04/14/wd-red-nas-drives-shingled-magnetic-recording/) which may cause issues in NAS applications that require high random IO. Some newer Seagate Barracuda and Desktop hard drives are also DM-SMR (https://blocksandfiles.com/2020/04/15/seagate-2-4-and-8tb-barracuda-and-desktop-hdd-smr/).

			DM-SMR or SMR drives can be detected if smartctl reports the drive supporting the TRIM function. (https://github.com/openzfs/zfs/issues/10182)

			== Manufacturers ==
			See: https://en.wikipedia.org/wiki/List_of_defunct_hard_disk_manufacturers

			The major players now are: Seagate, Western Digital, and Toshiba.

Leo: Created page with " == SMR == Shingled Magnetic Recording (SMR) drives writes tracks that partially overlap to increase the number of tracks per platter. Writes to SMR will require rewriting ove..."

2020-04-15T17:40:21Z

Created page with " == SMR == Shingled Magnetic Recording (SMR) drives writes tracks that partially overlap to increase the number of tracks per platter. Writes to SMR will require rewriting ove..."

New page

== SMR ==
Shingled Magnetic Recording (SMR) drives writes tracks that partially overlap to increase the number of tracks per platter. Writes to SMR will require rewriting overlapping tracks resulting in poor write performance. Drive-managed SMR (DM-SMR) drives mask the poor write performance by caching writes to a non-SMR portion of the disk and then rewriting to shingled area of the disk when idle. Read performance of SMR is equivalent to non-shingled Conventional Magnetic Recording (CMR).

When using SMR with RAID arrays or ZFS RAIDZ datasets, mixing it with non-SMR drives may cause unexpected results such as the array failing or disks being kicked out.

Western Digital Reds are DM-SMR (https://blocksandfiles.com/2020/04/14/wd-red-nas-drives-shingled-magnetic-recording/) which may cause issues in NAS applications that require high random IO. Some newer Seagate Barracuda and Desktop hard drives are also DM-SMR (https://blocksandfiles.com/2020/04/15/seagate-2-4-and-8tb-barracuda-and-desktop-hdd-smr/).